Question 1

Which of the following statements best explains why phylogenetic diversity and ecological/functional diversity do not always correspond in bacteria?

Accepted Answer

Horizontal gene transfer and convergent evolution allow unrelated bacteria to perform similar metabolic functions.

Question 2

Which bacterial group is exclusively responsible for oxygenic photosynthesis in aquatic environments?

Accepted Answer

Cyanobacteria

Question 3

What is the primary function of heterocysts in filamentous Cyanobacteria?

Accepted Answer

Nitrogen fixation in an anaerobic environment

Question 4

Which pigment combination is characteristic of Cyanobacteria, enabling them to perform oxygenic photosynthesis?

Accepted Answer

Chlorophyll a and phycobilins

Question 5

Purple sulfur bacteria, such as Chromatium, are typically found in which environment and utilize which electron donor for photosynthesis?

Accepted Answer

Anaerobic, sulfide-rich environments, using H2S as electron donor

Question 6

Which metabolic pathway is used by green sulfur bacteria (e.g., Chlorobium) to fix CO2?

Accepted Answer

Reverse Citric Acid Cycle

Question 7

Which equation correctly represents the energy-generating reaction of ammonia-oxidizing bacteria?

Accepted Answer

$$\mathrm{NH_3$ + O_2$ \rightarrow NH_2OH \rightarrow $$HNO_2$$}$$

Question 8

Which of the following best describes the ecological role of methanotrophs?

Accepted Answer

They reduce atmospheric methane by oxidizing CH4 to CO2.

Question 9

Which enzyme is unique to methanotrophs and is essential for methane oxidation?

Accepted Answer

Methane monooxygenase (MMO)

Question 10

Which process is carried out by dissimilative sulfate-reducing bacteria, such as Desulfovibrio?

Accepted Answer

Reduction of sulfate to hydrogen sulfide under anaerobic conditions

Question 11

A Winogradsky column is set up with mud, cellulose, and calcium sulfate. After several weeks, purple sulfur bacteria are observed. Which metabolic process are these bacteria most likely performing?

Accepted Answer

Anoxygenic photosynthesis using H2S as electron donor

Question 12

Which of the following best describes the relationship between methylotrophs and methanotrophs?

Accepted Answer

Methanotrophs are a subset of methylotrophs that specifically use methane as a carbon and energy source.

Question 13

Which of the following bacteria is known for forming symbiotic relationships with legumes and fixing atmospheric nitrogen?

Accepted Answer

Rhizobium

Question 14

Which of the following equations represents the process of denitrification carried out by some Pseudomonas species?

Accepted Answer

$$\mathrm{NO_3$^- \rightarrow NO_2$^- \rightarrow N_2O \rightarrow NO \rightarrow N_2$}$$

Question 15

Which of the following is a unique structural adaptation found in some Cyanobacteria that allows them to fix nitrogen in the presence of oxygenic photosynthesis?

Accepted Answer

Heterocysts

Question 16

Which of the following best describes the ecological role of Gallionella in bogs and springs?

Accepted Answer

Chemoautotrophic oxidation of Fe2+ to Fe3+, forming Fe(OH)3 deposits

Question 17

Which metabolic process is performed by Nitrospira and Nitrobacter, and what is the key enzyme involved?

Accepted Answer

Oxidation of nitrite to nitrate; nitrite oxidoreductase

Question 18

Which of the following best describes the life cycle of Myxobacteria?

Accepted Answer

Individual cells aggregate to form a multicellular fruiting body and produce myxospores under starvation conditions.

Question 19

Which of the following is a key ecological consequence of denitrification by bacteria in soils and water?

Accepted Answer

Loss of bioavailable nitrogen to the atmosphere as N2 gas

Question 20

Which of the following best describes the metabolic versatility of Proteobacteria?

Accepted Answer

They exhibit a wide range of metabolic types, including photoautotrophy, chemoautotrophy, and heterotrophy.

Ecological Diversity of Bacteria: Metabolic Strategies and Functional Roles Ch 15

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