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Microbiology > Lecture 3: Cultivation of Bacteria > Flashcards

Lecture 3: Cultivation of Bacteria Flashcards

1
Q

What is bacterial growth and what is it dependent on

A

Population growth/ increase number of cells

Dependent on nutritional factors and other environmental factors

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2
Q

What are some abiotic environmental factors that influence bacterial growth

A

Temperature, pH, oxygen, carbon dioxide, water availability/ osmotic pressure

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3
Q

What is the minimum, optimum, and maximum temperatures for mesophils

A

Minimum: 10 C
Optimum: 37 C
Maximum: 50 C

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4
Q

What is the optimal pH for most bacteria

A

6.5-7.5

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5
Q

Transport media and cultured media are usually buffered at what pH

A

7

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6
Q

In terms of oxygen, bacteria are categorized based what two things

A
  1. Requirement for oxygen in metabolic pathways
  2. Ability to counteract ROS
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7
Q

Do obligate aerobes require oxygen and do they have enzymes for ROS

A

Yes to both

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8
Q

Do microaerphile require oxygen and do they have enzymes against ROS

A

Oxygen: yes but at reduced levels and have enzyme to counteract ROS

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9
Q

Do facultative anaerobes require oxygen and do they have enzyme against ROS

A

Don’t require O2 but will use if available, and have enzyme against ROS

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10
Q

Do obligate anaerobes require oxygen and do they have enzyme against ROS

A

No- oxygen is toxic, and don’t have enzyme against ROS

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11
Q

What are some examples of special sampling and growth conditions needed for obligate anaerobes

A
  1. Anaerobic transport media
  2. Reducing culture media
  3. Anaerobic jars, bags or chambers
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12
Q

What are capnophiles

A

Organisms that require 5-10% CO2 for optimal growth

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13
Q

What are some ways er can elevate CO2 for capnophiles

A
  1. Candle jar
  2. CO2 packet
  3. CO2 incubator
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14
Q

What is the purpose of the transport media to prevent desiccation

A

Provide moisture until sample can be cultured

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15
Q

T or F: endoscopes resist desiccation

A

True and they contaminate cultures

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16
Q

What are halotolerant bacteria

A

Bacteria that don’t require NaCl but can grow under saline conditions (increased osmotic pressure)

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17
Q

What does it mean for bacteria to be chemohetertrophs

A

Use organic compounds as sources of energy or carbon

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18
Q

What are fastidious bacteria

A

Bacteria that require additional organic compounds/ vitamins in their culture media

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19
Q

What are some examples of growth factors

A

Vitamins, amino acids, purines, pyrimidines

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20
Q

Where are growth factors obtained from

A

Microbes environment

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21
Q

___ Taxa typically require a large number of growth factors

A

Fastidious

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22
Q

What is a liquid media ideal for and what can’t it do

A

Growing large numbers of bacteria

Can’t visually determine number and species present

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23
Q

What is a solid media (agars) used for

A

Isolation of pure cultures, estimating the number of viable bacteria

Colony characteristics useful for ID

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24
Q

What is a colony

A

Population of cells arising from a single cell, spore or from a group of cells of the same species and strain

25
Q

T or F: agar is a nutrient

A

False it is a solidifying agent

26
Q

What are semi-solid agars used for

A

Determining motility, growing microaerophiles, some transport media

27
Q

What type of bacteria can a basal media sustain the growth of

A

Less fastidious bacteria

28
Q

What are some examples of basal medias

A

Nutrient agar, nutrient broth, tryptic soy agar

29
Q

What is enriched media and what is it used for

A

Basal media and additional nutrients (blood, egg yolk) used for fastidious organisms

30
Q

What are some examples of enriched media

A

Blood agar, chocolate agar

31
Q

What are selective medias

A

Reagents (dyes, NaCl0 added that inhibit the growth of unwanted bacteria while allow the growth of others

32
Q

What are some examples of selective medias

A

MacConkey and mannitol salt agar

33
Q

What is MacConkey agar specific for

A

Gram negative bacteria- bile salts inhibit gram positive

34
Q

What is mannitol salt agar used for

A

Gram positive

35
Q

What are differential media

A

Contain components (dyes, ph) that allow the differentiation of closely related taxa based on the appearance (color) of the colony or surrounding media

36
Q

What are some examples of differential media

A

MacConkey agar, mannitol salt agar, sheep blood agar

37
Q

How is MacConkey agar used as differential media

A

Bacteria that breakdown lactose will result in a red/pink/purple color ex: E. Coli

No lactose but gram negative will be white

38
Q

How is mannitol salt agar used as differential agar

A

Changes from pink—> yellow

Ex: S. Aureus

39
Q

How is sheep blood agar used as differential media

A

Shows hemolysis

40
Q

What is a transport media used for

A

Transport of clinical specimens to lab, preserve microbial viability and help maintain the original ratio of microbes in the clinical sample. No nutrients because don’t want microbes to compete with each other and change ratio

41
Q

What is an example of a bacteria that is an obligate intracellular bacteria- grown in animal cells

A

Rickettsia spp

42
Q

What bacteria is cultivated in armadillos or immunodeficiency mice

A

Mycobacterium leprae

43
Q

What are the goals of preserving a pure culture

A
  1. Viability
  2. Purity
  3. Genetic stability
44
Q

How does subculture work to preserve bacterial cells

A

Transfer cells to fresh medium, incubate, refrigerate and repeat every 2-3 weeks

45
Q

How does snap-freeze cells in broth with cryopreservative preserve bacterial cells

A

Store in freezers or liquid nitrogen

Repeated thawing/freezing reduced viability

46
Q

What is the most common mode of bacterial growth

A

Binary fission

47
Q

What is generation time

A

Time required for population to double

48
Q

What is generation time for most bacteria

A

1-3hrs

49
Q

What is generation time for E. Coli

A

20 minutes

50
Q

What is generation time for mycobacterium leprae

A

14 days

51
Q

What is the lag phase in bacterial growth curve

A

No cell division, cells preparing for growth, duration determined by nutrient types/quanities

52
Q

What is the log phase in bacterial growth curve

A

Exponential growth, primary metabolites produced

53
Q

What cells in bacterial growth curve are highly vulnerable to antibiotics and detrimental environmental conditions

A

Log phase cells

54
Q

What is the stationary phase in bacterial growth curve

A

Zero population growth due to nutrient depletion and waste product toxicity, secondary metabolites produced

55
Q

What is the death/decline phase

A

Exponential death, some bacteria enter long term stationary phase that can last for years

56
Q

What is a batch culture

A

Growth in a closed system, exponential growth can’t be maintained

57
Q

What is continuous culture

A

Growth in a chemostat, fresh medium continuously added, waste continuously removed, exponential growth can be maintained

58
Q

Cells entering stationary/decline phase are where on solid media (agar)

A

Center

59
Q

Cells entering exponential growth phase are where on solid media/ agar

A

Edges

Microbiology (31 decks)

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