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MICR 262 > (LE2) Microbial Growth and Control > Flashcards

(LE2) Microbial Growth and Control Flashcards

1
Q

What physical requirements are needed to be optimal for bacterial growth?

A
  1. temperature
  2. pH
  3. osmotic pressure
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2
Q

What are mesophiles? Give an example

A

Bacteria with optimal growth temperature of 37 degrees Celsius (human body temperature)
- pathogens
- Escherichia

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3
Q

What are psychrophiles? Give an example

A

Bacteria with very cold optimum temperatures. Thrive in fridge
Flavobacterium

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4
Q

What are thermophiles? Give an example

A

Bacteria with a very hot optimal growth temperature. Thrive near thermal vents
Thermus, Thermococcus

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5
Q

What are acidophiles? Give an example

A

bacteria that prefer low pH
e.g. Helicobacter pylori (cause ulcers)

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6
Q

How do we prevent drops in pH when culturing bacteria?

A

Adding buffers

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7
Q

What byproduct is produced when bacteria eat sugars? Proteins?

A

Sugar = acid byproduct
Proteins = base byproduct

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8
Q

Why are salt and sugar used as food preservatives?

A

Cause solute concentration around bacteria to be hypertonic, which causes plasmolysis

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9
Q

What are halophiles? Give an example

A

Bacteria that prefer higher than normal salt concentration
e.g. Staphylococcus aureus (common cause of food poisoning)

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10
Q

What common nutritional requirements do all cells have? Why?

A

All needed for cellular energy and building organic molecules
- carbon
nitrogen (proteins and nucleic acids)
phosphorus (nucleic acids and lipids)
sulfur (proteins)

  • trace elements (mostly enzyme co-factors)
  • vitamins and other organic growth factors (co-enzymes)
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11
Q

What is normally formulated in nutrient agar and for what purpose?

A

Extracts and digests (beef protein)
- general growth

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12
Q

What is normally formulated in enriched media and for what purpose?

A

extra ingredients like blood in BAP, for certain growth requirements

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13
Q

What is chemically defined media? Give an example

A

Growth media formulated with specific ingredients to grow specific organisms
- e.g. citrate agar

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14
Q

What growth media is used to measure microbial oxygen requirements?

A

Thioglycollate broth: O2 concentration gradient. Present at top, absent on bottom

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15
Q

What enzymes are required for protection against oxidative damage?

A

Superoxide dismutase and catalase

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16
Q

What are obligate aerobes? What is their appearance in Thioglycollate broth? What enzymes do they have against oxidative damage?

A
  • Use aerobic respiration only
  • contain both Superoxide dismutase and catalase
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17
Q

What are facultative anaerobes? What is their appearance in Thioglycollate broth? What enzymes do they have against oxidative damage? Provide an example.

A
  • use aerobic respiration if O2 available and anaerobic pathways if not
  • contain both Superoxide dismutase and catalase
  • majority of bacteria
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18
Q

What are aerotolerant anaerobes? What is their appearance in Thioglycollate broth? What enzymes do they have against oxidative damage?

A
  • do not use O2 but can survive if present
  • contains only Superoxide dismutase
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19
Q

What are microaerophiles? How do they appear in Thioglycollate broth? What enzymes do they have against oxidative damage? Provide an example.

A
  • use aerobic respiration, but require low O2 concentration, ~ 1%
  • contains both Superoxide dismutase and catalase at low concentration
  • Neisseria gonorrhoeae
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20
Q

What are obligate anaerobes? What is their appearance in Thioglycollate broth? What enzymes do they have against oxidative damage? Provide an example.

A
  • do not use aerobic respiration. O2 is toxic
  • contains no enzyme against oxidative stress
  • Clostridium difficil
21
Q

What waste is produced after aerobic respiration? What does it do?

A

superoxide (O2-) - highly reactive, damages DNA, proteins, etc.

22
Q

How do SOD and catalase work against superoxides?

A
  • SOD neutralizes O2- with H2O to make H2O2 (hydrogen peroxide)
  • Catalase neutralizes H2O2 into water and oxygen
23
Q

What stage of the bacterial growth curve is indicated in the picture? What occurs in that phase?

A

Lag Phase
- acclimation to new environment

24
Q

What stage of the bacterial growth curve is indicated in the picture? What occurs in that phase?

A

Log Phase
- Max rate of exponential growth
- birth rate > death rate

25
Q

What stage of the bacterial growth curve is indicated in the picture? What occurs in that phase?

A

Stationary Phase
- Running out of food
- birth rate = death rate

26
Q

What stage of the bacterial growth curve is indicated in the picture? What occurs in that phase?

A

Decline/death phase
- death rate > birth rate

27
Q

At what phase in the growth curve will bacteria begin to produce endospores?

A

Stationary phase

28
Q

What is sterilization?

A

killing or removal of all microorganisms on a material or object

29
Q

What is disinfection? What two agents are used for disinfection?

A
  • reduction of the number of pathogenic microorganisms to the point they pose no danger of disease
  • antiseptics and disinfectants
30
Q

What are antiseptics?

A

chemical agent that can be safely used on living tissue to destroy or inhibit growth of microorganisms

31
Q

What are disinfectants?

A

Chemical agent used on inanimate objects to destroy microorganisms. Don’t kill spores

32
Q

What is a bacteriostatic agent?

A

Chemical agent that inhibits the growth of bacteria

33
Q

What is a bacteriacide?

A

An agent that kills bacteria. Most do not kill spores

34
Q

How does growth rate influence microbial control?

A

faster growth rate = easier to kill
slower growth rate = harder to kill

35
Q

How does temperature influence microbial control?

A

chemical agents work slower at colder temperatures

36
Q

How does the type/number of microbes affect microbial control?

A

some microbes are more difficult to kill

37
Q

How does the environment influence microbial control?

A

some chemical agents are deactivated by the presence of other organic compounds (i.e. blood, pus, feces, etc.)

38
Q

Describe the different methods of heating used to control growth

A

Dry heat: effective, but slow (incineration, oven)

Moist heat: - Boiling: doesn’t kill spores
- autoclave: superheated steam (121*C) under pressure (15 PSI) = sterilization
Soft heat: pasteurization: not sterile ; leaves some microbes

39
Q

Why would we use filtration as a method of control? What are the different pore sizes?

A

Used for heat-labile substances (vaccines and medication)

  • 0.45 microns: bacteria
  • 0.05 microns: viruses
40
Q

What methods of control do we use with low temperature and drying?

A

Refrigeration: bacteriostatic
Desiccation: spores survive
Lyophilization: freeze-drying

41
Q

How is osmotic pressure a method of control?

A

causes plasmolysis

42
Q

How is radiation a method of control? What are the types of radiation?

A

Damages DNA and proteins

Ionizing: penetrating (e.g. x-rays and gamma rays)
Non-ionizing: good for surfaces (e.g. UV light)

43
Q

How do soaps and detergents work? Give an example

A

They are surfactants (like phospholipids), damages cell membranes
- quaternary ammonium compounds (mopping solutions) for surfaces

44
Q

How do phenol and it’s derivatives work? Give an example

A

Damage membranes and denature proteins
- not inhibited by organic materials
e.g. Lysol or Cholorohexidine

45
Q

How do alcohols work? Give an example

A

Highly effective in damaging membranes and denature proteins
- safe for skin
- evaporates quickly
e.g. hand sanitizer

46
Q

How do organic acids work? Give an example

A

Bacteriostatic by slowing /preventing fermentation
e.g. food preservatives

47
Q

How do halogens work? Give an example

A

Damages proteins
e.g. Chlorine and Iodine (antiseptic)

47
Q

How do heavy metals work? Give an example

A

Damages proteins
- silver nitrate: newborn eyedrops
- organic mercury: antisepsis

47
Q

How do oxidizing agents work? Give an example

A

Denature proteins
e.g. peroxide (antiseptic)

MICR 262 (30 decks)

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