Microbial Growth

Question 1

physical requirements that affect growth

Answer 1

temperature and pH

Question 2

chemical requirements that affect growth

Answer 2

C, N, S, P, O; trace elements, organic growth factors

Question 3

psychrophiles

Answer 3

0-20C

Question 4

mesophiles

Answer 4

15-45C

Question 5

thermophiles

Answer 5

40-80C

Question 6

hyperthermophiles

Answer 6

65-121

Question 7

extreme/obligate halophiles

Answer 7

require high osmotic pressure

Question 8

facultative halophiles

Answer 8

tolerate high osmotic pressure

Question 9

obligate aerobe

Answer 9

requires oxygen for growth

Question 10

facultative anaerobe

Answer 10

can grow in the presence of oxygen, can grow by fermentation or anaerobic respiration in the absence of oxygen

Question 11

obligate anaerobe

Answer 11

cannot grow in the presence of O

Question 12

aerobic respiration

Answer 12

the final electron acceptor in the ETC is oxygen

Question 13

culture medium

Answer 13

nutrients prepared for microbial growth

Question 14

sterile

Answer 14

no living microbes

Question 15

inoculum

Answer 15

introduction of microbes into medium

Question 16

culture

Answer 16

microbes growing in/on culture medium

Question 17

chemically defined media

Answer 17

exact chemical composition is known

Question 18

complex media

Answer 18

extracts and digests of meat, yeasts, or plants

Question 19

capnophiles

Answer 19

organisms that require high CO2 conditions (similar to intestinal tract)

Question 20

differential media

Answer 20

makes it easier to distinguish colonies of different microbes

Question 21

selective media

Answer 21

suppress unwanted microbes and encourage desired microbes

Question 22

generation time

Answer 22

the time it takes for a population to double in number

Question 23

Mathematical formula to calculate number of microbes (binary fission):

Answer 23

Nt = No x 2^n

Where Nt is the final cell number, No is the original cell number, and n is the number of generations

Question 24

generation time of E coli:

Answer 24

20-30 minutes

Question 25

batch culture

Answer 25

a liquid media within a closed system

Question 26

Exponential growth never lasts __________.

Answer 26

indefinitely

Question 27

chemostat

Answer 27

ensures logarithmic growth by constantly adding and removing equal amounts of culture media

Question 28

What is similar to a chemostat?

Answer 28

human gastrointestinal tract

Question 29

3 Ways to measure microbial growth?

Answer 29

Direct count, Viable cell count/plate count, Mass measurements (turbidity)

Question 30

direct count

Answer 30

microbes can be counted directly by placing dilutions on a special microscope slide, called a Petroff-Hausser counting chamber

Question 31

Mass measurement (turbidity)

Answer 31

light scattering is proportional to cell mass

Question 32

Turbidimetric measurements (4)

Answer 32

1. optical density 2. light scattering ability of microbial cultures 3. depends on organism and culture conditions 4. should be calibrated for the above criteria