Question 1

Which step in the nitrogen cycle is primarily carried out by decomposer bacteria, and what is the main product of this process?

Accepted Answer

Ammonification; produces $$NH_4$$^+$$

Question 2

Which bacterium is known for its ability to inject DNA into plant cells, thereby causing the plant to produce nutrients for the bacterium?

Accepted Answer

Agrobacterium

Question 3

A researcher observes a bacterium that can replicate its stalked cell and undergoes a unique cell cycle. Which bacterium is most likely being observed?

Accepted Answer

Caulobacter

Question 4

Which of the following bacteria is a parasite of Gram-negative bacteria and grows in the periplasm?

Accepted Answer

Bdellovibrio

Question 5

Streptomyces is important in medicine because it can produce which of the following as secondary metabolites?

Accepted Answer

Antibiotics

Question 6

Which bacterium is capable of producing fluorescent light in response to crowded growth conditions?

Accepted Answer

Photobacterium

Question 7

Deinococcus radiodurans is notable for its ability to survive in which extreme environment, and what is the main reason for this resilience?

Accepted Answer

Nuclear reactors; robust DNA repair mechanisms and shielded cell wall

Question 8

Which bacterium undergoes a 'snapping division' as part of its cell cycle?

Accepted Answer

Corynebacterium diphtheriae

Question 9

Match the fermentation type with the correct bacterium and its industrial importance: Which bacterium is used in the production of Swiss cheese and is associated with propionic acid fermentation?

Accepted Answer

Propionibacterium; Swiss cheese

Question 10

Which of the following is NOT a strategy used by nitrogen-fixing bacteria to protect nitrogenase from oxygen damage?

Accepted Answer

Producing antibiotics

Question 11

A plant root nodule is found to have a low oxygen environment. Which molecule is most likely responsible for maintaining this condition to protect nitrogenase?

Accepted Answer

Leghemoglobin

Question 12

Which process in the nitrogen cycle converts $$NH_4$$^+$$ to NO_2$^-$$, and which group of bacteria is responsible for this transformation?

Accepted Answer

Nitrification; nitrifying bacteria

Question 13

Sulfate-reducing bacteria use which electron donors and acceptors, and what is a notable environmental effect of their metabolism?

Accepted Answer

Organic electron donors and $$SO_4$$^{2-}$$ as electron acceptor; produces black goo and causes odor

Question 14

Which bacteria are known for their versatile metabolism, allowing them to survive in diverse environments?

Accepted Answer

Pseudomonas

Question 15

Which of the following is a correct description of the role of denitrifying bacteria in the nitrogen cycle?

Accepted Answer

Convert $$NO_3$$^-$$ to N_2$ gas, returning nitrogen to the atmosphere

Question 16

Which fermentation type is associated with lactic acid bacteria, and what is a common industrial product of this process?

Accepted Answer

Lactic acid fermentation; yogurt

Question 17

A soil sample is found to contain bacteria that form cysts and increase their respiration rate to limit oxygen concentration. What is the primary function of these adaptations?

Accepted Answer

To protect nitrogenase from oxygen damage during nitrogen fixation

Question 18

Which bacterium is used in the production of buttermilk and is associated with lactic acid fermentation?

Accepted Answer

Lactic acid bacteria

Question 19

Which process is responsible for converting atmospheric $$N_2$$ into a biologically usable form, and which enzyme is central to this process?

Accepted Answer

Nitrogen fixation; nitrogenase

Question 20

Which bacteria help plants by forming root nodules and maintaining a low oxygen environment for nitrogen fixation?

Accepted Answer

Rhizobium

Microbial Roles in the Nitrogen Cycle and Unique Bacterial Characteristics

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