Question 1

Which of the following statements best describes the ubiquity of bacteria?

Accepted Answer

Bacteria are found everywhere on the planet and can survive in harsh environments.

Question 2

What is the main structural difference between Gram-positive and Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.

Question 3

Which bacterial shape is correctly matched with its description?

Accepted Answer

Spirillum: spiral-shaped

Question 4

During which phase of the microbial growth curve do bacteria rapidly increase in number?

Accepted Answer

Logarithmic (exponential) phase

Question 5

Which type of bacteria would you expect to thrive at temperatures above 80°C?

Accepted Answer

Hyperthermophiles

Question 6

What is the function of an axial filament in spirochetes?

Accepted Answer

It enables motility by causing the cell to twist and move.

Question 7

Which property is NOT characteristic of fungi?

Accepted Answer

Fungi are photosynthetic.

Question 8

Why is Sabouraud’s agar commonly used for culturing fungi?

Accepted Answer

It is acidic, which favors fungal growth and inhibits many bacteria.

Question 9

Which of the following best describes a pure culture?

Accepted Answer

A culture containing only one type of bacteria.

Question 10

What is the main goal of the streak plate method in microbiology?

Accepted Answer

To obtain isolated colonies from a mixed culture.

Question 11

Which type of culture media contains ingredients with unknown exact composition?

Accepted Answer

Complex media

Question 12

Mannitol salt agar is selective for which group of bacteria?

Accepted Answer

Gram-positive bacteria

Question 13

Which component in MacConkey agar inhibits the growth of Gram-positive bacteria?

Accepted Answer

Crystal violet and bile salts

Question 14

Which of the following is a differential medium and what does it detect?

Accepted Answer

Mannitol salt agar; detects mannitol fermentation

Question 15

A bacterium that acquires carbon from organic matter and energy from the breakdown of organic compounds is classified as:

Accepted Answer

Chemoheterotroph

Question 16

Which equation best represents the exponential growth of bacteria during the log phase?

Accepted Answer

$$N_t = N_0$ e$$^{r t}$$

Question 17

Which of the following is a correct statement about molds?

Accepted Answer

Molds are made up of intertwining filaments called hyphae.

Question 18

Which type of bacteria would be most likely to contaminate refrigerated foods?

Accepted Answer

Psychrophiles

Question 19

Which of the following is NOT a requirement for preparing a culture medium?

Accepted Answer

Antibiotic resistance genes

Question 20

A student streaks a plate and observes both yellow and red colonies on Mannitol salt agar. What does this indicate?

Accepted Answer

Yellow colonies are mannitol fermenters; red colonies are non-fermenters.

Microbiology Lab Study Guide: Culture Media, Pure Culture Technique, Ubiquity of Bacteria, and The Fungi

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