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Microbiology > Microbial Growth > Flashcards

Microbial Growth Flashcards

1
Q

Define generation time and how do you calculate it

A

time required for a population of microbial cells to double

total number of cells = 2^n ( number of generations)

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2
Q

What two factors effect generation time

A

nutritional and genetic factor

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3
Q

What are the 4 steps to binary fission

A

1) cell elongated and dna is replicated
2) cell wall and plasma membrane begins to constrict
3) cross wall forms, completely seperating the DNA copies
4) cell seperate

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4
Q

What are 2 important proteins for cell division

A

1) Fts ( filamentous temperature sensitive) proteins

2) MreB proteins

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5
Q

Why is Fts proteins important

A

essential for cell division in all prokaryotes

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6
Q

Why is MreB proteins important

A

major shape determining proteins in prokaryotes

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7
Q

What are the 3 physical requirements for growth

A

1) temperature
2) ph
3) Osmotic pressure

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8
Q

What are the 5 chemical requirements for growth

A

1) Carbon
2) Nitrogen,sulfur,and phosphorous
3) trace elements
4) oxygen
5) organic growth factor

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9
Q

Define optimum growth temperture

A

temp at which the species grow best

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10
Q

Define minimum growth temperture

A

lowest temp at which the species will grow

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11
Q

Define maximum growth temp

A

highest temp at which growth is possible

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12
Q

What is the most important factor that effects growth

A

temperture

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13
Q

Most pathogens are classified by what temperture microbe

A

mesophiles

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14
Q

Define psychrophiles

A

cold loving microbes
-10-20 c
optimum is 15

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15
Q

Define psychrotrophs

A

prefer cooler temp ( 0 to 30 c)

causes food spoilage

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16
Q

Define mesophiles

A

moderate temperature loving microbes
(10-50 c)
optimum is 25-40

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17
Q

Define thermophiles

A

heat-loving microbes ( 40-70 c; optimum is 50)

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18
Q

Define hyperthermophiles

A

extreme heat loving microbes

(65-110) optinum is 85-105

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19
Q

What are 3 adaptations extremophiles have

A

1) enzymes and proteins that can withstand extreme hot and cold environment
2) more stronger chemical bonds b/t compounds
3) modifications in the cytoplasmic membrane

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20
Q

Define neutrophiles

A

most bacteria are ph 6.5 and 7.5

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21
Q

What are the ph of molds and yeasts

A

ph 5 and 6

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22
Q

Define acidophiles and 2 species

A

grow in an acidic ph less than 6

exp fungi and archaea

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23
Q

Define alkaliphiles and 2 examples

A

grow in an alkaline ph greater than 9

ex Bacillus species,archaea

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24
Q

What is the most important requirement for growth

A

water

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25
Q

Define osmotic pressure

A

pressure needed to stop the movement of water across the membrane

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26
Q

What does hypertonic environment cause

A

plasmolysis

high solute concentration

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27
Q

Define halophiles

A

have a specific requirement for NaCl

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28
Q

Define extreme or obligate halophiles

A

requires high levels ( 15-30%) of NaCl for growth

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29
Q

Define halotolerant or facultative halophiles

A

can tolerate a high salt concentration, but only require small amount of salt ( 2%) for growth

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30
Q

Define osmophiles

A

live in environment high in sugar

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31
Q

Define xerophiles

A

grow in very dry environments

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32
Q

Define obligate aerobes and 1 example

A

require oxygen

ex. m.luteus

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33
Q

Define facultative anaerobes and 2 examples

A

use oxygen when available but can also grow in absense of oxygen
ex. e.coli and yeasts

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34
Q

Define obligated anaerobes

A

cannot survive in presence of oxygen

ex. c.tetani and c.botulinum

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35
Q

Define aerotolerant anaerobes

A

tolerate but cannot use oxygen

ex s.pyogenes and lactobacillis

36
Q

Define microaerophiles

A

require very low concentrations of oyxgen

ex helicobacter pylori

37
Q

Describe the toxicity of singlet O2

A

higher energy: reactive

02 boosted to a higher energy state

38
Q

Describe the toxicity of superoxide radial O2 (-)

A

strong oxidizer
all organisms attempting to grow in atomospheric oxygen must produce the enzyme ( superoxide dismutase (SOD) to neutralize them

39
Q

Describe hydrogen peroxide ( H2O2) toxicity

A

O2 (2-): oxidizer
produce two enzymes
catalase: convert the hydrogen peroxide to water and oxygen
peroxidase : convert the hp to water

40
Q

Describe hydroxyl radical OH- toxcity

A

most reactive

produce catalase

41
Q

What two types of oxygen toxicity components does aerobes and facultative aerobes have

A

superoxide dismutase and catalase

42
Q

What is the use of carbon in growth

A

structural backbone of organic molecules

43
Q

What are autotrophs carbon source

A

carbon dioxide

44
Q

What are heterotrophs carbon source

A

use organic carbon

45
Q

What is the use of nitrogen,sulfur,phosphorus in growth

A

component of proteins,dna, and ATP

46
Q

What are the 2 sources of nitrogen,sulfur,phosphorus

A

nitrogen fixation

decomposition of proteins

47
Q

What re the use of trace elements and organic growth factors

A

function as cofactors and coenzymes
copper iron zinc are the trace elements
some vitamins and amino acids are organic growth factors

48
Q

Describe biofilms

A

functional microbial communites
form slime or hydrogels that attach to a surface
enclosed in an adhesive matrix

49
Q

What re the advantages of the biofilms

A

self defense
allow cells to remain in a favorable niche
allow cells to live in close association with one another

50
Q

What are problems associated with biofilms

A

involved in 70% of infections

1000x resistant to microbicides

51
Q

Define culture medium

A

nutrients prepared for microbial growth

52
Q

Define sterile

A

no living microbes

53
Q

Define inoculum

A

introduction of microbrobes into a medium

54
Q

Define culture

A

microbes that grow and multiply in a culture medium

55
Q

Define agar

A

complex polysaccharide
used as solidifying agent : petri plates and slates
liquefies at 100 c
solidifies at 40 c

56
Q

What are the 2 types of culture media

A

1) chemical defined media

2) complex media

57
Q

Define chemically defined media

A

exact chemical composition is known

58
Q

Define complex media

A

extracts and digest yeast,meat or plants

contains partially digested proteins called peptones,vitamins and minerals

59
Q

What are 2 types of media

A

nutrient broth and agar

60
Q

Define selective medium

A

suppress unwanted microbes and encourages desired microbes

contains inhibitors to suppress growth

61
Q

What are the 2 plates that have inhibitors for selective medium growth

A

EMB: inhibits gram (+)
MSA: inhibits other microorganisms ( only halophiles can grow)

62
Q

Define MSA

A

mannitol salt agar

63
Q

Define differential medium

A

allow colonies of desired organism to be distinguished from other colonies
ex: blood agar, EMB

64
Q

Can some media have both selective and differential characterisitcs

A

yes

65
Q

Define hemolysis (3 types)

A

alpha,beta,gamma

alpha: parital lyse RBC)
beta: complete lyse of RBC
gamma: no lyse of RBC

66
Q

Define enterotude

A

12 different media

used to figure out microbes that effect urinary/gi

67
Q

Define reducing media

A

contain chemicals ( thioglycolate or oxyrase) that combine o2
it is heated to drive off 02
for anaerobic culture methods

68
Q

Define enrichment culture

A

encourages growth of desired microbes
increasing very small numbers of desired organism to detectable levels
usually liquid medium

69
Q

What 2 ways can you obtain pure culture

A

colony

streak plate method

70
Q

Define colony

A

population of cells arising from single cell or spore or from a group of attached cell
colony forming unit ( CFU)

71
Q

Define streak plate method

A

isolate pure culture

72
Q

What are 2 ways to preserve bacterial culture

A

1) deep freezing ( -50 to 95)

2) lyophilization ( freeze drying)

73
Q

Describe lyophilization as a way to preserve bacterial culture

A

most common
frozen
-54 to -72 and dehydrated in a vacuum

74
Q

Define growth curve

A

increased in bacterial number or mass measured as a function of time

75
Q

What are the 4 phases of growth curve

A

lag phase
log phase/exponential phase
stationary phase
death phase

76
Q

Define lag phase

A

growth rate is essentially zero

enzymes and protein synthesis

77
Q

Define log phase or exponential phase

A

exponenetial growth

population increases

78
Q

Define stationary phase

A

no net increase or decrease in cell #

79
Q

Define death phase

A

the population is decreasing at exponential rate

80
Q

What are the 3 methods of direct measurement of microbial growth

A

1) direct microscopic count
2) plate count
3) filtration

81
Q

What are 3 limitations of direct microscopic count

A

1) cannot distinguish b/t live and dead cells
2) small cells difficult to count
3) motile cells have to be immobilized

82
Q

What is the purpose of viable plate count

A

measurement of living, reproducing population

83
Q

What are 2 methods of viable plate count

A

1) spread plate methods

2) pour plate method

84
Q

Describe serial dilution

A

need to dilute original inoculum with 9ml broth in each tube
10 fold dilution
end product is 1:100000

85
Q

Define plate counts

A

after incubation, count colonies on plate that have 30-300 colonies

86
Q

What is a indirect measurement of microbial growth

A

turbidimetric methods

87
Q

Define turbidity

A

measurement of cloudiness with a spectrophotometer

measure metabolic activity

Microbiology (16 decks)

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