1) Mycoplasmas are bacteria that lack cell walls. On the basis of this structural feature, which statement concerning mycoplasmas should be true?
A) They are gram-negative.
B) They are subject to lysis in hypotonic conditions.
C) They lack a cell membrane as well.
D) They should contain less cellulose than do bacteria that possess cell walls.
E) They possess typical prokaryotic flagella.
Answer: B
2) Though plants, fungi, and prokaryotes all have cell walls, we place them in different taxa. Which of these observations comes closest to explaining the basis for placing these organisms in different taxa, well before relevant data from molecular systematics became available?
A) Some closely resemble animals, which lack cell walls.
B) Their cell walls are composed of very different biochemicals.
C) Some have cell walls only for support.
D) Some have cell walls only for protection from herbivores.
E) Some have cell walls only to control osmotic balance.
Answer: B
3) Which statement about bacterial cell walls is false?
A) Bacterial cell walls differ in molecular composition from plant cell walls.
B) Cell walls prevent cells from bursting in hypotonic environments.
C) Cell walls prevent cells from dying in hypertonic conditions.
D) Bacterial cell walls are similar in function to the cell walls of many protists, fungi, and plants.
E) Cell walls provide the cell with a degree of physical protection from the environment.
Answer: C
4) The predatory bacterium, Bdellovibrio bacteriophorus, drills into a prey bacterium and, once inside, digests it. In an attack upon a gram-negative bacterium that has a slimy cell covering, what is the correct sequence of structures penetrated by B. bacteriophorus on its way to the prey's cytoplasm?
1. membrane composed mostly of lipopolysaccharide
2. membrane composed mostly of phospholipids
3. peptidoglycan
4. capsule
A) 2, 4, 3, 1
B) 1, 3, 4, 2
C) 1, 4, 3, 2
D) 4, 1, 3, 2
E) 4, 3, 1, 2
Answer: D
5) Jams, jellies, preserves, honey, and other foodstuffs with high sugar content hardly ever become contaminated by bacteria, even when the food containers are left open at room temperature. This is because bacteria that encounter such an environment
A) undergo death by plasmolysis.
B) are unable to metabolize the glucose or fructose, and thus starve to death.
C) experience lysis.
D) are obligate anaerobes.
E) are unable to swim through these thick and viscous materials.
Answer: A
6) In a bacterium that possesses antibiotic resistance and the potential to persist through very adverse conditions, such as freezing, drying, or high temperatures, DNA should be located within, or be part of, which structures?
1. nucleoid region
2. endospore
3. fimbriae
4. plasmids
A) 1 only
B) 1 and 2 only
C) 1 and 4 only
D) 2 and 4 only
E) 1, 2, and 4
Answer: E
7) Which two structures play direct roles in permitting bacteria to adhere to each other, or to other surfaces?
1. capsules
2. endospores
3. fimbriae
4. plasmids
5. flagella
A) 1 and 2
B) 1 and 3
C) 2 and 3
D) 3 and 4
E) 3 and 5
Answer: B
8) The typical prokaryotic flagellum features
A) an internal 9 + 2 pattern of microtubules.
B) an external covering provided by the plasma membrane.
C) a complex "motor" embedded in the cell wall and plasma membrane.
D) a basal body that is similar in structure to the cell's centrioles.
E) a membrane-enclosed organelle with motor proteins.
Answer: C
9) Prokaryotic ribosomes differ from those present in eukaryotic cytosol. Because of this, which of the following is correct?
A) Some antibiotics can block protein synthesis in bacteria without effects in the eukaryotic host.
B) Eukaryotes did not evolve from prokaryotes.
C) Translation can occur at the same time as transcription in eukaryotes but not in prokaryotes.
D) Some antibiotics can block the synthesis of peptidoglycan in the walls of bacteria.
E) Prokaryotes are able to use a much greater variety of molecules as food sources than can eukaryotes.
Answer: A
10) Which statement about the genomes of prokaryotes is correct?
A) Prokaryotic genomes are diploid throughout most of the cell cycle.
B) Prokaryotic chromosomes are sometimes called plasmids.
C) Prokaryotic cells have multiple chromosomes, "packed" with a relatively large amount of protein.
D) The prokaryotic chromosome is not contained within a nucleus but, rather, is found at the nucleolus.
E) Prokaryotic genomes are composed of circular DNA.
Answer: E
11) If a bacterium regenerates from an endospore that did not possess any of the plasmids that were contained in its original parent cell, the regenerated bacterium will probably also
A) lack antibiotic-resistant genes.
B) lack a cell wall.
C) lack a chromosome.
D) lack water in its cytoplasm.
E) be unable to survive in its normal environment.
Answer: A
12) Although not present in all bacteria, this cell covering often enables cells that possess it to resist the defenses of host organisms, especially their phagocytic cells.
A) endospore
B) sex pilus
C) cell wall
D) capsule
Answer: D
13) Prokaryotes' essential genetic information is located in the
A) nucleolus.
B) nucleoid.
C) nucleosome.
D) plasmids.
E) exospore.
Answer: B
14) Which of the following is an important source of endotoxin in gram-negative species?
A) endospore
B) sex pilus
C) flagellum
D) cell wall
E) capsule
Answer: D
15) Chloramphenicol is an antibiotic that targets prokaryotic (70S) ribosomes, but not eukaryotic (80S) ribosomes. Which of these questions stems from this observation, plus an understanding of eukaryotic origins?
A) Can chloramphenicol also be used to control human diseases that are caused by archaeans?
B) Can chloramphenicol pass through the capsules possessed by many cyanobacteria?
C) If chloramphenicol inhibits prokaryotic ribosomes, should it not also inhibit mitochondrial ribosomes?
D) Why aren't prokaryotic ribosomes identical to eukaryotic ribosomes?
E) How is translation affected in ribosomes that are targeted by chloramphenicol?
Answer: C
16) In a hypothetical situation, the genes for sex pilus construction and for tetracycline resistance are located together on the same plasmid within a particular bacterium. If this bacterium readily performs conjugation involving a copy of this plasmid, then the result should be
A) a bacterium that has undergone transduction.
B) the rapid spread of tetracycline resistance to other bacteria in that habitat.
C) the subsequent loss of tetracycline resistance from this bacterium.
D) the production of endospores among the bacterium's progeny.
E) the temporary possession by this bacterium of a completely diploid genome.
Answer: B
17) Regarding prokaryotic genetics, which statement is correct?
A) Crossing over during prophase I introduces some genetic variation.
B) Prokaryotes feature the union of haploid gametes, as do eukaryotes.
C) Prokaryotes exchange some of their genes by conjugation, the union of haploid gametes, and transduction.
D) Mutation is a primary source of variation in prokaryote populations.
E) Prokaryotes skip sexual life cycles because their life cycle is too short.
Answer: D
18) Which of these statements about prokaryotes is correct?
A) Bacterial cells conjugate to mutually exchange genetic material.
B) Their genetic material is confined within vesicles known as plasmids.
C) They divide by binary fission, without mitosis or meiosis.
D) The persistence of bacteria throughout evolutionary time is due to their genetic homogeneity (in other words, sameness).
E) Genetic variation in bacteria is not known to occur, because of their asexual mode of reproduction.
Answer: C
19) Which of the following is least associated with the others?
A) horizontal gene transfer
B) genetic recombination
C) conjugation
D) transformation
E) binary fission
Answer: E
20) In Fred Griffith's experiments, harmless R strain pneumococcus became lethal S strain pneumococcus as the result of which of the following?
1. horizontal gene transfer
2. transduction
3. conjugation
4. transformation
5. genetic recombination
A) 2 only
B) 4 only
C) 2 and 5
D) 1, 3, and 5
E) 1, 4, and 5
Answer: E
21) Hershey and Chase performed an elegant experiment that convinced most biologists that DNA, rather than protein, was the genetic material. This experiment subjected bacteria to the same gene transfer mechanism as occurs in
A) transduction.
B) transformation.
C) conjugation.
D) binary fission.
E) endosymbiosis.
Answer: A
22) Match the numbered terms to the description that follows. Choose all appropriate terms.
1. autotroph
2. heterotroph
3. phototroph
4. chemotroph
a prokaryote that obtains both energy and carbon as it decomposes dead organisms
A) 1 only
B) 4 only
C) 1 and 3
D) 2 and 4
E) 1, 3, and 4
Answer: D
23) Match the numbered terms to the description that follows. Choose all appropriate terms.
1. autotroph
2. heterotroph
3. phototroph
4. chemotroph
an organism that obtains both carbon and energy by ingesting prey
A) 1 only
B) 4 only
C) 1 and 3
D) 2 and 4
E) 1, 3, and 4
Answer: D
24) Match the numbered terms to the description that follows. Choose all appropriate terms.
1. autotroph
2. heterotroph
3. phototroph
4. chemotroph
an organism that relies on photons to excite electrons within its membranes
A) 1 only
B) 3 only
C) 1 and 3
D) 2 and 4
E) 1, 3, and 4
Answer: B
25) Which of the following obtain energy by oxidizing inorganic substancesenergy that is used, in part, to fix CO₂?
A) photoautotrophs
B) photoheterotrophs
C) chemoautotrophs
D) chemoheterotrophs that perform decomposition
E) parasitic chemoheterotrophs
Answer: C
26) Mitochondria are thought to be the descendants of certain alpha proteobacteria. They are, however, no longer able to lead independent lives because most genes originally present on their chromosome have moved to the nuclear genome. Which phenomenon accounts for the movement of these genes?
A) plasmolysis
B) conjugation
C) translation
D) endocytosis
E) horizontal gene transfer
Answer: E
27) Carl Woese and collaborators identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?
A) microscopic examination of staining characteristics of the cell wall
B) metabolic characteristics such as the production of methane gas
C) metabolic characteristics such as chemoautotrophy and photosynthesis
D) genetic characteristics such as ribosomal RNA sequences
E) ecological characteristics such as the ability to survive in extreme environments
Answer: D
28) Which statement about the domain Archaea is true?
A) Genetic prospecting has recently revealed the existence of many previously unknown archaean species.
B) No archaeans can reduce CO₂ to methane.
C) The genomes of archaeans are unique, containing no genes that originated within bacteria.
D) No archaeans can inhabit solutions that are nearly 30% salt.
E) No archaeans are adapted to waters with temperatures above the boiling point.
Answer: A
29) If archaeans are more closely related to eukaryotes than to bacteria, then which of the following is a reasonable prediction?
A) Archaean DNA should have no introns.
B) Archaean chromosomes should have no protein bonded to them.
C) Archaean DNA should be single-stranded.
D) Archaean ribosomes should be larger than typical prokaryotic ribosomes.
E) Archaeans should lack cell walls.
Answer: D
30) Which of the following traits do archaeans and bacteria share?
1. composition of the cell wall
2. presence of plasma membrane
3. lack of a nuclear envelope
4. identical rRNA sequences
A) 1 only
B) 3 only
C) 1 and 3
D) 2 and 3
E) 2 and 4
Answer: D
31) Assuming that each of these possesses a cell wall, which prokaryotes should be expected to be most strongly resistant to plasmolysis in hypertonic environments?
A) extreme halophiles
B) extreme thermophiles
C) methanogens
D) cyanobacteria
E) nitrogen-fixing bacteria that live in root nodules
Answer: A
32) The thermoacidophile, Sulfolobus acidocaldarius, lacks peptidoglycan, but still possesses a cell wall. What is likely to be true of this species?
1. It is a bacterium.
2. It is an archaean.
3. The optimal pH of its enzymes will lie above pH 7.
4. The optimal pH of its enzymes will lie below pH 7.
5. It could inhabit certain hydrothermal springs.
6. It could inhabit alkaline hot springs.
A) 1, 3, and 6
B) 2, 4, and 6
C) 2, 4, and 5
D) 1, 3, and 5
E) 1, 4, and 5
Answer: C
33) A fish that has been salt-cured subsequently develops a reddish color. You suspect that the fish has been contaminated by the extreme halophile, Halobacterium. Which of these features of cells removed from the surface of the fish, if confirmed, would support your suspicion?
1. the presence of the same photosynthetic pigments found in cyanobacteria
2. cell walls that lack peptidoglycan
3. cells that are isotonic to conditions on the surface of the fish
4. cells containing bacteriorhodopsin
5. the presence of very large numbers of ion pumps in its plasma membrane
A) 2 and 5
B) 3 and 4
C) 1, 4, and 5
D) 3, 4, and 5
E) 2, 3, 4, and 5
Answer: E
34) The termite gut protist, Mixotricha paradoxa, has at least two kinds of bacteria attached to its outer surface. One kind is a spirochete that propels its host through the termite gut. A second type of bacteria synthesizes ATP, some of which is used by the spirochetes. The locomotion provided by the spirochetes introduces the ATP-producing bacteria to new food sources. Which term(s) is (are) applicable to the relationship between the two kinds of bacteria?
1. mutualism
2. parasitism
3. symbiosis
4. metabolic cooperation
A) 1 only
B) 1 and 2
C) 2 and 3
D) 1, 3, and 4
E) 2, 3, and 4
Answer: D
35) In general, what is the primary ecological role of prokaryotes?
A) parasitizing eukaryotes, thus causing diseases
B) breaking down organic matter
C) metabolizing materials in extreme environments
D) adding methane to the atmosphere
E) serving as primary producers in terrestrial environments
Answer: B
36) If all prokaryotes on Earth suddenly vanished, which of the following would be the most likely and most direct result?
A) The number of organisms on Earth would decrease by 1020%.
B) Human populations would thrive in the absence of disease.
C) Bacteriophage numbers would dramatically increase.
D) The recycling of nutrients would be greatly reduced, at least initially.
E) There would be no more pathogens on Earth.
Answer: D
37) In a hypothetical situation, a bacterium lives on the surface of a leaf, where it obtains nutrition from the leaf's nonliving, waxy covering while inhibiting the growth of other microbes that are plant pathogens. If this bacterium gains access to the inside of a leaf, however, it causes a fatal disease in the plant. Once the plant dies, the bacterium and its offspring decompose the plant. What is the correct sequence of ecological roles played by the bacterium in the situation described here? Use only those that apply.
1. nutrient recycler
2. mutualist
3. commensal
4.parasite
5. primary producer
A) 1, 3, 4
B) 2, 3, 4
C) 2, 4, 1
D) 1, 2, 5
E) 1, 2, 3
Answer: C
38) Foods can be preserved in many ways by slowing or preventing bacterial growth. Which of these methods should be least effective at inhibiting bacterial growth?
A) Refrigeration: slows bacterial metabolism and growth.
B) Closing previously opened containers: prevents more bacteria from entering, and excludes O₂.
C) Pickling: creates a pH at which most bacterial enzymes cannot function.
D) Canning in heavy sugar syrup: creates osmotic conditions that remove water from most bacterial cells.
E) Irradiation: kills bacteria by mutating their DNA to such an extent that their DNA-repair enzymes are overwhelmed.
Answer: B
39) Broad-spectrum antibiotics inhibit the growth of most intestinal bacteria. Consequently, assuming that nothing is done to counter the reduction of intestinal bacteria, a hospital patient who is receiving broad-spectrum antibiotics is most likely to become
A) unable to fix carbon dioxide.
B) antibiotic resistant.
C) unable to fix nitrogen.
D) unable to synthesize peptidoglycan.
E) deficient in certain vitamins and nutrients.
Answer: E
40. The following question refer to Figure .
In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
Which term best describes what has occurred among the experimental populations of cells over this eight-year period?
A) microevolution
B) speciation
C) adaptive radiation
D) sexual selection
E) stabilizing selection
Answer: A
41, In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
Which of the following, if it occurs in the absence of any other type of adaptation listed here, is least reasonable in terms of promoting bacterial survival over evolutionary time in a low-glucose environment?
A) increased efficiency at transporting glucose into the cell from the environment
B) increased ability to survive on simple sugars, other than glucose
C) increased ability to synthesize glucose from amino acid precursors
D) increased reliance on glycolytic enzymes
E) increased sensitivity to, and ability to move toward, whatever glucose is present in its habitat
Answer: D
42. In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
If the vertical axis of Figure 27.1 refers to "Darwinian fitness," then which of the following is the most valid and accurate measure of fitness?
A) number of daughter cells produced per mother cell per generation
B) amount of ATP generated per cell per unit time
C) average swimming speed of cells through the growth medium
D) amount of glucose synthesized per unit time
E) number of generations per unit time
Answer: E
43. In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
If new genetic variation in the experimental populations arose solely by spontaneous mutations, then the most effective process for subsequently increasing the prevalence of the beneficial mutations in the population over the course of generations is
A) transduction.
B) binary fission.
C) conjugation.
D) transformation.
E) meiosis.
Answer: B
44. In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
E. coli cells typically make most of their ATP by metabolizing glucose. Under the conditions of this experiment, what should be true of E. coli's generation time (especially early in the course of the experiment, but less so later on)?
A) Generation time should be the same as in the typical environment.
B) Generation time should be faster than in the typical environment.
C) Generation time should be slower than in the typical environment.
D) It is theoretically impossible to make any predictions about generation time under these conditions.
Answer: C
45. In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
If the experimental population of E. coli lacks an F factor or F plasmid, and if bacteriophages are excluded from the bacterial cultures, then which of these is (are) means by which beneficial mutations might be transmitted horizontally to other E. coli cells?
A) via sex pili
B) via transduction
C) via conjugation
D) via transformation
E) Two of the responses above are correct.
Answer: D
46. depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA). Use Figure to answer the following question.
What is occurring at Time C that is decreasing the DNA content?
A) crossing over
B) cytokinesis
C) meiosis
D) degradation of DNA that was not retained in the recipient's chromosome
E) reversal of the direction of conjugation
Answer: D
47. Figure depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA). Use Figure to answer the following question.
How is the recipient cell different at Time D than it was at Time A?
A) It has a greater number of genes.
B) It has a greater mass of DNA.
C) It has a different sequence of base pairs.
D) It contains bacteriophage DNA.
E) Its membrane-bound DNA pumps are inactive.
Answer: C
48 Figure depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA). Use Figure to answer the following question.
Which two processes are responsible for the shape of the curve at Time B?
1. transduction
2. entry of single-stranded Hfr DNA
3. rolling circle replication of single-stranded Hfr DNA
4. activation of DNA pumps in plasma membrane
A) 1 and 2
B) 1 and 4
C) 2 and 3
D) 2 and 4
E) 3 and 4
Answer: C
49. Figure Depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA). Use Figure to answer the following question.
During which two times can the recipient accurately be described as "recombinant" due to the sequence of events portrayed in Figure 27.2?
A) during Times C and D
B) during Times A and C
C) during Times B and C
D) during Times A and B
E) during Times B and D
Answer: A
50. Figure depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA). Use Figure to answer the following question.
Which question, arising from the results depicted in Figure 27.2, is most interesting from a genetic perspective, and has the greatest potential to increase our knowledge base?
A) If reciprocal crossing over could occur even if the piece of donated Hfr DNA is identical to the homologous portion of the recipient's chromosome, what prevents this from occurring?
B) What forces are generally responsible for disrupting the sex pilus?
C) How is it that a recipient cell does not necessarily become an Hfr cell as the result of conjugation with an Hfr cell?
D) What makes a cell an Hfr cell?
Answer: A
51) The data were collected from the heterocysts of a nitrogen-fixing cyanobacterium inhabiting equatorial ponds.
Study the following graph and choose the most likely explanation for the shape of the curve.
A) Enough O₂ enters heterocysts during hours of peak photosynthesis to have a somewhat-inhibitory effect on nitrogen fixation.
B) Light-dependent reaction rates must be highest between 1800 hours and 0600 hours.
C) Atmospheric N₂ levels increase at night because plants are no longer metabolizing this gas, so they are not absorbing this gas through their stomata.
D) Heterocyst walls become less permeable to N₂ influx during darkness.
E) The amount of fixed nitrogen that is dissolved in the pond water in which the cyanobacteria are growing peaks at the close of the photosynthetic day (1800 hours).
Answer: A
52) Consider the thermoacidophile, Sulfolobus acidocaldarius.
Which of the following graphs most accurately depicts the expected temperature and pH profiles of its enzymes? (Note: The horizontal axes of these graphs are double, with pH above and temperature below.)
A. A
B. B
C. C
D. D
Answer: A
53. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
This bacterium's ability to survive in a human who is taking penicillin pills may be due to the presence of
1. penicillin-resistance genes
2. a secretory system that removes penicillin from the cell
3. a gram-positive cell wall
4. a gram-negative cell wall
5. an endospore
A) 1 or 5
B) 2 or 3
C) 4 or 5
D) 2, 3, or 5
E) 2, 4, or 5
Answer: D
54. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
Adherence to the intestinal lining by this bacterium is due to its possession of
A) fimbriae.
B) pili.
C) a capsule.
D) a flagellum.
E) a cell wall with an outer lipopolysaccharide membrane.
Answer: C
55. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
What should be true of the cell wall of this bacterium?
A) Its innermost layer is composed of a phospholipid bilayer.
B) After it has been subjected to Gram staining, the cell should remain purple.
C) It has an outer membrane of lipopolysaccharide.
D) It is mostly composed of a complex, cross-linked polysaccharide.
E) Two of the responses above are correct.
Answer: C
56. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
Some of the proteins that allow this bacterium to swim are related (in an evolutionary sense) to proteins that
A) attach to the single chromosome.
B) act as restriction enzymes.
C) synthesize peptidoglycan for the cell wall.
D) move penicillin out of the cell.
E) comprise its ribosomes.
Answer: D
57. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
In which feature(s) should one be able to locate a complete chromosome of this bacterium?
1. nucleolus
2. prophage
3. endospore
4. nucleoid
A) 4 only
B) 1 and 3
C) 2 and 3
D) 3 and 4
E) 2, 3, and 4
Answer: D
58. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
The cell also lacks F factors and F plasmids. Upon its death, this bacterium should be able to participate in
A) conjugation.
B) transduction.
C) transformation.
D) Three of the responses above are correct.
E) Two of the responses above are correct.
Answer: C
59. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
This bacterium derives nutrition by digesting human intestinal contents (in other words, food). Thus, this bacterium should be an
A) aerobic chemoheterotroph.
B) aerobic chemoautotroph.
C) anaerobic chemoheterotroph.
D) anaerobic chemoautotroph.
Answer: C
60. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
This bacterium derives nutrition by digesting human intestinal contents (in other words, food). Humans lacking this bacterium have no measurable reproductive advantage or disadvantage relative to humans who harbor this bacterium. Consequently, the bacterium can be properly described as which of the following?
1. symbiont
2. endosymbiont
3. mutualist
4. commensal
A) 4 only
B) 1 and 2
C) 1 and 4
D) 2 and 3
E) 2 and 4
Answer: C
61. Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O₂ reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂. Consider the colonial aquatic cyanobacterium, Anabaena, whose heterocytes are described as having "…a thickened cell wall that restricts entry of O₂ produced by neighboring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates."
Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?
1. couple them with photosystem II (the photosystem that splits water molecules)
2. package them in membranes that are impermeable to all gases
3. be obligate anaerobes
4. be strict aerobes
5. package these enzymes in specialized cells or compartments that inhibit oxygen entry
A) 1 and 4
B) 2 and 4
C) 2 and 5
D) 3 and 4
E) 3 and 5
Answer: E
62. Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O₂ reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂. Consider the colonial aquatic cyanobacterium, Anabaena, whose heterocytes are described as having "…a thickened cell wall that restricts entry of O₂ produced by neighboring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates."
Which two questions below arise from a careful reading of this quotation, and are most important for understanding how N₂ enters heterocysts, and how O₂ is kept out of heterocysts?
- If carbohydrates can enter the heterocysts from neighboring cells via the "intracellular connections," how is it that O₂ doesn't also enter via this route?
- If the cell walls of Anabaena's photosynthetic cells are permeable to O₂ and CO₂, are they also permeable to N₂?
- If the nuclei of the photosynthetic cells contain the genes that code for nitrogen fixation, how can these cells fail to perform nitrogen fixation?
- If the nuclei of the heterocysts contain the genes that code for photosynthesis, how can these cells fail to perform photosynthesis?
- If the cell walls of Anabaena's heterocysts are permeable to N₂, how is it that N₂ doesn't diffuse out of the heterocysts before it can be fixed?
- If the thick cell walls of the heterocysts exclude entry of oxygen gas, how is it that they don't also exclude the entry of nitrogen gas?
A) 1 and 3
B) 1 and 6
C) 2 and 5
D) 3 and 4
E) 4 and 6
Answer: B
63. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Which two species should have much more phospholipid, in the form of bilayers, in their cytoplasms than most other bacteria?
A) species A and B
B) species A and C
C) species B and E
D) species C and D
E) species C and E
Answer: C
64. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Which species should be able to respond most readily to taxes (plural of taxis)?
A) species A
B) species B
C) species C
D) species D
E) species E
Answer: C
65. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
How many of these species probably have a cell wall that partly consists of an outer membrane of lipopolysaccharide?
A) only one species
B) two species
C) three species
D) four species
E) all five species
Answer: C
66. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Gram-variable prokaryotes are, sometimes, those without any peptidoglycan. Which two species are most likely to be archaeans?
A) species A and B
B) species A and C
C) species B and E
D) species C and D
E) species C and E
Answer: A
67. The following table depicts characteristics of five prokaryotic species (A—E). Use the
information in the table to answer the following question
.
Species D is pathogenic if it gains access to the human intestine. Which other species, if it coinhabited a human intestine along with species D, is most likely to result in a recombinant species that is both pathogenic and resistant to some antibiotics?
A) species A
B) species B
C) species C
D) species D
E) species E
Answer: C
68. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Which species might be able to include Hfr cells?
A) species A
B) species B
C) species C
D) species D
E) species E
Answer: D
69. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Which species is most self-sustaining in terms of obtaining nutrition in environments containing little fixed nitrogen or carbon?
A) species A
B) species B
C) species C
D) species D
E) species E
Answer: E
70. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Which two species might be expected to cooperate metabolically, perhaps forming a biofilm wherein one species surrounds cells of the other species?
A) species A and B
B) species A and C
C) species B and E
D) species C and D
E) species C and E
Answer: A
71. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Which species is most likely to be found both in sewage treatment plants and in the guts of cattle?
A) species A
B) species B
C) species C
D) species D
E) species E
Answer: B
72. The following table depicts characteristics of five prokaryotic species (A—E). Use the information in the table to answer the following question.
Which species is probably an important contributor to the base of aquatic food chains as a primary producer?
A) species A
B) species B
C) species C
D) species D
E) species E
Answer: E
73) Genetic variation in bacterial populations cannot result from
A) transduction.
B) transformation
C) conjugation
D) mutation.
E) meiosis.
Answer: E
74) Photoautotrophs use
A) light as an energy source and CO₂ as a carbon source.
B) light as an energy source and methane as a carbon source.
C) N₂ as an energy source and CO₂ as a carbon source.
D) CO₂ as both an energy source and a carbon source.
E) H₂S as an energy source and CO₂ as a carbon source.
Answer: A
75) Which of the following statements is not true?
A) Archaea and bacteria have different membrane lipids.
B) Both archaea and bacteria generally lack membrane-enclosed organelles.
C) The cell walls of archaea lack peptidoglycan.
D) Only bacteria have histones associated with DNA.
E) Only some archaea use CO₂ to oxidize H₂, releasing methane.
Answer: D
76) Which of the following involves metabolic cooperation among prokaryotic cells?
A) binary fission
B) endospore formation
C) endotoxin release
D) biofilms
E) photoautotrophy
Answer: D
77) Bacteria perform each of the following ecological roles. Which role typically does not involve a symbiosis?
A) skin commensalist
B) decomposer
C) aggregates with methane-consuming archaea
D) gut mutualist
E) pathogen
Answer: B
78) Plantlike photosynthesis that releases O₂ occurs in
A) cyanobacteria.
B) chlamydias.
C) archaea.
D) actinomycetes.
E) chemoautotrophic bacteria.
Answer: A
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MONERA
1. Air kaldu dalam tabung reaksi tertutup rapat, dipanaskan pada suhu 600C. Setelah dibiarkan selama satu minggu, ternyata timbul bakteri, bakteri tersebut berasal dari … .
A. air kaldu
B. spora
C. udara
D. daging
E. benda mati
2. Bakteri yang dapat mengikat N2 dari udara untuk membantu kesuburan tanah adalah … .
A. Mikrobacter & Escherchia
B. Azotobacter & Escherchia
C. Mycobacterium & Clostridium
D. Clastridium & Rhyzobium
E. Mycobacterium & Azotobacter
3. Bakteri patogen ini menyebabkan penyakit tertentu, yaitu … .
A. Trieponema pallidium penyebab penyakit tipus
B. Diplococcus pneumoniac penyebab penyakit disentri
C. Vibrio comma penyebab penyakit kolera
D. Clostridium gonorrhoeae penyebab penyakit sipilis
E. Pasteurella pestis penyebab penyakit kusta / lepra
4. Persamaan antara bakteri dan alga biru (Cyanophyta) antara lain ialah bahwa kedua duanya .
A. membentuk hifa
B. inti tak berdinding
C. mengandung fikosianin
D. hidup berkoloni
E. hidup autotrof
5. Peranan Cyanophyta dalam ekosistem antara lain sebagai pioner sebab … .
A. sebagai sumber makanan bagi organisme
B. dapat hidup di tempat yang tidak menguntungkan
C. dapat hidup di tempat yang gersang
D. dapat mengubah lingkungan sehingga organisme lain dapat hidup
E. merupakan tumbuhan kecil yang berhijau daun
6. Penyakit berbahaya yang disebabkan oleh bakteri vibrion adalah … .
A. tifus
B. kolera
C. disentri
D. radang tenggorokan
E. radang paru-paru
7. Bakteri yang dapat hidup dan berkembang biak pada medium yang mengandung zat-zat anorganik serta dapat mengoksidasi senyawa amoniak dan menghasilkan energi adalah … .
A. Clostiridium
B. Mycobacterium
C. Nitrosococus
D. Azotobacter
E. Neisseria
8. Makhluk hidup yang dapat mengurai sampah organik yang berasal dari tumbuhan mati dan bangkai ialah:
A. bakteri dan jamur
B. bakteri dan ganggang
C. ganggang dan rayap
D. ganggang dan cacing tanah
E. cacing tanah dan ulat
9. Bakteri yang berbentuk seperti koma dan membentuk bulu cambuk disebut:
A. basilus
B. kokus
C. spiril
D. vibrion
E. streptokokus
10. Penyakit berbahaya yang disebabkan oleh bakteri vibrion adalah … .
A. tifus
B. kolera
C. disentri
D. radang tenggorokan
E. radang paru-paru
11. Perkembangbiakan secara aseksual yang terjadi pada ganggang hijau-biru berlangsung melalui:
A. spora, pembelahan biner, konyugasi
B. heterocyst, spora dan fragmentasi
C. pembelahan biner, spora, hormogonium
D. arthroposa, konyugasi, hormogonium
E. fragmentasi, heterocyst, isogami
12. Bakteri kemoautotrof dapat mensintesis CO2 menjadi makanan dengan adanya … .
A. proses fisika
B. proses kimia
C. proses respirasi
D. bantuan matahari
E. tenaganya sendiri
13. Bakteri nitrogen yang menguraikan senyawa nitrat menjadi amonia adalah … .
A. Nitrobacter
B. Nitrosococcus
C. Clostiridium botolimum
D. Clostiridium perfiranges
E. Clostiridium desulfucaris
14. Bakteri Rhizobium yang dapat bersimbiosis dengan tanaman polong-polongan bermanfaat karena:
A. menghaluskan partikel-partikel tanah
B. memfiksasi nitrogen bebas menjadi nitrat yang digunakan untuk pertumbuhan tanaman inangnya
C. memecah senyawa anorganik menjadi senyawa organik
D. memfiksasi nitrat menjadi nitrogem bebas
E. memecah senyawa organik menjadi senyawa anorganik
15. Pembentukan asam cuka oleh bakteri-bakteri asam cuka disebabkan oleh pengaruh:
A. karbondioksida
B. oksigen
C. alkohol
D. asam
E. basa
16. Bakteri denitrifikasi tumbuh subur di tanah yang:
A. gembur, penuh bahan organik
B. liat, penuh bahan organik
C. gembur, penuh bahan organik
D. liat, penuh bahan anorganik
E. liat, gembur, penuh bahan anorganik
17. Bakteri yang dapat hidup dan berkembang biak pada medium yang mengandung zat-zat anorganik serta dapat mengoksidasi senyawa amoniak dan menghasilkan energi adalah … .
A. Clostiridium
B. Mycobacterium
C. Nitrosococus
D. Azotobacter
E. Neisseria
18. Peranan ganggang hijau-biru dalam ekosistem antara lain sebagai vegetasi perintis, sebab:
A. sebagai sumber makanan bagi makhluk hidup
B. dapat hidup di tempat yang tidak menguntungkan
C. dapat hidup di tempat kering
D. dapat mengubah lingkungan sehingga organisme lain dapat hidup
E. merupakan tumbuhan kecil yang mempunyai pigmen hijau-biru
19. Pigmen yang dikandung ganggang hijau-biru adalah … .
A. fikosianin
B. fikobilin
C. fikoeritrin
D. antosianin
E. sitokrom
20. Ganggang hijau-biru yang hidup dalam organisme lain disebut … .
A. sporofil
B. saprofit
C. parasit
D. endofit
E. ektofit
21. Perhatikan macam-macam penyakit di bawah ini:
1. Tipus
2. Trachom
3. Kolera
4. Rabies
5. Sipilis
6. Demam berdarah
Penyakit yang disebabkan oleh bakteri adalah …
A. 1 – 2 – 3
B. 2 – 3 – 4
C. 3 – 4 – 5
D. 1 – 3 – 5
E. 1 – 5 – 6
22. Bakteri yang berperanan untuk pembuatan nata de coco adalah … .
A. Lactobacilus casei
B. Acetobacter xylinum
C. Streptococcus griceus
D. Pseudomonas cocovenenan
E. Borditella pertusie
23. Jenis Alga biru yang hidup bersimbiosis dengan tumbuhan tinggi dan sangat menguntungkan karena mengikat N2 bebas dari udara adalah … .
A. Rhyzobium
B. Anabaena
C. Rivularia
D. Nostoc
E. Azotobacter
24. Bakteri dan ganggang biru dimasukkan ke dalam golongan Monera, atas dasar … .
A. ukuran selnya
B. selaput intinya
C. cara reproduksinya
D. bentuk organella selnya
E. struktur dinding selnya
25. Beberapa bukti yang menunjukkan bahwa sel eukariot berasal dari sel prokariot adalah ...
a. berdasarkan bentuk-bentuk fosil yang ditemukan
b. berdasarkan bukti-bukti yang ditunjukkan oleh teori Infolding dan endosimbiotik
c. sel eukariot masih memiliki komponen sel prokariot
d. sel eukariot memiliki habitat yang sama dengan prokariot
e. ukuran sel eukariot yang lebih besar dibandingkan prokariot
26. Berapa lama waktu yang dibutuhkan oleh sel prokaryot berevolusi menjadi sel eukariot?
a. tidak ada batasan waktu
b. 1 antara 1 - 1,5 milyar tahun
c. setara dengan masa hidup sel prokariot
d. Sepanjang waktu sel membelah
e. tergantung pada habitat. prokariot yang hidup di daerah ekstrim lebih cepat berubah menjadi eukariot
27. Pernyataan tentang teori Infolding adalah ...
a. proses pembentukkan membran nukleus pada sel prokariot
b. proses penggandaan kromosom sirkuler pada sel eukariot
c. proses invaginasi dari membran sel untuk membentuk organel-organel sel pada sel prokaryot
d. proses pembentukkan flagel dan filli untuk mempercepat gerakan sel
e. Penebalan dinding sel prokariot dalam upaya mengatasi lingkungan yang buruk
28. Dua jenis organel sel yang terbentuk menurut teori endosymbiotik adalah ...
a. ribosom dan mesosom
b. kloroplast dan sitoplasma
c. retikulum endoplasma dan badan golgi
d. sentrosom dan mitokondria
e. kloroplas dan mitokondria
29. Reproduksi seksual bakteri yang dilakukan dengan cara pertukaran materi genetik dengan bantuan virus disebut ...
a. pembelahan biner
b. transeksual
c. transduksi
d. konjugasi
e. transformasi
30. Fungsi filli saat pada reproduksi konjugasi?
a. alat untuk melekat pada bakteri lain
b. sebagai benang penghubung untuk menukarkan materi genetik
c. alat untuk mengeluarkan materi genetik
d. alat untuk membentuk subtansi genetika baru
e. alat untuk mentransfer materi genetik
31. Bahan dasar pembentuk struktur dinding sel bakteri adalah ...
a. lipoprotein
b. semipermeabel
c. lendir
d. peptidoglikan
e. lemak
32. Struktur organel sel dibawah ini yang tidak pernah dijumpai pada sel prokaryot adalah ...
a. plasmid
b. mitokondria
c. ribosom
d. dinding sel
e. membran plasma
33. Makhluk hidup yang termasuk prokariot dan memiliki jumlah paling besar adalah ...
a. Eubakteri
b. archaebacteria
c. cyanobacteria
d. protozoa
e. ganggang
34. organisme yang termasuk kelompok prokaryot adalah ...
a. protozoa, jamur dan alga
b. protozoa, alga biru dan bakteri
c. protozoa, virus, dan monera
d. protozoa, virus dan cyanobacteria
e. Eubacteria, cyanobacteria dan archaebacteria
35. Prokaryot yang hidup di daerah ekstrim adalah ...
a. Archaebacteria
b. eubacteria
c. cyanobacteria
d. klorophyta
e. protozoa
36. Prokaryot yang mengambil bahan anorganik dan merubahnya menjadi bahan organik melalui proses fotosintesis adalah ...
a. Archaebacteria
b. eubacteria
c. cyanobacteria
d. klorophyta
e. protozoa
37. Tempat hidup dari archaebacteria adalah ...
a. kawah gunung berapi, laut mati dan usus besar hewan herbivora
b. tanah gambut, kawah gunung merapi, dan usus besar hewan karnovora
c. kawah gunung berapi, laut mati dan usus besar hewan karnivora
d. tanah gambut, laut mati, dan usus besar hewan herbivora
e. tanah gambut, laut mati dan usus besar hewan karnivora
38. Kelompok organisme yang dikenal dengan nama bakteri sejati adalah ...
a. Archaebacteria
b. eubacteria
c. cyanobacteria
d. klorophyta
e. protozoa
39. Struktur sel yang tidak dimiliki oleh organisme prokariot adalah ...
a. dinding sel
b. membran sel
c. membran plasma
d. membran inti
e. selaput semipermeabel
40. Nama bakteri yang memiliki banyak flagel pada salah satu ujung tubuhnya adalah ...
a. peritriks
b. amfitriks
c. Lopotriks
d. monotriks
e. ditriks
41. Bakteri yang menyebabkan penyakit thypus adalah bakteri yang mempunyai flagela bertipe
a. peritriks
b. amfitriks
c. Lopotriks
d. monotriks
e. ditriks
42. Beberapa fungsi organel prokariot
1. membentuk jembatan konjugasi
2. tempat sintesis protein
3. alat untuk mengapung
4. alat gerak
5. alat tukar-menukar materi genetik
Fungsi dari filli adalah ...
a. 1 - 2 - 3
b. 3 - 4 - 5
c. 1 - 3 - 5
d. 2 - 4 - 4
e. 2 - 3 - 5
43. Bakteri yang menyebabkan penyakit Radang paru paru atau Pnemonia adalah koloni bakteri yang membentuk.
a. streptococcus
b. diplococcus
c. sarcina
d. staphylococcus
e. tetracoccus
44. Racun eksotoksi adalah ...
a. racun yang dihasilkan oleh bakteri gram negatif
b. racun yang dihasilkan oleh bakteri gram positif
c. racun yang dihasilkan oleh bakteri yang sudah mati
d. racun yang dihasilkan oleh archaebacteria
e. racun yang dihasilkan oleh cyanobacteria
45. Berdasarkan letak flagelnya, Bentuk bakteri Escherisia coli adalah ...
a. peritriks
b. lopotriks
c. amfitriks
d. monotriks
e. ditriks
46. Dinding sel archaebacteria berbeda dengan eubacteria, yaitu dinding sel archaebacteria ...
a. terbuat dari selulosa
b. memiliki peptidoglikan yang tebal
c. memiliki peptidoglikan yang tipis
d. memiliki bentuk berlapis-lapis
e. mengandung ribosom
47. Berdasarkan cara respirasinya, Archaebacteria termasuk dalam kelompok ...
a. aerob
b. aerob obligat
c. anaerob
d. anaerob obligat
e. anaerob fakultatif
48. Tempat hidup dari bakteri metanogen adalah ...
a. kawah gunung berapi
b. laut mati
c. tanah gambut
d. usus besar hewan herbivora
e. tempat lembab
49. nama jenis archaebacteria yang dapat hidup di lingkungan yang sangat asin adalah ...
a. halofit
b. termofil
c. metanogen
d. acidofil
e. termoacidofil
50. bakteri gram negatif adalah ...
a. bakteri yang memiliki lapisan peptidoglikan tipis dan dengan pewarnaan gram menghasilkan warna ungu
b. bakteri yang memiliki lapisan peptidoglikan tipis dan dengan pewarnaan gram menghasilkan warna biru
c. bakteri yang memiliki lapisan peptidoglikan tebal dan dengan pewarnaann gram menghasilkan warna biru
d. bakteri yang memiliki lapisan peptidoglikan tebal dan dengan pewarnaan gram menghasilkan warna ungu
e. bakteri yang tidak memiliki lapisan peptidoglikan pada dinding selnya, tapi hidup di daerah yang ekstrim
51. dapatkah bakteri gram positif diberantas dengan menggunakan antibiotika?
a. tidak bisa karena lapisan peptidoglikannya tipis
b. tidak bisa karena peptidoglikannya tebal
c. bisa, karena lapisan peptidoglikannya tipis
d. bisa, karena lapisan peptidoglikannya tebal
e. bisa karena lapisan peptidoglikan berubah-ubah ketebalannya
52. kelompok Cyanobacterium atau alga biru yang berbentuk benang adalah ...
a. Nostoc
b. rivularia
c. anabaena
d. gleocapsa
e. oscilatoria
53. Cyanobacteria merupakan prokariot yang dapat melakukan fotosintesis. jenis pigmen yang dimiliki utama yang dimiliki organisme ini adalah ...
a. pigmen hijau-biru
b. pigmen hijau kuning
c. pigmen biru kuning
d. pigmen biru merah
e. pigmen biru jingga
54. Pada cyanobacteria terdapat struktur yang memiliki kemampuan untuk memfiksasi nitrogen yaitu ...
a. heterokist
b. hormogonium
c. sporokiste
d. spiroseta
e. nematokist
55. Escherisia coli termasuk kelompok bakteri enterik sebab ...
a. hidup di dalam tubuh makhluk hidup
b. merupakan bakteri anaerob fakultatif
c. menghasilkan racun atau toksik
d. mampu mengubah bahan organik menjadi anorganik
e. mengubah selolusa menjadi metanaDETAIL
Ciri-Ciri Bakteri
Dalam klasifikasi terbaru, bakteri dibagi menjadi 2 bagian kelompok besar yaitu Archeobacteria dan Eubacteria diantara keduanya memiliki ciri khusus, dan secara umum bakteri mempunyai ciri-ciri sebagai berikut:
1. Tubuh Uniseluler (bersel satu)
2. Prokariotik atau tidak memiliki membran inti sel.
3. Berdiameter antara 0,5 – 1 mikron dengan panjang 1 – 20 mikron, sehingga hanya dapat dilihat menggunakan mikroskop.
4. Hidup secara soliter atau berkoloni.
5. Mempunyai dinding sel.
6. Kosmopolit yaitu habitatnya meliputi daerah yang luas dan di berbagai ekosistem.
7. Umumnya tidak berklorofil meskipun beberapa jenis bakteri memiliki pigmen seperti klorofil sehingga mampu berfotosintesis dan bersifat autotrof.
B. Struktur Bakteri
Struktur bakteri dibagi menjadi 2 yaitu :
1. Struktur Dasar Bakteri
Struktur dasar bakteri adalah struktur yang dimiliki oleh hampir semua jenis bakteri diantaranya :
a. Bahan Inti, merupakan pusat pengendali aktivitas sel yang berisi DNA, bakteri memiliki rantai tunggal DNA yang disebut nukleoid.
b. Sitoplasma, yaitu cairan sel dimana didalamnya terdapat asam nulkeat, protein, karbohidrat, lemak dan lain lain.
c. Ribosom, adalah butiran-butiran organel yang tersebar dalam sitoplasma yang mengandung molekul RNA sebagai tempat sintesis protein.
d. Granula penyimpanan, adalah tempat menyimpan cadangan makanan yang dibutuhkan.
e. Membran plasma (selaput sitoplasma), bersifat selektif permeabel (hanya dapat dilalui molekul atau zat tertentu). Tersusun atas protein dan fosfolipid, membran plasma memiliki fungsi antara lain sebagai alat transpor elekron dan proton, pengatur pengangkutan senyawa dan tempat terbentuknya mesosom.
f. Dinding Sel, berfungsi sebagai pelindung dan pemberi bentuk tubuh sel bakteri, tersusun atas peptidoglikan yaitu gabungan protein dan polisakarida. Peptidoglikan membagi bakteri menjadi bakteri gram positif (peptidoglikan tebal) contohnya neisseria gonorrhea, treponema pallidum. dan bakteri gram negatif (peptidoglikan tipis) contohnya, escherichia coli, staphylococcus aureus.
2. Struktur tambahan bakteri
Struktur tambahan bakteri biasanya hanya dimiliki oleh jenis bakteri tertentu atau bisa dikatakan tidak dimiliki oleh jenis bakteri tertentu, struktur tambahan bakteri terdiri atas :
a. Flagela (flagellum), yaitu alat gerak bakteri yang biasanya terdapat pada bakteri yang hidup di habitat air, beberapa tipe bakteri berdasarkan letak flagelanya yaitu:
1) Atrik, yaitu bakteri yang tidak berflagela
2) Monotrik, bakteri yang memiliki satu flagela.
3) Amfitrik, dua buah flagela di kedua ujung tubuhnya.
4) Lofotrik, terdapat segerombol flagela di salah satu ujung tubuh.
5) Peritrik, flagelanya terdapat di seluruh permukaan tubuh.
b. Kapsul atau lapisan lendir, bila lapisannya tebal disebut kapsul dan bila lapisan tipis disebut lapisan lendir, kapsul tersusun atas polisakarida dan air, memiliki fungsi antara lain:
1) Alat melekat bakteri pada sel inang
2) Mencegah kekeringan pada sel bakteri
3) Alat perlindungan dan sumber makanan bagi bakteri.
c. Pilus dan fimbria, yaitu struktur berbentuk rambut halus yang menonjol dari dinding sel, mirip flagelum tetapi lebih pendek dan terdapat pada bakteri negatif sedangkan fimbria adalah struktur sejenis pilus tetapi lebih pendek.
d. Klorosom, yaitu struktur yang berada di bawah membran plasma, klorosom mengandung pigmen klorofil dan pigmen lainnya yang berperan dalam proses fotosintesis, klorosom hanya terdapat pada bakteri yang mampu melakukan fotosintesis.
e. Vakuola gas, berguna agar bakteri dapat mengapung di permukaan air untuk memperoleh cahaya, vakuola gas hanya terdapat pada bakteri di air yang mampu melakukan fotosintesis.
f. Endospora, merupakan bentuk bakteri ketika sedang istirahat, endospora ditemui di beberapa jenis bakteri gram positif dan terbentuk di dalam sel bakteri jika kondisi lingkungan tidak menguntungkan bagi kehidupan bakteri. Endospora tersusun atas sitoplasma, DNA, dan ribosom. Dinding endospora yang tebal tahan terhadap kondisi ekstrim seperti kekeringan, radiasi cahaya, suhu, maupun zat kimia. Jika kondisi lingkungan memungkinkan maka endospora akan tumbuh menjadi sel bakteri baru.
C. Bentuk Bakteri
Adanya dinding sel pada bakteri menyebabkan bakteri mempunyai bentuk yang bersifat tetap. Bentuk bakteri terdiri dari :
1. Coccus (kokus/bola)
a. Monococcus, yaitu bentuk kokus/bola tunggal, contoh: Neisseria gonorrhoeae
b. Diplococcus, yaitu bentuk bola berpasangan, contoh : Diplococcus pneumoniae.
c. Tetracoccus, yaitu empat sel bakteri berdempetan membentuk segi empat.
d. Streptococcus, bentuk bola berantai, contoh: Azotobacter, Bacillus anthracis.
e. Staphylococcus, berbentuk bola bergerombol seperti buah anggur, contoh: Staphylococcus aureus.
f. Sarcina, bentuk bola berdempetan membentuk kubus, contoh : Sarcina sp.
2. Bacillus (basil/batang)
a. Monobacillus, bentuk batang tunggal, contoh Escherichia coli, Lactobacillus.
b. Diplobacillus, bentuk batang berpasangan
c. Streptobacillus, bentuk batang berkoloni berbentuk rantai, contoh : Azotobacter, streptobacillus moniliformis.
3. Spirillum (spiral)
a. Spirillum, bentuk spiral bergelombang, contoh spirillum minor.
b. Spirochaeta, yaitu bentuk sel seperti sekrup atau kumparan, contoh : treponema pallidum.
4. Vibrio (koma), yaitu bentuk sel bakteri seperti tanda baca koma atau kurang dari setengah lingkaran.
D. Klasifikasi Bakteri
Bakteri merupakan organisme yang dapat kita temui hidup di segala habitat dan dengan jumlah yang sangat banyak dibandingkan dengan makhluk hidup lain. Bakteri secara umum dapat dibagi menjadi dua kelompok besar yaitu Archaebacteria dan Eubacteria, selain itu bakteri juga dapat diklasifikasikan berdasarkan sumber nutrisi dan kebutuhan oksigennya.
1. Klasifikasi bakteri secara umum, bakteri terbagi menjadi :
a. Archaebacteria
Berasal dari bahasa yunani : archaio yang berarti kuno.Archaebacteria adalah kelompok bakteri primitif, archaebacteria dianggap sebagai nenek moyang dari bakteri yang ada sekarang archaebacteria bersifat prokariotik, dapat hidup di habitat yang ekstrim seperti daerah berkadar garam tinggi maupun di tempat bersuhu panas, memiliki ciri khusus seperti :
- Dinding selnya tidak mengandung peptidoglikan
- Membran selnya mengandung lipida berikatan eter.
- Ribosomnya mengandung beberapa jenis RNA polimerase
Archaebacteria terbagi menjadi beberapa kelompok, yaitu :
1) Bakteri Metanogen/metanogenik
Bakteri jenis ini mendapatkan makanan dari sisa-sisa pembusukan bahan organik, dimana proses pembusukan tersebut menghasilkan gas metana (CH4).
Bakteri metanogen yang bersifat anaerobik dan kemosintetik ini hidup di habitat rawa dan lingkungan yang berkadar oksigen rendah, bakteri yang hidup di laut mendapatkan makanan dari bahan organik yang jatuh ke laut.
2) Bakteri Halofil/halofilik
Berasal dari kata halo : garam, dan philos : suka, bakteri halofil yaitu bakteri yang dapat hidup di lingkungan yang berkadar garam tinggi , bakteri ini mampu melakukan fotosintesis dengan menggunakan klorofil bacteriorhadopsin (ungu), contoh : Halobacterium sp.
3) Bakteri Termoasidofil/termoasidofilik
Bakteri ini hidup di lingkungan ekstrim yang memiliki suhu tinggi serta tingkat keasaman tinggi, contohnya seperti kawah gunung vulkanik dari gunung berapi dan mata air bersulfur.
b. Eubacteria
Eubacteria memiliki ciri khusus yang membedakannya dari archaebacteria diantaranya :
- Adanya peptidoglikan pada dinding selnya
- Membran plasmanya mengandung lipida berikatan ester
- Ribosom mengandung satu jenis RNA polimerase
Eubacteria dibagi menjadi 5 kelompok yaitu :
1) Bakteri Gram Positif
Beberapa bakteri gram positif dapat berfotosintesis dan ada yang bersifat kemoheterotrof, bakteri ini dapat membentuk endospora ketika keadaan lingkungan kurang menguntungkan. Contoh : Bacillus, Clostridium, Mycobacterium tubercolosis dan Mycoplasma gallisepticum.
2) Cyanobacteria
Cyanobacteria dahulu dikenal dengan ganggang hijau biru, hidup soliter maupun berkoloni. Cyanobacteria ada yang bersel satu dan juga bersel banyak, tidak mempunyai membran inti dan tidak memiliki banyak organela serta tidak memiliki alat gerak. Cyanobacteria berukuran antara 1 - 60 µm.
Pada cyanobacteria terdapat pigmen klorofil, karoten, dan pigmen tambahan berupa fikosianin (biru), dan fikoeritrin (merah). Contoh cyanobacteria adalah Anabaena, Oscillatoria rubescens, nostoc, anabaena azollae, azolla pinnata.
3) Proteobacteria
Proteobacteria bersifat autotrof dan terdapat klorofil pada membran sel, protebacteria dapat dibedakan menjadi tiga kelompok yaitu :
a) Bakteri ungu kemoautotrof
b) Proteobacteria kemoautotrof
c) Proteobacteria kemoheterotrof
Bakteri ungu terdapat pada endapan danau, kolam, dan lumpur, contoh Chromatium. Proteobacteria kemoautotrof hidup bebas atau bersimbiosis dengan makhluk hidup lain. Sedangkan proteobacteria kemoheterotrof hidup di saluran pencernaan contoh Escherichia coli, salmonella.
4) Spirochetes
Spirochetes sebagian hidup bebas dan sebagian hidup sebagai parasit dan menjadi penyebab penyakit, spirochetes merupakan bakteri gram negatif yang bersifat kemoheterotrof dan berukuran antara 5 – 250 µm dan berbentuk spiral. Pada spirochetes terdapat filamen aksial berupa serabut disepanjang tubuhnya dan berfungsi untuk gerakan berputar. Contoh: Treponema pallidum, leptospira interrogans.
5) Chlamydias
Chlamydias merupakan kelompok bakteri dengan ukuran paling kecil yaitu antara 0,2 – 1,5 µm dengan bentuk tidak beraturan. Chlamydias hanya dapat hidup sebagai parasit dalam sel-sel makhluk hidup lain. Contoh: chlamydias trachomatis.
2. Klasifikasi bakteri menurut kebutuhan oksigennya, yaitu :
a. Bakteri Aerob, yaitu bakteri yang memerlukan oksigen untuk memperoleh energi, contoh Nitrosomonas, nitrosococcus.
b. Bakteri Anaerob, yaitu bakteri yang tidak membutuhkan oksigen untuk memperoleh energi, energi diperoleh antara lain dengan cara fermentasi. Contoh Esherichia coli, lactobacillus.
3. Klasifikasi bakteri menurut sumber nutrisinya, yaitu :
a. Bakteri Autotrof, yaitu bakteri yang dapat mengubah bahan anorganik menjadi bahan organik sebagai sumber makanan, bakteri autotrof dibagi menjadi dua kelompok yaitu:
1) Bakteri fotoautotrof (fototrof) adalah jenis bakteri yang menggunakan cahaya matahari sebagai sumber energinya.
2) Bakteri kemoautotrof, adalah bakteri yang memperoleh energi dengan cara mengoksidasi senyawa-senyawa kimia anorganik. Contohnya Nitrosomonas, nitrobacter.
b. Bakteri Heterotrof, adalah bakteri yang memproleh energi dari bahan-bahan organik, dibagi menjadi :
1) Bakteri heterotrof yang hidup sebagai parasit, yaitu jenis bakteri yang mendapatkan makanan dari organisme lain yang menjadi inangnya, contoh Mycobacterium tubercolosis.
2) Bakteri heterotrof yang hidup sebagai saprofit, yaitu bakteri yang mendapatkan makanan dengan cara merombak bahan organik menjadi bahan anorganik melalui proses fermentasi, bakteri ini biasanya apatogen. Contoh : Escherichia coli, clostridium sporageus.
E. Reproduksi Bakteri
1. Reproduksi Aseksual
Pada umumnya bakteri melakukan reproduksi atau berkembang biak secara aseksual dengan cara pembelahan biner yang biasanya setiap sel bakteri membelah menjadi dua. Proses pembelahan biner dimulai dari replikasi DNA, pemisahan sitoplasma kemudian diikuti dengan terbentuknya dinding pemisah, dan selanjutnya terbentuklah dua sel bakteri.
2. Reproduksi Seksual
Reproduksi bakteri secara seksual yaitu dengan pertukaran materi genetik dari satu bakteri ke bakteri lain, disebut juga rekombinasi genetik atau paraseksual. Rekombinasi bakteri menghasilkan dua sel bakteri yang terjadi dengan tiga cara yaitu :
a. Transformasi : yaitu proses pemindahan sedikit materi genetik (DNA) ke dalam sel bakteri lain.
b. Transduksi : pemindahan materi genetik dari satu sel bakteri ke bakteri lain dengan perantaraan virus (bakteriofage)
c. Konyugasi : perpindahan materi genetik yang berupa plasmid langsung melalui kontak sel dengan membentuk struktur seperti jembatan dengan sel bakteri didekatnya.
F. Contoh Peranan Bakteri.
Dalam kehidupan manusia bakteri mempunyai peranan yang menguntungkan maupun merugikan.
1. Contoh peranan bakteri yang menguntungkan
a. Bidang Pertanian :
1) Bakteri nitrit (nitrosomonas dan nitrococcus) dan bakteri nitrat (nitrobacter) adalah bakteri yang membantu proses pembentukan senyawa nitrat dalam tanah
2) Azetobacter, clostrodium pasteurianum, rodospirillium rubrum dan rhizobium mampu mengikat N2 bebas dari udara.
b. Bidang Industri :
1) Lactobacillus casei, berperan dalam fermentasi keju dan yoghurt.
2) Acetobacter xylinum, menghasilkan asam cuka dan natan de coco
3) Streptococcus lactis, berperan dalam fermentasi keju dan mentega.
4) Propionibacterium berperan dalam pembuatan asam propionat.
5) Methanomonas methanica berperan dalam pembuatan gas bio.
6) Clostridium acebutylicum menghasilkan aseton dan butanol.
c. Bidang Farmasi :
1) Streptococcus griseus, menghasilkan antibiotik streptomisin
2) Streptomyces venezuelae, menghasilkan antibiotik kloromisetin
3) Streptomyces aureofaciens, menghasilkan antibiotik aureomisin
4) Streptomyces rimosus, menghasilkan antibiotik tetrasiklin
5) Pseudomonas denitrificans, menghasilkan vitamin B12
6) Bacillus brevis, menghasilkan antibiotik tirotrisin.
7) Bacillus subtilis, menghasilkan antibiotik basitrasin.
8) Bacillus polymyxa, menghasilkan polymixin.
d. Bidang lain :
1) Escherichia coli, pembusukan sisa makanan di usus serta membantu pembentukan vitamin K.
2. Contoh berbagai bakteri yang merugikan.
Beberapa bakteri menyebabkan penyakit pada manusia, hewan dan tumbuhan.
a. Penyebab penyakit pada manusia, antara lain :
1) Mycobacterium tubercolosis, penyebab penyakit TBC
2) Mycobacterium leprae, penyebab penyakit lepra.
3) Clostrodium tetani, penyebab penyakit tetanus.
4) Salmonella typhi, dapat menyebabkan penyakit tifus.
5) Vibrio cholerae, penyebab penyakit kolera.
6) Shigella disentriae, penyebab penyakit disentri.
7) Pasteurella pestis, penyebab panyakit pes.
8) Diplococcus pneumonia, menyebabkan radang paru-paru.
9) Treponema pallidium,menyebabkan penyakit sifilis.
10) Neisseria gonorrheaea, menyebabkan penyakit gonoro.
11) Leptospira sp., dapat menyebabkan penyakit leptospirosis.
b. Penyebab penyakit pada hewan dan tumbuhan, antara lain :
1) Bacillus anthracis, menyebabkan penyakit antraks pada sapi, kerbau, dan domba.
2) Brucella abortus, menyebabkan penyakit bruselosis pada sapi.
3) Pseudomonas solanacearum, penyebab penyakit pada tomat, terung, dan tembakau.
4) Agrobacterium tumafaciens, penyebab penyakit tumor pada tumbuhan.
5) Xanthomonas citri, penyebab penyakit kanker pada batang jeruk.
6) Erwinia tracheiphila, menyebabkan busuk pada daun labu.
7) Psedomonas cattleyae, menyebabkan busuk pada daun anggrek.
c. Menyebabkan rusaknya makanan, yaitu :
1) Clostridium botulinum, menyebabkan makanan kaleng rusak.
2) Pseudomonas cocovenenans, menyebabkan rusaknya tempe.
3) Leuconostoc mesentroides, menyebabkan makanan basi.
G. Faktor-faktor yang mempengaruhi pertumbuhan bakteri.
Faktor-faktor yang mempengaruhi pertumbuhan bakteri atau kondisi pertumbuhan optimum dari bakteri yaitu :
1. Suhu/temperatur, pada umumnya bakteri dapat tumbuh baik pada suhu antara 250C sampai 350C.
2. Derajat keasaman atau pH
3. Konsentrasi garam
4. Sumber nutrisi, dimana tersedia sumber nutrisi untuk pertumbuhan bakteri
5. Kelembapan, dimana bakteri umumnya hidup di lingkungan yang memiliki kelembapan tinggi karena sangat menguntungkan untuk pertumbuhan bakteri.
6. Cahaya, umumnya cahaya dapat merusak sel bakteri karena ionisasi pada komponen sel yang menghambat pertumbuhan bakteri.
7. Zat kimia, antibiotik, logam berat dan senyawa-senyawa kimia tertentu dapat menghambat bahkan mematikan bakteri.
Adapun faktor-faktor diatas bervariasi menurut spesies bakterinya
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