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test two lec 8 Flashcards

(55 cards)

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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

Study These Flashcards
A

cant penetrate membrane of living cells

only dead cells are stained red

24
Q

what does syto-9 do in fluorescence microscopy

Study These Flashcards
A

penetrates both living and dead cells

green color

25
what does acriding orange do in fluorescence microscopy
intercalates between DNA and RNA bases DNA is green RNA is orange can see live and dead
26
what does DAPI do in fluorescence microscopy
binds strongly to A-T rich regions in DNA; penetrates both living and dead cells
27
what is fluorescence activate cell sorters
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
what is coulter counter
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
how can viable counts be counted
pour plate method
30
what is the pour plate method
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
what is pour plate method used to find
pathogens bc survive temps
32
whats another way to find viable counts
counted indirectly by biochemical assays of cell mass, protein content, or metabolic rate
33
why is biochemical assays not used in viable counts
can still have dead cells contributing to count
34
what is optical density measuring
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
most bacteria divide by
binary fission
36
how does binary fission work
expansion of nucleoid as DNA replicates creates equatorial septum one parent cell splits into 2 equal daughter cells
37
can cell division be asymmetric
yes, Hyphomicrobium divide by budding stalked parent and flagellum daughter
38
what is exponential growth
growth rate, or the rate increase in population number or biomass, is proportional to the population size at a given time
39
what kind of slope does an exponential curve have
continually increase
40
what is generation time
time it takes for a population to double
41
when does exponential growth occur
short periods of time when all nutrients are in full supply and toxic waste products have not become a limiting factor
42
does exponential growth last indefinitely
no
43
what is a batch culture
a liquid medium within a closed system no fresh medium added model effects changing environment
44
what is lag phase
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
what is early log phase (exponential phase)
bacteria grow exponentially at their maximal possible rate
46
explain bacterial cells in exponential phase
cell are largest linear part of curve cell components synthesized at constant rates relative to each other
47
what is nutritional down shift and upshift
down: move cells to poor C source up: move cells to better C source
48
what is late log phase
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
what is stationary phase
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
how do some cells respond to to stationary phase
turn into spores decrease in size minimize nutrient need produce stress resistance enzymes
51
what is death phase
period of cell culture following stationary phase in which bacteria die faster that they replicate negative exponential function can be prolonged
52
what is continuous culture
fresh medium continuously added to a culture, and equally amount of culture is taken away
53
what is a chemostat
continous culture system in which the diluting medium contains a limiting amount of an essential nutrient
54
what is the point of chemostat
ensures logarithmic growth | growth rate directly related to dilution rate
55
what is a washout
at faster and faster flow rates, cells are eventually removed more quickly that they can be replenished via replication so cell density decreases

Microbiology (16 decks)

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