Microbiology Ch. 6/7

The addition of which of the following to a culture medium will neutralize acids?

• Buffers

• Sugars

• Carbon

• Heat

• pH

Which enzyme catalyzes the reaction: H2O2 + 2H+ --> 2H2O?

• Superoxide dismutase

• Oxidase

• Catalase

• Peroxidase

Most bacteria grow best at pH

• 9.

• 5.

• 1.

• 7.

• 14.

Which of the following pairs is mismatched?

• Mesophile - growth at 25°C

• Psychrotroph - growth at 0°C

• Hyperthermophiles - growth at 100°C

• Thermophile - growth at 37°C

• Psychrophile - growth at 15°C

Salts and sugars work to preserve foods by creating a

• Hypotonic environment.

• Lower osmotic pressure.

• Depletion of nutrients.

• Lower pH.

• Hypertonic environment.

Three cells with generation times of 30 minutes are inoculated into a culture medium. How many cells are there after 5 hours?

• 48

• 1024

• 243

• 3 x 2^10

• 16

Patients with indwelling catheters are susceptible to infections because

• Biofilms develop on catheters.

• Injected solutions are contaminated.

• Their immune systems are weakened.

• Bacteria cause infections.

• Infections can be transmitted from other people.

Which of the following is an example of a metabolic activity that could be used to measure microbial growth?

• Glucose consumption

• Direct microscopic count

• MPN

• Turbidity

• Standard plate count

Which of the following is NOT a direct method to measure microbial growth?

• Metabolic activity

• Standard plate count

• MPN

• Direct microscopic count

• Filtration

A culture medium consisting of agar, human blood, and beef heart is a

• Reducing medium.

• Selective medium.

• Complex medium.

• Differential medium.

• Chemically defined medium.