Lecture 9

Question 1

generation time is dependent on..

Answer 1

growth medium and incubation conditions

Question 2

exponential growth

Answer 2

growth of microbial pop. in which cells double

Question 3

generation time of exponentially growing pop…

Answer 3

duration of exponential growth divided by number of generations during period of growth

Question 4

batch culture

Answer 4

a closed-system microbial culture of fixed volume; conditions are constantly changing and it’s impossible to independently control growth rate and yield

Question 5

Typical growth curve for population of cells grown in a closed system is characterized by which four phases?

Answer 5

• lag
• exponential
• stationary
• death

Question 6

continuous culture

Answer 6

an open-system microbial culture of fixed volume

Question 7

chemostat

Answer 7

most common type of continuous culture device

Question 8

Both growth rate and population density of a continuous culture (chemostat) can be controlled..

Answer 8

independently and simultaneously

Question 9

dilution rate

Answer 9

rate at which fresh medium is pumped in and spent medium is pumped out; this can control growth rate

Question 10

conc. of limiting nutrient

Answer 10

growth yield; can control conc. of microbes/ml = “cell density”

Question 11

At too high dilution rate..

Answer 11

organism is washed out

Question 12

AT too low dilution rate..

Answer 12

cells may die from starvation

Question 13

Increasing conc. of a limiting nutrient results in..

Answer 13

greater biomass, but same growth rate

Question 14

limitations of microscopic counts

Answer 14

• live or dead cells?
• small cells can be overlooked
• precision is difficult
• phase-contrast required if stain is not used
• low density hard to count
• motile cells need to be immobilized
• debris can be mistaken for cells

Question 15

flow cytometer

Answer 15

a second method for enumerating cells in liquid samples; uses case beams, fluorescent dyes, and electronic

Question 16

viable counts

Answer 16

measurement of living, reproducing populations

Question 17

two ways to perform plate counts?

Answer 17

• spread plate

- pour plate

Question 18

great plate anomaly

Answer 18

direct microscopic counts of natural samples reveal more organisms than those recoverable on plates

Question 19

spectrophotometry

Answer 19

• turbidity measurements

- indirect, rapid, useful measurement of growth

Question 20

spectrophotometry measurement is referred to as..

Answer 20

optical density

Question 21

conditions affecting growth

Answer 21

• temp
• pH
• osmolarity
• oxygen availability

Question 22

cardinal temp.

Answer 22

minimum, optimum, and max temo at which organisms grow

Question 23

temp. optimum of psychrophile

Answer 23

4*

Question 24

temp. optimum of mesophiles

Answer 24

39*

Question 25

temp. optimum of of hyperthermophiles

Answer 25

88* or 106*

Question 26

extremophiles

Answer 26

organisms that grow under very hot or very cold conditions

Question 27

psychrophiles

Answer 27

organisms with cold temp. optima; inhabit permanently cold environments

Question 28

psychrotolerant

Answer 28

-can grow at 0, but optima of 20-40*; more widely distributed than psychrophiles

Question 29

features that allow production of enzymes that function optimally in the cold

Answer 29

• more a-helices
• more polar, less hydrophobic amino acids
• fewer weak bonds
• decreased interactions between protein domains
• transport processes function optimally at low temp.
• modified cytoplasmic membranes (high unsaturated fatty acid content)

Question 30

Above ~65*….

Answer 30

only prokaryotic life forms exist

Question 31

thermophiles

Answer 31

organisms with growth temp. optima between 45-80

Question 32

hyperthermophiles

Answer 32

optima greater than 80*

Question 33

In hyperthermophiles in hot springs…

Answer 33

chemoorganotrophic and chemolitzotrophic species are present

Question 34

____ prokaryotic diversity at high temp.

Answer 34

high

Question 35

Each microbe has a pH range ______ pH units within which growth is possible.

Answer 35

2-3pH units

Question 36

Most natural environments are…

Answer 36

pH 3-9

Question 37

neutrophiles

Answer 37

grow optimally at pH 5.5-7.9

Question 38

acidophiles

Answer 38

grow optimally at low pH (<5.5)

Question 39

obligate acidophiles

Answer 39

destroyed at neutral pH

Question 40

alkaliphiles

Answer 40

grow best at high pH (>/8)

Question 41

water activity

Answer 41

ratio of vapour pressure of air in equil. with a substance or soln to the vapour pressure of pure water

Question 42

water activity varies from..

Answer 42

zero (no free water) to one (pure water)

Question 43

osmosis

Answer 43

water diffuses from high to low conc.

Question 44

Typically, the cytoplasm has a _____ solute conc. than surrounding environment.

Answer 44

higher

Question 45

aerobes

Answer 45

require oxygen

Question 46

microaerophiles

Answer 46

can use oxygen when present

Question 47

facultative organisms

Answer 47

can live with or without oxygen

Question 48

anaerobes

Answer 48

cannot respire oxygen

Question 49

aerotolerant anaerobes

Answer 49

tolerate oxygen and grow in its presence but cannot respire

Question 50

obligate anaerobes

Answer 50

inhibited or killed by oxygen

Question 51

controlling microbial growth

Answer 51

-heat
-radiation and filtration
0chemical controls