Module 4: Environmental Conditions for Bacterial Growth

Question 1

What are the 2 main environmental conditions that must be appropriate for growth?

Answer 1

Temperature, atmosphere, and nutritional requirements

Question 2

Define minimum, optimum, and maximum temperature limits

Answer 2

Minimum - lowest temperature at which a bacteria will grow
Optimal - temperature giving best growth
Maximum - highest temperature at which a bacteria will grow

Question 3

Define psychrophilic

Answer 3

Cold loving

15-20 degrees celsius

Question 4

Define mesophilic

Answer 4

Middle loving

25-40 degrees celsius

Question 5

Define thermophilic

Answer 5

Heat loving

45-50 degrees celsius

Question 6

What temperature are most laboratory incubators set at? Why?

Answer 6

35 degrees celsius
Because pathogens will grow at 35 and if the temperature fluctuates up to 37 it will still grow
If it starts at 37 and goes up to 39 the bacteria may die

Question 7

Define capnophilic

Answer 7

Carbon dioxide loving

Question 8

What amount of carbon dioxide do capnophilic organisms require? How much is in ambient air?

Answer 8

3-10%, usually 3-6%

0.03% in ambient air

Question 9

How can a capnophilic environment be provided to bacteria?

Answer 9

Candle extinction jar - light candle, close lid, oxygen reduced, CO2 at about 2.5%
Chemical generation/GasPak
Carbon dioxide incubator

Question 10

How does a candle extinction jar work?

Answer 10

Light candle, close lid

Oxygen is reduced, CO2 goes up to about 2.5%

Question 11

How does chemical generation/GasPak work?

Answer 11

Cut corner of packet, add water

Citric acid and bicarbonate release CO2

Question 12

What is an obligate aerobe?

Answer 12

Bacteria that requires oxygen for growth

Question 13

What is an obligate anaerobe?

Answer 13

Bacteria that requires absence of oxygen

Growth is inhibited or bacteria is killed by oxygen

Question 14

What is a facultative anaerobe?

Answer 14

Can grow anaerobically

Grow BETTER in oxygen

Question 15

What is a microaerophilic organism?

Answer 15

Bacteria that requires oxygen for growth but at a lower concentration

Question 16

A wound swab is inoculated onto BAPs and incubated in O2, CO2 and ANO2
BAP O2 = 4+ growth of white colonies
BAP CO2 = no growth
BAP ANO2 = 2+ growth of white colonies, 4+ growth of gray colonies

a. classify the white colonies
b. classify the gray colonies

Answer 16

a. facultative anaerobe

b. obligate anerobe

Question 17

Bacterial growth is present throughout a tube of semi-solid medium. What type of bacteria is present?

Answer 17

Facultative anaerobe

Question 18

Bacterial growth is present only at the top of a tube of semi-solid medium. What type of bacteria is present?

Answer 18

Obligate aerobe

Question 19

Bacterial growth is present only in the middle of a tube of semi-solid medium. What type of bacteria is present?

Answer 19

Microaerophilic

Question 20

Bacterial growth is present only at the bottom of a tube of semi-solid medium. What type of bacteria is present?

Answer 20

Obligate anaerobe

Question 21

The candle extinction jar

a. provides growth conditions for anaerobic bacteria
b. allows growth of capnophilic bacteria
c. provides a moist atmosphere
d. a, b, and c
e. a and c
f. b and c

Answer 21

f. b and c (allows growth of capnophilic bacteria, provides a moist atmosphere)

Question 22

Bacteria with an optimum temperature above 45 degrees are called

a. mesophilic
b. psychrophilic
c. thermophilic

Answer 22

c. thermophilic

Question 23

Microbiology laboratory incubators should be maintained at

a. 34 degrees
b. 35 degrees
c. 36 degrees
d. 37 degrees

Answer 23

b. 35 degrees