Question 1

Which classification best describes an organism that uses carbon dioxide as its carbon source, sunlight as its energy source, and water as its electron source?

Accepted Answer

Photoautotroph

Question 2

A bacterium is classified as an obligate anaerobe. Which of the following best explains why it cannot survive in the presence of oxygen?

Accepted Answer

It lacks enzymes to detoxify reactive oxygen species such as superoxide ($$\mathrm{O_2$^-}) $$and hydrogen peroxide ($$\mathrm{H_2O_2}).$$

Question 3

Nitrogen-fixing bacteria play a crucial role in the nitrogen cycle. Which process do they perform?

Accepted Answer

They convert atmospheric nitrogen ($$\mathrm{N_2$}) $$into ammonia ($$\mathrm{NH_3$}).$$

Question 4

Why is nitrogen essential for microbial growth?

Accepted Answer

It is a key component of nucleic acids and proteins.

Question 5

A culture medium lacks magnesium and iron. What is the most likely effect on bacterial growth?

Accepted Answer

Growth will be limited because these are essential trace elements.

Question 6

A psychrophile is most likely to be found in which environment?

Accepted Answer

Arctic sea ice, where temperatures are below $$20^\circ \mathrm{C}.$$

Question 7

Which type of microorganism thrives at a pH of 2 and is commonly found in acidic hot springs?

Accepted Answer

Acidophile

Question 8

A bacterium placed in a hypertonic solution will most likely experience which phenomenon?

Accepted Answer

Plasmolysis, due to water leaving the cell.

Question 9

Barophiles are microorganisms that thrive under which conditions?

Accepted Answer

High pressure, such as deep-sea environments.

Question 10

Which relationship describes two microorganisms living together, where both benefit from the association?

Accepted Answer

Mutualistic (a type of symbiotic relationship)

Question 11

Biofilms are problematic in healthcare settings because:

Accepted Answer

They increase resistance to antibiotics and disinfectants.

Question 12

Quorum sensing in bacteria is best described as:

Accepted Answer

A process where bacteria communicate to coordinate gene expression based on population density.

Question 13

Which term refers to the initial sample of microorganisms introduced into a culture medium?

Accepted Answer

Inoculum

Question 14

Why is it important to obtain a pure culture when analyzing clinical specimens?

Accepted Answer

To ensure accurate identification and susceptibility testing of the pathogen.

Question 15

The streak plate technique is used primarily to:

Accepted Answer

Isolate individual colonies from a mixed sample.

Question 16

Which type of culture medium is designed to distinguish between different types of bacteria based on their biochemical properties?

Accepted Answer

Differential medium

Question 17

If a bacterial population starts with 100 cells and undergoes 5 generations of binary fission, how many cells will be present? (Use $$2^n$$ where $$n is $$the number of generations)

Accepted Answer

$$100 	imes 2^5$ = 3200$$ cells

Question 18

Which phase of microbial growth is characterized by rapid cell division and exponential increase in population size?

Accepted Answer

Log (exponential) phase

Question 19

Which method is considered a direct measurement of microbial growth?

Accepted Answer

Counting colony-forming units (CFUs) on an agar plate.

Question 20

A hospital technician is transporting a patient sample. Which precaution is most important to prevent contamination and infection?

Accepted Answer

Using universal precautions, such as gloves and sealed containers.

Microbial Nutrition and Growth: Chapter 6 Study Guide

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