Chapter 5

Question 1

Microbes have both the fastest and slowest

Answer 1

growth rates
• Some hot springs bacteria double in as little as 10 min
• Some deep-sea sediment microbes take as long as 100 years)

Question 2

What determines the differences in growth rate?

Answer 2

• Nutrition
• Temperature
• pH
• Osmolarity

Question 3

What are “normal” growth conditions?

Answer 3

sea level, 20-40C, neutral pH, salt concentration 0.9%, and many nutrients

Question 4

Fastest growth rate occurs

Answer 4

at temp where all proteins work most efficiently

• Rising temperatures cause enzymes or cell membrane to fail

Question 5

at colder temperatures

Answer 5

enzymatic processes become too sluggish and the cell membrane becomes too rigid

Question 6

Arrhenius equation

Answer 6

k=Ae^-Ea/RT. growth rate roughly doubles every 10C

Question 7

Mesophiles:

Answer 7

15-45C

Question 8

Psychrophiles (0-20C)

Answer 8

• Proteins are more flexible

* Require less energy (heat) to function

Question 9

Thermophiles (40-80C)

Answer 9

• Enzymes are more stable
• Chaperone
• Membranes are more rigid

Question 10

Barophiles or piezophiles

Answer 10

grow at high pressures

Question 11

Barotolerant

Answer 11

grow over 1-50 MPa but their growth falls off

Question 12

Water activity (aw)

Answer 12

is a measure of how much water is available for use

Question 13

Osmolarity

Answer 13

# of solute molecules in soln and inversely related to a(w)
• The more particles in a solution=greater osmolarity and the lower the water activity

Question 14

aquaporins

Answer 14

allow water to cross the membrane faster than by diffusion

• Help protect the cell from osmotic stress

Question 15

• Hypertonic

* Hypotonic

Answer 15

– external osmolarity is higher

– internal osmolarity is higher

Question 16

When in a hypertonic solution, bacteria

Answer 16

try to protect their internal water from leaving by importing more solutes (proline, potassium)

Question 17

Halophiles

Answer 17

• Require high salt (NaCl) concentrations to grow

Question 18

Neutralophiles

Answer 18

pH 5-8

Question 19

acidophiles

Answer 19

pH 0-5
• Often chemoautotrophs
• tetraether lipids

Question 20

Alkaliphiles

Answer 20

pH 9-11
• in soda lakes
• Use Na motive force and Na+/H+ antiporters

Question 21

Nutrient deprivation and starvation

Answer 21

• Growth rates slow
• stress responses
• Cells begin to make/store glycogen
• Programmed cell death – members of pop sacrifice themselves to save others – dying cells release nutrients for other cells

Question 22

sterilization

Answer 22

killing of all living organisms

Question 23

disinfection

Answer 23

killing pathogens from inanimate objects

Question 24

antisepsis

Answer 24

killing pathogens from the surface of living tissues

Question 25

sanitation

Answer 25

reducing microbial pop to safe levels

Question 26

Cells treated with antimicrobials die at a logarithmic rate

• D-value (decimal reduction time)-

Answer 26

time it takes the agent to kill 90% of population

Question 27

2 D-values

Answer 27

time to kill 99% of cells

Question 28

Physical agents that kill microbes

Answer 28

• Temperature
• Temperature + Pressure
• Irradiation
• Filtration
• Chemical agents

Question 29

temperature and time

Answer 29

LTLT (low temperature/long time): 63C for 30 min
• HTST (high temperature/short time): 72C for 15 seconds
• UHT (ultra high temperature): 150C for 3 seconds,
immediate cooling

Question 30

other methods

Answer 30

freezing, irradiation, filtration

Question 31

• Bacteriostatic

* Bacteriocidal

Answer 31

• inhibits growth

- kills cells