OBJ - Bacterial Growth & Death

Question 1

Growth curve of bacteria grown in culture

Answer 1

In culture growth proceeds in phases: lag, log, stationery and decline.

Bacterial killing is a factor of activity of agent over time.

Question 2

Predisposing factors that contribute to anaerobic infections

Answer 2

Any of the right:
• Temp
• Moisture
• Oxygen concentration
• Nutrients (C, N, Amino acids, Iron/Sulfur/Phosphorous, etc)

-location in body is anaerobic (i.e. gut)

Question 3

Give an example of a spore-forming organism that causes severe hospital acquired infections.

Answer 3

C Difficile - ETOH doesn’t kill spores; hard to get rid of

Question 4

Describe two methods with which we can determine the number of bacteria present in a liquid medium.

Answer 4

1) Measuring bacterial growth on diluted agar plates & count colonies (colony forming units CFU)

2) Spectrophotometry - measure of “turbidity”
• Light scattering increases with numbers of bacteria
• Inadequate for estimating very low or very high numbers of organisms

Question 5

Aerobe

Answer 5

require O2 for growth
do not ferment substrates
use aerobic respiration, oxidative pathways
examples: Mycobacterium tuberculosis, Pseudomonas aeruginosa

Question 6

Anaerobe

Answer 6

O2 is toxic to them use fermentative metabolism

ex. Clostridium tetani, Clostridium botulinum

Question 7

Microaerophile

Answer 7

(5% O2)
Need O2 - BUT TOO MUCH CAN KILL
use aerobic respiration, not fermentation
Example: Campylobacter jejuni

Question 8

Facultative Anaerobe

Answer 8

• the Swiss Army Knife of Bacteria
• grow in the presence or absence of O2
• use aerobic respiration and fermentation
• Grow FASTER aerobically than anaerobically.
• Example: Escherichia coli

Question 9

Aerotolerant

Answer 9

Tolerate a small amount of O2
use fermentation
Example: Bacteroides fragilis

Question 10

Reasons anaerobes are sensitive to oxygen

Answer 10

Reactive, toxic oxygen molecules:

• singlet oxygen, superoxide free radicals (O2-·)
• peroxide anions (O2-)
• hydroxyl radicals (OH·)

To process/use O2 must have the enzymes:
Superoxide dismutase (SOD)
(202-· + 2H+ –> 02 + H2O2)
and either

Catalase
(2H202 –> 2H20 + 02)

Peroxidase
(H202 + 2H+ –> 2H20)

Question 11

Autoclaving

Answer 11

lab/hospital instruments

Question 12

Ionizing Radiation

Answer 12

most common/done commercially

Question 13

Pasteurization

Answer 13

food/drinks

Question 14

Antisepsis

Answer 14

skin

Use of chemical agents on skin or other tissues to remove or inhibit bacterial agents

Question 15

Filtration

Answer 15

water supply

Question 16

Anaerobic respiration

Answer 16

Electron transport without O2 as e- acceptor

innner membrane of bacteria

Terminal electron acceptor is NOT O2 (NO3-, SO4-2, CO2)
More efficient than fermentation
Less efficient than aerobic respiration

Question 17

Clorox decontamination

Answer 17

kitchen counters

surfaces, generally not to
sterile state

Question 18

Sterilization

Answer 18

Use of physical or chemical means to destroy all microbial forms (vegetative cells and spores).

Question 19

Disinfection

Answer 19

Use of physical or chemical means to destroy most bacterial cells and spores on surfaces and objects.

Question 20

Methods of attacking bacteria

Answer 20

• Membrane disruption by heat, alcohol, phenol, ammonium compounds
• Protein denaturation by heat, alcohol, ionizing radiation
• DNA replication disruption
• UV and ionizing radiation, ethylene oxide
• Oxidization by Chlorine, peroxide

Question 21

Features of culture media

Answer 21

Media contains nutrients that are organism specific/wide variety

All Need:

• Carbon source (typically glucose)
• Water
• Salts
• Nitrogen source = Amino acids

1) Nutritive: most bacteria
2) Enriched: wide variety
3) Selective: selects for certain organisms (i.e. antibiotic resistant strains)
4) Differential: presence of specific nutrients/indicators to visibly indicate the defining characteristic of a microorganism