microbiology exam 2 chapter 4 pt 2

Question 1

How do microorganisms combat low water activity in their environment?

Answer 1

Microorganisms combat low water activity by:

Pumping inorganic ions from the environment into the cell.
Synthesizing or concentrating organic solutes.

Question 2

What are compatible solutes?

Answer 2

Compatible solutes are compounds used by cells to counteract low water activity in their surroundings, helping maintain cellular function in environments with low water availability.

Question 3

What is the role of oxygen in microbial growth?

Answer 3

Microorganisms use oxygen for aerobic respiration as a terminal electron acceptor.

Question 4

What is aerobic respiration in microorganisms?

Answer 4

It’s the process where oxygen is used in the electron transport chain to produce energy.

Question 5

What are strict (obligate) aerobes?

Answer 5

Organisms that can only grow in oxygen.

Question 6

what are microaerophiles?

Answer 6

Organisms that grow only at lower oxygen levels.

Question 7

What are strict (obligate) anaerobes?

Answer 7

Organisms that die in the presence of oxygen.

Question 8

What are aerotolerant anaerobes?

Answer 8

Organisms that grow in oxygen but use fermentation for energy.

Question 9

What are facultative anaerobes?

Answer 9

Organisms that can grow with or without oxygen, using both fermentation and respiration.

Question 10

How does a reducing agent like thioglycolate work in oxygen-removal?

Answer 10

It reacts with oxygen, allowing oxygen to only penetrate the top of the tube

Question 11

What is an anaerobe jar used for?

Answer 11

It removes O2 through a reaction catalyzed by palladium.

Question 12

How does an anaerobic chamber work?

Answer 12

Oxygen is removed by vacuum and replaced with N2 and CO2.

Question 13

What are capnophiles?

Answer 13

Microbes that require high CO2 conditions.

Question 14

How can CO2 conditions be created for culturing capnophiles?

Answer 14

Using a CO2 packet or candle jar.

Question 15

What is sterilization?

Answer 15

Killing of all living organisms.

Question 16

What does disinfection refer to?

Answer 16

Killing or removal of pathogens from inanimate objects.

Question 17

What is antisepsis?

Answer 17

Killing or removal of pathogens from the surface of living tissues.

Question 18

What does sanitation involve?

Answer 18

Reducing the microbial population to safe levels

Question 19

What is the D-value?

Answer 19

The D-value is the length of time it takes an agent or condition to kill 90% of the population

Question 19

How do microbes die?

Answer 19

Microbes die according to a negative exponential curve, where cell numbers are reduced in equal fractions at constant intervals.

Question 20

How does high temperature kill microbes?

Answer 20

High temperature denatures macromolecules.

Question 21

What is the effect of boiling water on microbes?

Answer 21

Boiling water (100°C) kills most cells but does not kill spores and thermophiles.

Question 22

How are spores and thermophiles typically killed?

Answer 22

Spores and thermophiles usually require a combination of high pressure and temperature, like in a steam autoclave (121°C at 15 psi for 20 minutes).

Question 23

t/f: Moist heat is more effective than dry heat.

Answer 23

true

Question 24

What is an autoclave and how does it kill microbes?

Answer 24

ealed device that uses steam under pressure. Allows temperature of water to get above 100ºC

Question 25

what kills microbes in autoclaving

Answer 25

it's not the pressure, but the high temperature, that kills the microbes

Question 26

What are the different methods of pasteurization and their temperatures?

Answer 26

LTLT (Low Temperature/Long Time): 63ºC for 30 minutes HTST (High Temperature/Short Time): 72ºC for 15 seconds

Question 27

What bacteria are killed by pasteurization?

Answer 27

Pasteurization kills most pathogenic bacteria, including Mycobacterium tuberculosis, Salmonella, and Listeria, but does not kill all microbes (e.g., spores) or some heat-resistant bacteria.

Question 28

How does cold temperature affect microbial growth?

Answer 28

Cold temperatures slow microbial growth and preserve strains, which is useful for storing cultures and food preservation.

Question 29

What are methods for long-term storage of cultures?

Answer 29

Placing solutions in glycerol at –70ºC Lyophilization or freeze-drying

Question 30

refrigeration temperatures are used for food preservation whats the temp range

Answer 30

4C-8C

Question 31

What is the function of micropore filters in filtration?

Answer 31

Micropore filters with pore sizes of 0.2 µm can remove microbial cells, but not viruses, from solutions.

Question 32

How can samples be processed through micropore filters?

Answer 32

Samples from 1 ml to several liters can be drawn through a membrane filter by vacuum or forced through it using a syringe.

Question 33

How can air be sterilized, and what is the role of HEPA filters?

Answer 33

Air can be sterilized by filtration using laminar flow biological safety cabinets that force air through HEPA filters. These filters remove >99.9% of airborne particulate material 0.3 μm in size or larger.

Question 34

What is the effect of ultraviolet (UV) light on microbes?

Answer 34

UV light sterilizes surfaces but has poor penetrating power.

Question 35

How do gamma rays, electron beams, and X-rays kill microbes?

Answer 35

These rays have high penetrating power and are used for sterilizing food and heat-sensitive items.

Question 36

What factors influence the efficacy of a chemical agent?

Answer 36

Presence of organic matter Types of organisms present Corrosiveness Stability, odor, and surface tension

Question 37

How are chemical agents evaluated for effectiveness?

Answer 37

Chemical agents are evaluated by in-use tests.

Question 38

What are some common commercial disinfectants and antiseptics?

Answer 38

Ethanol Iodine (Wescodyne, Betadine) Chlorine Ethylene oxide (gas sterilant)

Question 39

How do commercial disinfectants and antiseptics work?

Answer 39

They damage proteins, lipids, and/or DNA to reduce or eliminate microbial content.

Question 40

How can bacteria develop resistance to disinfectants?

Answer 40

Altering fatty acid synthesis proteins (targeted by triclosan) Producing multidrug efflux pumps Forming multispecies biofilms for collaborative protection

Question 41

What are antibiotics?

Answer 41

Chemical compounds synthesized by one microbe that kill or inhibit the growth of other microbes.

Question 42

How does penicillin work?

Answer 42

Mimics part of the bacterial cell wall, preventing cell wall formation, and is bactericidal.

Question 43

What other targets do antibiotics affect?

Answer 43

protein synthesis DNA replication Cell membranes