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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
Define osmotic pressure
pressure needed to stop the movement of water across the membrane
26
What does hypertonic environment cause
plasmolysis | high solute concentration
27
Define halophiles
have a specific requirement for NaCl
28
Define extreme or obligate halophiles
requires high levels ( 15-30%) of NaCl for growth
29
Define halotolerant or facultative halophiles
can tolerate a high salt concentration, but only require small amount of salt ( 2%) for growth
30
Define osmophiles
live in environment high in sugar
31
Define xerophiles
grow in very dry environments
32
Define obligate aerobes and 1 example
require oxygen | ex. m.luteus
33
Define facultative anaerobes and 2 examples
use oxygen when available but can also grow in absense of oxygen ex. e.coli and yeasts
34
Define obligated anaerobes
cannot survive in presence of oxygen | ex. c.tetani and c.botulinum
35
Define aerotolerant anaerobes
tolerate but cannot use oxygen | ex s.pyogenes and lactobacillis
36
Define microaerophiles
require very low concentrations of oyxgen | ex helicobacter pylori
37
Describe the toxicity of singlet O2
higher energy: reactive | 02 boosted to a higher energy state
38
Describe the toxicity of superoxide radial O2 (-)
strong oxidizer all organisms attempting to grow in atomospheric oxygen must produce the enzyme ( superoxide dismutase (SOD) to neutralize them
39
Describe hydrogen peroxide ( H2O2) toxicity
O2 (2-): oxidizer produce two enzymes catalase: convert the hydrogen peroxide to water and oxygen peroxidase : convert the hp to water
40
Describe hydroxyl radical OH- toxcity
most reactive | produce catalase
41
What two types of oxygen toxicity components does aerobes and facultative aerobes have
superoxide dismutase and catalase
42
What is the use of carbon in growth
structural backbone of organic molecules
43
What are autotrophs carbon source
carbon dioxide
44
What are heterotrophs carbon source
use organic carbon
45
What is the use of nitrogen,sulfur,phosphorus in growth
component of proteins,dna, and ATP
46
What are the 2 sources of nitrogen,sulfur,phosphorus
nitrogen fixation | decomposition of proteins
47
What re the use of trace elements and organic growth factors
function as cofactors and coenzymes copper iron zinc are the trace elements some vitamins and amino acids are organic growth factors
48
Describe biofilms
functional microbial communites form slime or hydrogels that attach to a surface enclosed in an adhesive matrix
49
What re the advantages of the biofilms
self defense allow cells to remain in a favorable niche allow cells to live in close association with one another
50
What are problems associated with biofilms
involved in 70% of infections | 1000x resistant to microbicides
51
Define culture medium
nutrients prepared for microbial growth
52
Define sterile
no living microbes
53
Define inoculum
introduction of microbrobes into a medium
54
Define culture
microbes that grow and multiply in a culture medium
55
Define agar
complex polysaccharide used as solidifying agent : petri plates and slates liquefies at 100 c solidifies at 40 c
56
What are the 2 types of culture media
1) chemical defined media | 2) complex media
57
Define chemically defined media
exact chemical composition is known
58
Define complex media
extracts and digest yeast,meat or plants | contains partially digested proteins called peptones,vitamins and minerals
59
What are 2 types of media
nutrient broth and agar
60
Define selective medium
suppress unwanted microbes and encourages desired microbes | contains inhibitors to suppress growth
61
What are the 2 plates that have inhibitors for selective medium growth
EMB: inhibits gram (+) MSA: inhibits other microorganisms ( only halophiles can grow)
62
Define MSA
mannitol salt agar
63
Define differential medium
allow colonies of desired organism to be distinguished from other colonies ex: blood agar, EMB
64
Can some media have both selective and differential characterisitcs
yes
65
Define hemolysis (3 types)
alpha,beta,gamma alpha: parital lyse RBC) beta: complete lyse of RBC gamma: no lyse of RBC
66
Define enterotude
12 different media | used to figure out microbes that effect urinary/gi
67
Define reducing media
contain chemicals ( thioglycolate or oxyrase) that combine o2 it is heated to drive off 02 for anaerobic culture methods
68
Define enrichment culture
encourages growth of desired microbes increasing very small numbers of desired organism to detectable levels usually liquid medium
69
What 2 ways can you obtain pure culture
colony | streak plate method
70
Define colony
population of cells arising from single cell or spore or from a group of attached cell colony forming unit ( CFU)
71
Define streak plate method
isolate pure culture
72
What are 2 ways to preserve bacterial culture
1) deep freezing ( -50 to 95) | 2) lyophilization ( freeze drying)
73
Describe lyophilization as a way to preserve bacterial culture
most common frozen -54 to -72 and dehydrated in a vacuum
74
Define growth curve
increased in bacterial number or mass measured as a function of time
75
What are the 4 phases of growth curve
lag phase log phase/exponential phase stationary phase death phase
76
Define lag phase
growth rate is essentially zero | enzymes and protein synthesis
77
Define log phase or exponential phase
exponenetial growth | population increases
78
Define stationary phase
no net increase or decrease in cell #
79
Define death phase
the population is decreasing at exponential rate
80
What are the 3 methods of direct measurement of microbial growth
1) direct microscopic count 2) plate count 3) filtration
81
What are 3 limitations of direct microscopic count
1) cannot distinguish b/t live and dead cells 2) small cells difficult to count 3) motile cells have to be immobilized
82
What is the purpose of viable plate count
measurement of living, reproducing population
83
What are 2 methods of viable plate count
1) spread plate methods | 2) pour plate method
84
Describe serial dilution
need to dilute original inoculum with 9ml broth in each tube 10 fold dilution end product is 1:100000
85
Define plate counts
after incubation, count colonies on plate that have 30-300 colonies
86
What is a indirect measurement of microbial growth
turbidimetric methods
87
Define turbidity
measurement of cloudiness with a spectrophotometer | measure metabolic activity

Microbiology (16 decks)

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