Chapter 6 Tortora Fall 2024 (2)

Question 1

What are biofilms?

Answer 1

Microbial communities that form slime or hydrogels

Biofilms share nutrients and are sheltered from harmful factors.

Question 2

What is culture medium?

Answer 2

Nutrients prepared for microbial growth

Question 3

Define sterile.

Answer 3

No living microbes

Question 4

What is inoculum?

Answer 4

Introduction of microbes into medium

Question 5

What is a culture?

Answer 5

Microbes growing in/on culture medium

Question 6

What is agar?

Answer 6

Complex polysaccharide used as solidifying agent for culture media

Question 7

At what temperature does agar liquefy?

Answer 7

100°C

Question 8

At what temperature does agar solidify?

Answer 8

~40°C

Question 9

What are chemically defined media?

Answer 9

Media where exact chemical composition is known

Question 10

How is generation time calculated?

Answer 10

60 min × hours / Number of generations

Question 11

What is complex media?

Answer 11

Extracts and digests of yeasts, meat, or plants

Question 12

What is the purpose of differential media?

Answer 12

To distinguish colonies of different microbes

Question 13

What are capnophiles?

Answer 13

Microbes that require high CO2 conditions

Question 14

What do reducing media contain?

Answer 14

Chemicals like thioglycolate or oxyrase that combine O2

Question 15

What is the optimum growth temperature for most bacteria?

Answer 15

Between pH 6.5 and 7.5

Question 16

What are psychrotrophs?

Answer 16

Microbes that grow between 0°C and 20–30°C

Question 17

What pH range do molds and yeasts typically grow in?

Answer 17

Between pH 5 and 6

Question 18

What is plasmolysis?

Answer 18

The process caused by hypertonic environments

Question 19

What are extreme halophiles?

Answer 19

Microbes that require high osmotic pressure

Question 20

What is a pure culture?

Answer 20

Contains only one species or strain

Question 21

What is a colony-forming unit (CFU)?

Answer 21

A population of cells arising from a single cell or spore

Question 22

What method is used to isolate pure cultures?

Answer 22

The streak plate method

Question 23

What is a Coulter counter?

Answer 23

An electronic device that counts cells by measuring resistance changes

Question 24

What does turbidity estimation measure?

Answer 24

Bacterial numbers based on light scattering

Question 25

What is the enrichment culture method?

Answer 25

Encourages growth of a desired microbe

Question 26

What does the most probable number (MPN) method involve?

Answer 26

Counting positive tubes to estimate bacterial concentration

Question 27

What is the pour plate method?

Answer 27

Inoculating an empty plate with melted nutrient agar and swirling to mix

Question 28

What is the spread plate method?

Answer 28

Inoculating a plate containing solid medium and spreading inoculum over the surface

Question 29

What are direct methods for measuring microbial growth?

Answer 29

* Plate counts * Filtration * MPN * Direct microscopic count * Coulter Counter

Question 30

What are indirect methods for measuring microbial growth?

Answer 30

* Turbidity * Dry weight

Question 31

What are the phases of microbial growth?

Answer 31

* Lag Phase * Log Phase * Stationary Phase * Death Phase

Question 32

What is binary fission?

Answer 32

A method of reproduction in prokaryotes

Question 33

What is deep-freezing?

Answer 33

Preservation method at –50° to –95°C

Question 34

What is lyophilization?

Answer 34

Freeze-drying process at –54° to –72°C