Q: A bacterium with a generation time of 30 minutes is inoculated into a culture medium. If you start with 1 cell, how many cells will there be after 3 hours, assuming exponential growth and no cell death? Use the formula $$N = N_0$ \times 2^n$$, where $$n is $$the number of generations.

$$N = 1 \times 2^6$ = 64$$ cells

Question 1

Which of the following best describes the process of binary fission in prokaryotic cells?

Accepted Answer

A single cell divides into two genetically identical daughter cells, each receiving a chromosome and sufficient cellular constituents.

Question 2

A bacterium with a generation time of 30 minutes is inoculated into a culture medium. If you start with 1 cell, how many cells will there be after 3 hours, assuming exponential growth and no cell death? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

$$N = 1 	imes 2^6$ = 64$$ cells

Question 3

Which of the following is a key adaptation that allows psychrophilic bacteria to thrive at low temperatures?

Accepted Answer

Increased proportion of unsaturated and shorter-chain fatty acids in their membranes

Question 4

Which of the following statements about macronutrients and micronutrients in bacterial cells is correct?

Accepted Answer

Macronutrients are required in large amounts and include elements like C, N, O, H, P, and S.

Question 5

A bacterium isolated from a soda lake grows optimally at pH 10. Which adaptation is most likely present in this organism?

Accepted Answer

It maintains a neutral internal pH by exchanging sodium ions for external protons.

Question 6

Which of the following best explains why oxygen can be toxic to some microorganisms?

Accepted Answer

Oxygen exposure leads to the formation of reactive oxygen species such as superoxide anion ($$O_2$$^-$$), hydrogen peroxide (H_2O_2$), and hydroxyl radical (OH$$\cdot$$).

Question 7

Which of the following is a correct pairing of microbial group and its oxygen requirement?

Accepted Answer

Obligate anaerobe – cannot grow in the presence of $$O_2$$

Question 8

Which of the following is a real-world example of a biofilm and its impact?

Accepted Answer

Dental plaque leading to cavities and gum disease

Question 9

A bacterium is found to require high concentrations of NaCl (15-30%) for growth and cannot grow at lower concentrations. This organism is best classified as a:

Accepted Answer

Extreme halophile

Question 10

Which of the following best describes the role of compatible solutes in microbial cells?

Accepted Answer

They help maintain positive water balance by accumulating in the cytoplasm without inhibiting cellular processes.

Question 11

Which adaptation is most likely found in hyperthermophilic Archaea to maintain membrane stability at high temperatures?

Accepted Answer

Membranes composed of lipid monolayers with ether bonds between isoprene units and glycerol phosphate

Question 12

Which of the following is a correct description of a chemolithoautotroph?

Accepted Answer

Uses inorganic chemicals as an energy source and $$CO_2 as a $$carbon source

Question 13

A patient with a prosthetic joint develops a persistent infection that is resistant to antibiotics and immune clearance. Which microbial growth form is most likely responsible?

Accepted Answer

Biofilm

Question 14

Which of the following is a function of iron (Fe) as a micronutrient in microbial cells?

Accepted Answer

Acts as a cofactor in cellular respiration and oxidation-reduction reactions

Question 15

Which of the following best explains why microbial culture media often contain buffers?

Accepted Answer

To maintain a constant pH, ensuring macromolecule stability and optimal microbial growth

Question 16

Which of the following is a correct statement about the nutritional diversity of prokaryotes?

Accepted Answer

Some prokaryotes can use inorganic chemicals as energy sources, while others require organic compounds.

Question 17

Which of the following is a plausible reason why biofilms are more resistant to antibiotics than planktonic cells?

Accepted Answer

The extracellular polysaccharide matrix impedes the penetration of antibiotics.

Question 18

Which of the following best describes the main difference between budding and binary fission in bacteria?

Accepted Answer

Budding produces daughter cells of unequal size, while binary fission produces two equal daughter cells.

Question 19

A microbe isolated from maple syrup is able to grow at a water activity ($$a_w) of 0.90. $$Which group does it most likely belong to?

Accepted Answer

Gram-positive cocci such as Staphylococcus (halotolerant bacteria)

Microbial Metabolism and Growth: Environmental and Nutritional Factors Affecting Bacterial Growth

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