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MICR221 > Module 1 (L1-5) > Flashcards

Module 1 (L1-5) Flashcards

1
Q

Describe binary fission

A

the cell elongates and the chromosomal DNA is replicated. Chromosome migrates to the end of each cell, cross wall (septum) forms and then the cells separate

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2
Q

what is the mean generation time

A

the time it takes for one cell to divide (the whole population)

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3
Q

what determines the shape of the bacterial cell

A

the shape depends on the plane of division during binary fission

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4
Q

how does having a small surface area benefit a cell

A

because the SA to volume ratio is increased so the uptake of nutrients is increased hence a larger growth rate

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5
Q

does a rod or cocci cell have a greater surface area?

A

a rod

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6
Q

require molecular oxygen for aerobic respiration

A

aerobes

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7
Q

prefer the absence of oxygen and carry out anaerobic respiration or fermentation

A

anaerobes

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8
Q

what is the final electron acceptor in the electron chain in aerobic respiration

A

oxygen or some other oxidant

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9
Q

what is the final electron acceptor in anaerobic respiration

A

an exogenous molecule eg nitrate or sulphate

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10
Q

how is ATP synthesized in fermentation and what is the final electron acceptor?

A

ATP is synthesized via substrate-level phosphorylation and the electron acceptor is endogenous eg pyruvate

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11
Q

describe the ways that organisms are classified based on their requirements for carbon, energy and electrons

A

phototrophs, chemotrophs, lithotrophs, organotrophs, heterotrophs, autotrophs

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12
Q

how does temperature affect microbial growth?

A

minimum - things happen slowly
optimum - most efficient
maximum - cell dies

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13
Q

what are the physical factors for growth requirement?

A

gaseous atmosphere, temperature, pH, osmotic pressure

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14
Q

what are the chemical factors that affect growth ?

A

water and energy and electron source

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15
Q

whart are the 2 categories according to energy source?

A

phototrophs, chemotrophs

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16
Q

phototroph

A

derive energy from sunlight

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17
Q

chemotroph

A

derive energy from the oxidation of chemical compounds

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18
Q

what are the 2 categories for the electron source

A

lithotrophs, organotrophs

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19
Q

lithotroph

A

the carbon source is from reduced inorganic substances

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20
Q

organotrophs

A

the carbon source is from reduced organic compounds

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21
Q

what are the 2 categories for carbon source

A

autotrophs, heterotrophs

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22
Q

autotrophs

A

utilise only inorganic carbon in the form of CO2

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23
Q

heterotrophs

A

utilise organic carbon (proteins, carbs, lipids)

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24
Q

how can oxygen be toxic

A

oxygen has to be converted by metabolic enzymes into highly reactive derivatives such as the superoxide free radical (O2-), which is very damaging to cells. Aerobes and most facultative organisms convert superoxide free radical to hydrogen peroxide by means of the chemical superoxide dismutase. This is further broken down by catalase or peroxidase. Anaerobes do not possess these enzymes and so cannot tolerate oxygen.

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25
Q

obligate aerobe

A

need oxygen and have SOD and catalase

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26
Q

facultative anaerobe

A

prefer oxygen and have SOD and catalase

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27
Q

aerotolerant anaerobe

A

tolerate oxygen and have SOD but no catalase

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28
Q

strict anaerobe

A

oxygen is toxic and have no SOD or catalase

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29
Q

mircoaerophile

A

2-10% oxygen and have SOD and catalase in low levels

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30
Q

name 5 types of bacteria based on their temperature preference

A

psychrophiles, psychrotrophs, mesophiles, thermophiles, hyperthermophiles

31
Q

what are the macroelements/macronutrients

A

carbon, nitrogen, hydrogen, oxygen, phosphorus, sulphur

plus the cations and anion

32
Q

what are the micronutrients

A

zinc, cobalt, molybdenum, copper, magnesium

33
Q

what is defined media

A

a type of culture media that is chemically defined, so we know ow the exact composition of every component and the amount in the media. it is made with specific chemicals and grows most chemoautotrophs and photoautotrophs

34
Q

what is complex media

A

a type of culture that is not chemically pure because we do not know the exact composition and it used complex source of nutrients such as glucose, beef extract, yeast extract and peptones which are digestive protein material. it grows most chemoheterotrophic organisms

35
Q

what is transport media

A

temporary storage to ensure viability but no growth, it only contains buffers and salts and lacks growth factors. it should be in the same condition as it was when it was taken from the patient

36
Q

what is enriched media?

A

general nutrient supplements added (generally encouraging). It is used to harvest as many different microbes as possible, if a microbe is fussy it should grow here.

37
Q

what is an enrichment birth

A

it is designed to increase the numbers of a desired microbe (specifically encouraging). It gives a competitive edge to the desired microbe, which then becomes the dominant species and is commonly used in the clinical laboratory

38
Q

what is selective media ?

A

suppresses unwanted microbes and encourages desired microbes (specifically inhibiting). being specifically inhibiting makes it different to enrichment

39
Q

what is an example of selective media?

A

mannitol salt agar which inhibits all except staphylococci, its selective for staphylococci

hekoen agar which inhibits gram-positive and some gram-negative (non-enteric) gram-negative bacteria, is selective for gram-negative enteric bacteria

40
Q

what is differential media

A

notice a color change. it contains indicators that visually distinguish between organisms, team up a carb with a pH indicator to show if acid has been produced

41
Q

what is an example of differential media ?

A

mannitol salt agar
mannitol fermented -> acid
mannitol fermenters change the agar colour from pink to yellow
pathogens non mannitol fermenters agar not changed

42
Q

explain how mannitol sodium chloride agar and hektoen agar are both selective and differential media

A

-

43
Q

explain how blood agar is an enriched and differential media

A

it is enriched to increase the growth of bacteria and inhibit some pathogens/bacteria and it is differential because the different zones of hemolysis is visually distinguishable, whether it be partial lysis of the RBC leading to a green discolorization or the complete lysis of the RBC producing a clear zone or a non-hemolytic zone

44
Q

describe the lag phase

A

when all the cells are not dividing, they begin to synthesize the components needed for binary fission, this phase can be shorter if everything is supplied

45
Q

describe the exponential/log phase

A

when the cells are actively dividing and it constantly increases, the slope reflects the rate of division

46
Q

describe the stationary phase

A

when all the nutrients have been used/something is all gone or the cell waste is toxic. the cell death is equal to cell division

47
Q

describe the death phase

A

it is exponentially decreasing because the cells can no longer reproduce, this indicated variance

48
Q

define continuous culture

A

it is an open system, the material is added and taken away to keep the bacteria growing in an exponential phase

49
Q

what is a primary metabolite

A

a kind of metabolite that is directly involved in normal growth, development and reproduction, it is essential for the growth of the microbe and is produced during the logarithmic phase

50
Q

what is a secondary metabolite

A

a metabolite that is not essential for growth and accumulates during the stationary phase

51
Q

what are the methods for measuring microbial growth

A

direct - microscopic observation
plate count - the viable cells
turbidity- the conc from absorbance

52
Q

what is the primary function of most endospores?

A

ensure survival of a bacterium through periods of environmental stress

53
Q

what are the 7 layer of an endospore ?

A

core, inner membrane, germ cell wall, cortex, outer membrane, coat, exosporium

54
Q

what is in the core of a endospore ?

A

normal cell structures, DNA, RNA

55
Q

what is the cortex of an endospore composed of ?

A

peptidoglycan

56
Q

what is dipicolinic acid?

A

a spore specific chemical that appears to help in the ability for endospores to maintain dormancy, it accounts for 10% of the endospores dry weight

57
Q

What is the physical determinants of resistance for endospores?

A

the coat is made up of thick layers and the inner membrane is impermeable

58
Q

what is the chemical (core) determinants of resistance for endospores?

A

there is a low water content (15% compared to >80% in vegetative cells), the pH is lower than that in vegetative cells and the high content of dipicolinic acid and the Ca+ that forms a lattice structure and stabilised DNA. Small acid soluble proteins that bind to DNA and slightly alter it to protect it

59
Q

what is the chemical (cortex) determinants of resistance for endospores?

A

the decreased peptidoglycan cross linking index (2.9% in endospore compared to 33% in vegetative cells), this is because this modified peptidoglycan wall is required for maintenance of spore coat dehydration and the accompanying metabolic dormancy and heat resistance

60
Q

what is endospore germination?

A

germination involves the dormant endospore starting metabolic activity and thus breaking hibernation. It is commonly characterized by rupture or absorption of the spore coat, swelling of the endospore, an increase in metabolic activity, and a loss of resistance to environmental stress

61
Q

what are the 3 steps of endospore germination?

A

activation, germination, and outgrow

62
Q

what is absolute sterilisation

A

complete removal or destruction of all microorganisms from inanimate objects, it is brought about by the use of physical of chemical methods and is non-selective

63
Q

what is disinfection

A

the removal of a infection, destruction or removal of a microorganism (but not bacteria endospore) on inanimate objects by physical or chemical means

64
Q

what is antisepsis

A

chemicals applies to body surfaced to destroy or inhibit growth of microorganisms within host tissues

65
Q

what items cannot be autoclaved?

A

toxic chemicals (phenol), heat-labile compounds (antibiotics) heat-sensitive equipment and some types of plastic

66
Q

what are examples of dry heat used for sterilization

A

flaming and incineration, hot air oven and freezing

67
Q

what tis the thermal death point?

A

the lowest temp required to kill all the cells in a standards suspension of bacteria in a liquid culture within a period of 10 minutes

68
Q

what is the thermal death time ?

A

the length of time required to kill all of the cells in a standard suspension of bacteria in liquid culture at a given temperature.

69
Q

What is the thermal reduction time?

A

the length of time taken to obtain a ten-fold reduction in the number of bacteria in a standard suspension of bacteria in liquid culture. A ten-fold difference is 90% killed (1 log difference)

70
Q

what is the Z value

A

the temp required for one log10 reduction in the D value.

71
Q

what is an example of a physical sterilization method

A

filtration

72
Q

what is the usual pore size for a filter ?

A

0.2 micrometers to filter out bacteria

73
Q

explain what a depth filter is

A

(eg HEPA) is a random array of overlapping fibers that are 5-7mm high. Particles get caught up in it and it works like a pre-filter because of its height they can capture lots of things. A disadvantage of using a depth filter is that there is no indefinite limitation, being heigh means that it will retain a level of the solution you pass through it. It is good at filtering air (HEPA- high efficiency particular air). HEPA sterilizes air.

MICR221 (1 decks)

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