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Clinical Microbiology > (exam 1) chapter 6 microbial growth > Flashcards

(exam 1) chapter 6 microbial growth Flashcards

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1
Q

what are two broad requirements for growth?

A

physical and chemical requirements

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2
Q

what are three physical requirements?

A

1) temperature
2) pH
3) osmotic pressure

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3
Q

what are five chemical requirements?

A

1) Carbon
2) Nitrogen, sulfur, and phosphorous
3) Trace elements
4) Oxygen
5) Organic growth factors

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4
Q

what type of growth requirement is oxygen?

A

chemical requirement!

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5
Q

what are extremophiles?

A

microbes that thrive in physical or chemical conditions that typically kill most microbes

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6
Q

when do microbes grow well regarding temperature?

A

in a limited temperature range- optimum (best temperature for fastest growth)

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7
Q

what are three primary groups based on preferred temperature ranges?

A

1) meophiles
2) psychrophiles
3) thermophiles

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8
Q

what are mesophiles?

A

moderate-temperature-loving (25-40oC)

Most common type of microbe (not extremophiles)

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9
Q

what are psychrophiles?

A

cold-loving (15oC)

Found in polar regions or deep within the ocean

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10
Q

what are thermophiles?

A

heat-loving (50-60oC)

Found in hot springs and sunlit soil

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11
Q

what are psychrotrophs?

A

psychrophiles that can cause food spoilage (20-30oC)

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12
Q

what are Hyperthermophiles?

A

thermophiles that grow at much higher temperatures than thermophiles (≥80oC)

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13
Q

what pH do most bacteria grow near?

A

most bacteria grow near neutral pH (6-8)

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14
Q

acids produced during bacterial fermentation do what?

A

inhibit growth (food preservation)

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15
Q

what pH do molds and yeasts grow between?

A

pH 5 and 6

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16
Q

what are Acidophiles?

A

bacteria that grow in acidic environments- such as the Stomach

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17
Q

what are Alkaliphiles?

A

bacteria that grow in basic environments

alkali lakes and desert soil

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18
Q

what is the concentration of hypertonic solutions?

A

Hypertonic solutions contain a higher concentration of solutes (i.e. NaCl) than inside the cell and water moves out of the cell.

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19
Q

what do hypertonic solutions cause?

A

plasmolysis

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20
Q

what is plasmolysis?

A

(shrinkage of the cell cytoplasm) due to high osmotic pressure

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21
Q

what are halophiles?

A

bacteria that requires high osmotic pressure

Found in Great Salt Lake

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22
Q

what is the concentration of hypotonic solutions?

A

solute concentration is lower outside than inside the cell; water moves into cell

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23
Q

what type of solutions do most bacteria live in?

A

hypotonic solutions

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24
Q

what is the importance of the cell wall?

A

Cell wall prevents osmotic lysis (Plasma membrane rupture due to excess water moving into cell)

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25
Q

most bacteria (like most organisms) are what mode of nutrition?

A

heterotrophs (use organic molecules as a carbon source)

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26
Q

what are nitrogen, sulfur, and phosphorous?

A

Synthesis of proteins, nucleic acids, phospholipids, ATP, and vitamins

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27
Q

what are trace elements?

A 
Inorganic elements (i.e. iron, copper, zinc) 
Required in small amounts, typically enzyme cofactors
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28
Q

what are organic compounds?

A

Cannot be synthesized; obtained from the environment; Often are vitamins that act as enzyme cofactors

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29
Q

what do we know about microbes that use molecular oxygen?

A

they obtain more energy from nutrients than those that do not

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30
Q

when is O2 very toxic?

A

O2 radicals “steal” electrons from other molecules, converting them to dangerous forms and disrupting essential cellular processes

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31
Q

what type of immune cells in humans use these radical forms of O2 to destroy pathogens?

A

Phogocytic immune cells

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32
Q

bacteria that grow in the presence of O2 produce what?

A

superoxide dismutase (SOD)

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33
Q

what is superoxide dismutase (SOD)?

A

Enzyme that converts superoxide radicals (O2−) into molecular oxygen (O2) and hydrogen peroxide (H2O2)

34
Q

is the peroxide anion (O22-) of hydrogen peroxide toxic?

A

yes

35
Q

what is The peroxide anion (O22-) of hydrogen peroxide converted by?

A

catalase or peroxidase

36
Q

(oxygen requirement for) Obligate aerobes?

A

require oxygen

37
Q

(oxygen requirement for) Facultative anaerobes?

A

grow via fermentation or anaerobic respiration when oxygen is not available

38
Q

(oxygen requirement for) Anaerobes?

A

unable to use oxygen and most are harmed by it

39
Q

(oxygen requirement for) Aerotolerant anaerobes?

A

tolerate but cannot use oxygen

40
Q

(oxygen requirement for) Microaerophiles

A

require oxygen concentration lower than air

41
Q

what is a culture?

A

microbes growing in or on a culture medium

42
Q

what is Inoculum?

A

when microbes are introduced into a medium

43
Q

what is Culture/Growth media?

A

Nutrients prepared for microbial growth

44
Q

what are two criteria’s for growth?

A

1) Physical and chemical requirements of microbe must be met

2) Starting media must be sterile

45
Q

what does sterile mean?

A

contain no living microbes`

46
Q

what are two main forms of culture media?

A

1) Liquid (broth) media

2) Solid media (contain agar)

47
Q

what is ager?

A

solidifying agent for culture media; Complex polysaccharide isolated from marine algae

48
Q

what three things can ager be used to create?

A

1) petri plates
2) slants
3) deeps

49
Q

what are petri plates?

A

shallow dishes with a lid to prevent contamination (Useful for examining colony morphology, counting colonies, and preparing pure cultures)

50
Q

what are slants?

A

agar solidifies while the tube is at an angle (Increases the surface area for growth)

51
Q

what are deeps?

A

agar solidifies in a vertical tube

Used to examine gas requirements of microbes

52
Q

what are two main categories of media?

A

1) Chemically defined media

2) Complex media

53
Q

what is Chemically defined media ?

A

exact chemical composition is known - pricy

Fastidious (picky eaters) organisms require many growth factors provided in chemically defined media

54
Q

what is Complex media?

A

extracts and digests of yeasts, meat, or plants; chemical composition varies batch to batch; typically feeds many different types of bacteria
nutrient broth - liquid complex media
nutrient agar - solid complex media

55
Q

what do anaerobic cultures require?

A

reducing media; Contain ingredients that deplete O2
Sodium thioglycollate
- Medium is anaerobic after preparation, but O2 diffuses in over time, creating an oxygen gradient

56
Q

what are Capnophiles?

A

Microbes that require high CO2 conditions

57
Q

what is Selective media ?

A

suppress unwanted microbes and encourage desired microbes

-Contain inhibitors to suppress growth

58
Q

what are Differential media?

A

distinguishes between different microbe colonies growing on the same plate
-Media can have selective and differential characteristics

59
Q

what is enrichment media?

A

– favors growth of a particular microbe that is in very small numbers; Like selective media but growth of other microbes is not inhibited

60
Q

What is the streak plate method used for?

A

to isolate individual bacterial colonies

61
Q

what is a colony?

A

is a population of cells arising from a single cell or spore or from a group of attached cells
A colony is often called a colony-forming unit (CFU)

62
Q

what is a pure culture?

A

a culture containing only the microbe of interest; Aseptic technique is critical for the creation and maintenance of pure cultures

63
Q

What is inoculum?

A

the substance used for inoculation

64
Q

what is bacteria growth?

A

when bacteria increase in cell number (not cell size)

65
Q

how to bacteria reproduce?

A

typically through binary fission where one parent cell splits into two new cells

66
Q

what is generation time?

A

time required for a cell to divide (20min-24hrs)

67
Q

how are bacteria growth curves represented and why?

A

typically represented logarithmically because arrhythmic graphs are not meaningful

68
Q

what are the four main phases of bacteria growth curves?

A

1) Lag phase (intense activity preparing for growth but no increase in population)
2) Log phase (logarithmic / exponential increase in the population)
3) stationary phase (period of equilibrium; microbial deaths balance production of new cells)
4) death phase (population is decreasing at a logarithmic rate)

69
Q

what can stationary and death phase be due to?

A

factors such as accumulation of waste, depletion of available nutrients, pH changes, etc.

70
Q

what are four ways of counting microbial cells?

A

1) plate count
2) filtration
3) most probable number MPN method
4) direct microscopic count

71
Q

what range of microbial colonies is best for plate counts?

A

30-300 colonies (CFUs)

72
Q

what is the purpose of a serial dilution?

A

when you perform a serial dilution of the original sample it provides plates with 30-300 colonies for accurate measurement (plate count)

73
Q

what two methods work with plate counts?

A

counts performed on plates that used pour plate method (bacteria mixed into a dish with agar) or spread plate method (bacteria spread on the surface)

74
Q

what is the filtration counting method?

A

Solution passed through a filter that collects bacteria; Filter is transferred to a Petri dish and grows as colonies on the surface

75
Q

what is the most probable number MPN method counting method?

A

Often used for water analysis; Statistical estimating technique-Count positive tubes and compare with a statistical table

76
Q

what is direct microscopic count method?

A

Volume of a bacterial suspension placed on a slide; Average number of bacteria per viewing field is calculated

77
Q

what is turbidity (indirect measurement of bacteria growth)?

A

measurement of cloudiness with a spectrophotometer

78
Q

what are three ways to indirectly measure bacteria growth?

A

1) turbidity
2) metabolic activity
3) dry weight

79
Q

what is metabolic activity (indirect measurement of bacteria growth)?

A

amount of metabolic product is proportional to the number of bacteria

80
Q

what is dry weight (indirect measurement of bacteria growth)?

A

bacteria are filtered, dried, and weighed; used for filamentous organisms

Clinical Microbiology (17 decks)

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