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microbiology > chapter 4 microbial growth > Flashcards

chapter 4 microbial growth Flashcards

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Biology 101 flashcards
1
Q

bacterial growth refers to increase in bacterial cell numbers or does it refer to the increase of size of individual cells?

A

it refers to the increase in bacterial cell numbers

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2
Q

how do most bacteria reproduced ?

A

most of them reproduce by binary fission

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3
Q

define the characteristics of bacteria cell

A

elongates and makes a copy of its DNA, divides into two identical cells which we call the daughter cells.

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4
Q

exponential growth:
As we re-call bacteria divide by binary fission, what does this indicate for the population of cells ?

A

it will double every generation

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5
Q

what is the term called for the time required for population to double?

A

it is called generation time

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6
Q

what are the two terms that we use in a bacterial growth in a lab and define what they mean

A

culture and inoculation

culture= microbes growing in a medium
inoculation: introducing microbes into a medium to start a culture

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7
Q

define what batch culture mean

A

it is a closed system, once it is started there are no other nutrients that could be added, when nutrients are used up-bacteria stop growing

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8
Q

define what continuous culture mean

A

it is an open system, nutrients are continuously added, wastes are continuously removed, this supports indefinite growth

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9
Q

name the growth curve in batch culture

A

lag phase
exponential phase
stationary phase
death phase
phase of prolonged decline

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10
Q

define what exponential phase and the other term for it.

A

another term is log phase, and it is a the period of maximal production-cells numbers increase exponentially, this is used to calculate generation time.

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11
Q

define what lag phase is.

A

this is how bacteria will grow in batch culture, slow and steady. A period of adaptation (may take some time so they can start binary efficient).

Cells adjust to new media and get ready to grow

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12
Q

define what the term death phase is.

A

toxic waste products have accumulated(gathered), in visuals (decreased rapidly .)
the cells die at a uniform rate

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13
Q

define what the phase of prolonged decline is.

A

sometimes a small fraction of population survives the death phase, they may consume nutrients released from dying cells
- selects for the strongest cells in the population

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14
Q

define what stationary phase is

A

cells have reached maximal population density
nutrients have bee used up, waste have accumulated and no increase in cell number.

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15
Q

environmental factors that influence bacterial growth:
temperature requirements:
Define if it true or false.
Each species of microbe has its own specific temperature range, and this range usually spans abut 30 degrees.

A

true

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16
Q

define the following terms: What do they mean?

minimum
optimum
maximum

A

minimum - lowest temp supporting growth
optimum-temperature that supports best growth
maximum-highest temp supporting growth

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17
Q

what’s the temperature that supports the best growth?

A

optimum

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18
Q

bacteria can be grouped based on temperature range name the following terms

A

psychrophiles
psychrotrophs
mesophiles
thermophiles
hyperthermophiles

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19
Q

define what mesophiles are. also include its
min
max
optimum

A

moderate temperature loving, they are the ones that causes disease , and our body temp is 37, most bacteria are mesophiles, and most pathogens have temp optimum of 37 degrees

min= about 10 degrees
max: about 45 degrees
optimum = 25-45

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20
Q

define what psychrophiles are.

A

cold loving and grow between -5 and about 15c , they are killed at 20 degrees.

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21
Q

what are psychrotrophs?

A

have a very broad temp range
min is about -5
max is about 30-45
optimum is 15-30
these are the microbes that cause food to spoil in your fridge

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22
Q

define what thermophiles are

A

heating loving, and the min is about 40 degrees, and the max is 80 and the optimum is about 65.

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23
Q

what are hyperthermophiles , include the min, max, and optimum.

A

restricted to very few places on earth where water reaches these temperatures , an example would be deep ocean vents, min is 75 and the max is up to 121.

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24
Q

this involves the use of both hot and cold temperatures

A

food safety both involve the hot and cot temperature

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25
Q

heat is used to kill ____ and ____ microbes such as cooking.

A

mesophilic, and pyschrotophic

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26
Q

what temperature is used to slow growth?

A

cold temperature, and only psychroprophs will grow in refrigerator and slowly.

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27
Q

oxygen can be toxic to other and only requirement by some organisms.

A

true

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28
Q

define what obligate aerobes

A

require 02 for respiration (energy genration)

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29
Q

define what facultative anaerobes

A

can use for 02 for respiration but can also grow in its absence.

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30
Q

define what obligate anaerobes mean

A

cannot use 02 and are killed by it

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31
Q

define what microaerophiles mean.

A

require 02 in low amounts, but killed by high concetrations.

32
Q

define what aerotolerant anaerobes

A

cannot use 02, but are not killed by it.

33
Q

most bacteria grow at or near neutral pH

A

6.5-7.5

34
Q

bacteria that grow at very low pH:

A

acidophiles

35
Q

bacteria that grow at high pH:

A

alkaliphiles

36
Q

define osmosis

A

osmosis is the movement of solvent molecules across a semi-permeable barrier

37
Q

water will move from area of high concentration to area low concentration

A

osmotic pressure

38
Q

what is a hypertonic solution (name the characteristics)

A

high solute concentration , example: salt or sugar and water flows out of the cell and cell dries up we call that plasmolysis

39
Q

what is a hypotonic solution? name the characteristics

A

low solute concentration, water flows into the cell and cell bursts-osmotic lysis

40
Q

condition where solute concentration on outside of cell is equal to that inside the cell.

A

isotonic solution

41
Q

true or false.
Osmotic pressure is important in food preservation. Name some examples

A

true, an example would be fish, honey, salted

42
Q

some bacteria have adapted to life salt concentrations -requiring up to 30% NaCl. These bacteria are termed :

A

extreme halophiles for example : bacteria that live in dead sea

43
Q

blood has a concentration of about 0.9%, and does not inhibit the growth of most microorganisms. True or false?

A

true

44
Q

what are the nutritional that influence growth

A
  1. carbon
    2.nitrogen, sulfur, and phosphorus
    3.trace elements
    4.energy
45
Q

this is required for all organic molecules-backbone living matter

A

carbon

46
Q

what is heterotrophs?

A

take carbon for organic matter (ex would be sugars)

47
Q

what is autotrophs?

A

use inorganic carbon (i.e C02)

48
Q

this is required in smaller amounts for synthesis of cellular material

A

nitrogen, phosphurus, sulfur
example: protein, nucleic acids, phospholipids, ATP

49
Q

organisms need energy to build cell material and drive cellular processes

A

energy

50
Q

required in very small amounts and this is essential to the function of certian enzymes

A

trace elements such as iron, zinc, and molybdenum

51
Q

chemotrophs define it

A

acquire energy from chemical compounds, it may be organic or inorganic and example would be sugars

52
Q

are organisms classified based on how they obtain their carbon and energy

A

yes

53
Q

define what photoautotrophs are, what is their source?
and what do they include?

A

uses sunlight for energy
C02 as carbon source process called photosynthesis
includes– some bacteria like algae and plants

54
Q

what is photoheterotrophs?

A

use sunlight for energy, obtain organic carbon from food and some bacteria

55
Q

chemoautotrophs define it.

A

obtain energy from inorganic chemicals example for h2, h2s and uses co2 as carbon source and only done by some bacteria

56
Q

define what chemoheterotrophs

A

obtain energy from organic chemicals, use the same organic chemicals as their source of carbon.

All animals,fungi, protoza and most bacteria, all medically reolevant bacteria are chemoheterotrophs because they cause disease in us

57
Q

Culture media:
Solid media (Agar petri plates), how are they made?

A

made by adding agar (solidifying agent) to liquid bacteria , cannot be degraded by most bacteria

58
Q

does solid media allow growth of colonies ?

A

yes

59
Q

solid media allows growth of colonies:
- a genetically identical population of cells, and allow the isolation of pure cultures

A

all true

60
Q

what can culture media be?

A

1) chemically defined
2) chemically undefined

61
Q

define what chemical defined mean.

A

the exact chemical composition of the medium is known
example : media made from known quantities of salts and sugars

this is also known as minimal media

62
Q

define what chemical undefined mean.

A

contains rich organic ingredients (so the chemical composition is not known)
- also known as complex media
example : media containing yeast extract

63
Q

define selective media

A

prevent the growth of unwanted organisms ,allowing only the desired microbes to grow

64
Q

what inhibits the growth of all gram positive and most gram negative bacteria

A

selective media

65
Q

define differential media

A

used to distinguish different bacteria

66
Q

this can grow– but colonies of certain bacteria look different on the plate

give an example

A

differential media

ex: blood agar plates

67
Q

used to distinguish bacteria that can lyse(and eat) red blood cells name the example.

A

streptococcus pyogenes

68
Q

Counting bacteria :
Direct count
cells are counted by using what ?

A

by using a light microscope

69
Q

this usually employs a special counting chamber and inaccurate because it counts both live and dead cells

A

counting bacteria (direct count)

70
Q

Viable counts

A

only live cells are counted

71
Q

a liquid culture is diluted and plated onto agar plates to grow colonies

A

viable count

72
Q

each colony on a plate represents a single cell from the original culture

A

viable counts

73
Q

are colonies are counted, and used to calculate the # of bacteria in the original culture

A

viable counts

74
Q

what are counts aways expressed as ? and what are they called ?

A

expressed as cfu per mL and they are forming units

75
Q

assumption is that 1cfu=

A

1 live bacterial cell

76
Q

what does phototrophs mean?

A

harvest energy from the sunlight

microbiology (27 decks)

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