test two lec 8 Flashcards

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1
Q

for detailed studies of microbes they need to be grown separately in a….

A

pure culture

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2
Q

how many organisms have we cultured

A

.1%

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3
Q

what are the two main types of culture media

A

liquid or broth medium
solid medium
anaerobes use slant tubes

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4
Q

what are the two ways to isolate pure cultures

A

dilution streaking

spread plate technique

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5
Q

what is dilution streaking

A

dragging loop across the surface of an agar plate

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6
Q

what is spread plate technique

A

serial dilutions are performed on a liquid culture

a small amount of each dilution is then plated

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7
Q

early dilution of spread plate technique show

A

confluent growth

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8
Q

what is important about spread plate technique

A

viable bacteria produced and used to replicate

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9
Q

what does viable bacteria mean

A

one that successfully replicates to form a colony

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10
Q

what do we call organisms that metabolize but don’t replicate

A

viable but non culturable

maybe didnt find proper plate conditions

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11
Q

what is a complex media

A

bacterial growth solution that is nutrient rich but poorly defined
difficult to characterize metabolism of an organism

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12
Q

what is enriched medium

A

complex medium plus additional components
such as blood
helps mimic host environment

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13
Q

what kind of nutrients are found in complex media

A
yeast extract
beef extract
amino acids
peptides
nucleosides
vitamins
some sugars
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14
Q

what is synthetic media

A

bacterial growth solution that contains defined known components

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15
Q

why use synthetic media

A

used to study metabolic needs of different types of organisms

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16
Q

what are some components in synthetic media

A

H2O
various salts
C, N
energy sources

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17
Q

what is selective media

A

favor the growth of one organism over another

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18
Q

example of selective media

A

medium containing bile salts and crystal violet favors growth of gram neg over pos

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19
Q

what is differential media

A

exploit differences between two species that grow equally well, but differ in some biochemical aspect

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20
Q

example of differential media

A

e coli and salmonella
both gram neg
e coli ferment lactose which lower ph and changes dye of med to red

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21
Q

what is a macconkey medium

A

both selective and differential
selects gram neg due to bile salts and crystal violet
includes lactose, ferment and turn red
non fermenting is white

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22
Q

what is a petroff hausser counting chamber

A

microorganisms can be counted directly by placing dilutions on a special microscope slide
hemocytometer

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23
Q

what does propidium iodide do in fluorescence microscopy

A

cant penetrate membrane of living cells

only dead cells are stained red

24
Q

what does syto-9 do in fluorescence microscopy

A

penetrates both living and dead cells

green color

25
Q

what does acriding orange do in fluorescence microscopy

A

intercalates between DNA and RNA bases
DNA is green
RNA is orange
can see live and dead

26
Q

what does DAPI do in fluorescence microscopy

A

binds strongly to A-T rich regions in DNA; penetrates both living and dead cells

27
Q

what is fluorescence activate cell sorters

A

fluorescent cells are passed through a small orifice and then past a laser
detectors measure light scatter in the forward direction and to the side

28
Q

what is coulter counter

A

culture is forced through a small orifice, through which flows and electric counter
electrodes placed on both sides measure resistance
every time a cell passes through the orifice, the electrical resistance increases and the cell is counted
works best for EUK cells

29
Q

how can viable counts be counted

A

pour plate method

30
Q

what is the pour plate method

A

dilutions of liquid culture are placed directly onto a petri dish and then cooled liquid agar is added or the dilutions are needed to liquid agar is added or the dilutions are added to liquid agar and cooled then subsequently poured into an empty petri plate where the agar continues to cool and solidify

31
Q

what is pour plate method used to find

A

pathogens bc survive temps

32
Q

whats another way to find viable counts

A

counted indirectly by biochemical assays of cell mass, protein content, or metabolic rate

33
Q

why is biochemical assays not used in viable counts

A

can still have dead cells contributing to count

34
Q

what is optical density measuring

A

used to measure viable counts
a measure of how many particles are suspended in solution, based on light scattering by the suspended particles, still show dead cells

35
Q

most bacteria divide by

A

binary fission

36
Q

how does binary fission work

A

expansion of nucleoid as DNA replicates
creates equatorial septum
one parent cell splits into 2 equal daughter cells

37
Q

can cell division be asymmetric

A

yes, Hyphomicrobium
divide by budding
stalked parent and flagellum daughter

38
Q

what is exponential growth

A

growth rate, or the rate increase in population number or biomass, is proportional to the population size at a given time

39
Q

what kind of slope does an exponential curve have

A

continually increase

40
Q

what is generation time

A

time it takes for a population to double

41
Q

when does exponential growth occur

A

short periods of time when all nutrients are in full supply and toxic waste products have not become a limiting factor

42
Q

does exponential growth last indefinitely

A

no

43
Q

what is a batch culture

A

a liquid medium within a closed system
no fresh medium added
model effects changing environment

44
Q

what is lag phase

A

period of cell culture occuring right after inoclulation into new media, slow growth or no growth
cells need time to detect environment, express specific genes, synthesize components

45
Q

what is early log phase (exponential phase)

A

bacteria grow exponentially at their maximal possible rate

46
Q

explain bacterial cells in exponential phase

A

cell are largest
linear part of curve
cell components synthesized at constant rates relative to each other

47
Q

what is nutritional down shift and upshift

A

down: move cells to poor C source
up: move cells to better C source

48
Q

what is late log phase

A

as cell density increases, the rate of doubling eventually slows and a new set of growth phase-dependent genes is expressed
top of curve

49
Q

what is stationary phase

A

period of cell culture, following exponential phase, during which there is no net increase in replication
rate of cell division equals rate of cell death

50
Q

how do some cells respond to to stationary phase

A

turn into spores
decrease in size
minimize nutrient need
produce stress resistance enzymes

51
Q

what is death phase

A

period of cell culture following stationary phase in which bacteria die faster that they replicate
negative exponential function
can be prolonged

52
Q

what is continuous culture

A

fresh medium continuously added to a culture, and equally amount of culture is taken away

53
Q

what is a chemostat

A

continous culture system in which the diluting medium contains a limiting amount of an essential nutrient

54
Q

what is the point of chemostat

A

ensures logarithmic growth

growth rate directly related to dilution rate

55
Q

what is a washout

A

at faster and faster flow rates, cells are eventually removed more quickly that they can be replenished via replication so cell density decreases