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Microbial world > Lecture 7 and 8 > Flashcards

Lecture 7 and 8 Flashcards

1
Q

What are the 5 shapes of colonies?

A

Circular, rhizoid, irregular, filamentous, spindle

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2
Q

What are the 6 possible margins of a colony?

A

Entire, undulate, lovate, cruled, rhizoid, filamentous

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3
Q

What 4 elevations can a colony have?

A

Flat
Raised
Convex
Umbonate

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4
Q

What is the smallest colony size?

A

Punctiform

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5
Q

Bacteria within a colony can be genetically identical but, they can be…

A

Metabolically different

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6
Q

Define binary fission

A

Division into 2 equally sized daughter cells

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7
Q

What happens during binary fission?

A

Cell elongates/replicates DNA
Cell wall/plasma mebrane constrict
Cross wall forms
Cells separate

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8
Q

Define generation time

A

Time required for cell to divide

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9
Q

What is generation time for E.coli in nutrient rich medium at 37?

A

30 minutes

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10
Q

What is the generation time for Mycobacterium tuberculosis?

A

15-20 hours

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11
Q

What is the advantage of using logarithmic scale over non-logarithmic scale when representing bacterial populations?

A

Possible to predict the number of cells that will be produced over a certain time period

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12
Q

Why is there a lag phase?

A

New cultures usually come from cultures in stationary phase/ death phase (not adjusted to new environmnet)

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13
Q

What phase comes after lag phase?

A

Log phase

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14
Q

What happens during log phase?

A

High metabolic activity: cells divide, exponential growth

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15
Q

What phase comes after log phase?

A

Stationary phase

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16
Q

Why stationary phase?

A

Cells run out of nutrients, metabolic changes pH, waste products accumulate (equilibrium)

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17
Q

What phase comes after the stationary phase?

A

Death phase

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18
Q

Name three indirect methods of measuring microbial growth.

A

Turbidity
Metabolic activity
Dry weight

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19
Q

Name 4 direct methods of measuring microbial growth.

A

Plate counts
FIltration
Microscopic count
Most probable number (MPN)

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20
Q

What is turbidity as an indirect method for measuring microbial growth?

A

The use of a spectrophotometer to measure percentage transmission in suspended cells

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21
Q

What is a disadvantage to turbidity?

A

If bacteria change morphology in growth phases, turbidity changes
Cells may aggregate

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22
Q

What is metabolic activity as an indirect method for measuring microbial growth?

A

The amount of certain metabolic products is directly proportional to number of bacteria (e.g. acid or CO2 production)

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23
Q

What is dry weight as an indirect method of measuring microbial growth?

A

Cells removed from media, filtered, dried, weighted

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24
Q

What is a plate count?

A

Serial dilution of population, the number of cells is expressed as colony forming units (CFU)

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25
Q

How is the amount of bacteria in the original sample calculated using plate counts?

A

Count colonies on plate, multiply by dilution factor

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26
Q

What are the two types of plate count?

A

Pour plate method

Spread plate method

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27
Q

What type of bacteria can be grown using the pour plate method?

A

Facultative anaerobic bacteria (problematic if bacteria are temperature sensitive)

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28
Q

What is the filtration method of measuring microbial growth?

A

Bacteria are filtered and the filter is placed on a growth medium

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29
Q

When is filtration used to measure microbial growth?

A

When quantity of bacteria is very small (e.g. samples from lakes/ streams)

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30
Q

How does the MPN (most probable method) measure microbial growth?

A

Dilute to reduce density to which no bacteria are left to grow in tubes

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31
Q

When is MPN useful?

A

When microbes will not grow on solid media

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32
Q

What is MPN?

A

The statistical estimation of number of cells

33
Q

What are the two main requirement catagories for bacterial growth?

A

Physical requirements

Chemical requirements

34
Q

What name is given to bacteria that grow between ~-10-20 degrees C?

A

Psychrophiles

35
Q

What name is given to bacteria that grows between 0 and 30 degrees C?

A

Psychrotrophs

36
Q

Between which temperatures do mesophiles grow?

A

10 and 50 degrees

37
Q

Between which temperatures do thermophiles grow?

A

40 and 70

38
Q

What name is given to bacteria that grows between 65 and 110 degrees?

A

Hyperthermophiles

39
Q

How do psychrophiles keep their fatty acids remaining fluid?

A

Proeinaceous antifreeze

40
Q

Name a psychrotroph that grows in fridges.

A

Listeria monocytogenes

41
Q

Name a mesophile.

A

E.coli

42
Q

Name a thermophile

A

Sulfolobus (e.g. Yellowstone national park hotsprings)

43
Q

What are the red/brown bacteria in Grand pismatic spring?

A

Pigmented bacteria (carotenoid) gives protection from light

44
Q

Name a hyperthermophile.

A

Thermothoga maritima (lives in hydrothermal vents)

45
Q

What is the temperature growth record?

A

121C

46
Q

What pH do acidophiles grow at?

A

pH below 7

47
Q

What pH do moderate acidophiles grow between?

A

3-5

48
Q

What name is given to acidophiles that grow below pH 3?

A

Extreme acidophiles

49
Q

What bacteria grow between pH 6.5 and 7.5?

A

Most bacteria

Neutrophiles

50
Q

What type of bacteria grows at pH 9-12?

A

Alkaliphiles

51
Q

What does hypertonic environments cause?

A

Plasmolysis

52
Q

What name is given to bacteria that require high external solute concentration?

A

Extreme/obligate halophiles

53
Q

What name is given to bacteria that can tolerate high external solute concentrations?

A

Facultative halophiles

54
Q

Why do bacteria require nitrogen?

A

Protein synthesis
DNA
RNA
ATP

55
Q

Where do bacteria obtain nitrogen from?

A

Amino acids
NH4+
NO3-
Gaseous N2

56
Q

Why do bacteria require sulfur?

A

Protein synthesis, vitamins

57
Q

Where do bacteria obtain sulfur from?

A

Amino acids
SO4^2-
Hydrogen sulfide

58
Q

Why do bacteria require phosphorus?

A

DNA, RNA, ATP

59
Q

Where do bacteria obtain phosphorus from?

A

PO4^3-

60
Q

What are trace elements?

A

Inorganic elements require in small amounts for co-factors in enzymes

61
Q

Name some trace elements

A

Iron, copper, zinc

62
Q

What are organic growth factors?

A

Organic compounds obtained from the environment

63
Q

Name some organic growth factors

A

Vitamins
Amino acids
Purines
Pyrimidines

64
Q

What bacteria have only aerobic growth (oxygen required)?

A

Obligate aerobes

65
Q

What bacteria have both anaerobic and aerobic growth?

A

Facultative anaerobes

66
Q

What bacteria only grows anaerobically?

A

Obligate anaerobes

67
Q

What name is given to bacteria that only grows anaerobically, but continues in the presence of oxygen?

A

Aerotolerant anaerobes

68
Q

What name is given to bacteria that only grow in aerobic conditions, but oxygen is required in low concentration?

A

Microaerophiles

69
Q

Why can oxygen be toxic?

A 
Singlet oxygen (O2-) Higher energy state
Peroxide anion (O2^2-) contained in H2O2
70
Q

What enzyme detoxifies peroixide anions?

A

Superoxide dismutase (SOD) turns it back to H2O2

71
Q

What enzyme turns H2O2 into water and oxygen?

A

Catalase

72
Q

What enzyme turns H2O2 into water in the presence of hydrogen?

A

Peroxidase

73
Q

How do bacteria communicate in biofilms?

A

Quorum sensing

74
Q

What do nutrient agar’s typically contain?

A 
Peptone
Beef extract
Sodium chloride
Agar
Water
75
Q

What is peptone? Why is it added?

A

Partially digested protein

Energy, carbon, nitrogen, sulfur

76
Q

Why is beef extract in agar?

A

Vitamins, organic growth factors

77
Q

What are two types of medium?

A

Selective medium, differential medium

78
Q

What is an enrichment culture?

A

Similar to selective medium, but increases number of desired microbes to detectable levels

Microbial world (12 decks)

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