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MICRB 265 > Culturing Microbes > Flashcards

Culturing Microbes Flashcards

1
Q

what is a microbial cell made of

A

-55% protein
-25% nucleic acid
-lipid
-polysaccharide

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1
Q

chemical components of microbial cell

A

-CHONPS
-HOPS can come from organic molecules

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2
Q

Mg 2+ role in microbial cells

A

-key role in stabalizing negative charges in membranes
-also used by enzymes

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3
Q

growth media or culture media

A

-can be highly varibale depending on microbe

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4
Q

defined media

A

-media prepared by adding precise/known quantities of chemicals to water
-know the exact composition
-know what your working with

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5
Q

complex media

A

-contains extracts or digested organic material with unknown composition
-cheaper easier and work for a broader arrray of different microbes

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6
Q

What microbes can make most or al of the organic molecules they need from a few basics

A

-microbes living in nutrient poor environments

-certain flexible microbes that adapt to many different environments

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7
Q

microbes that require a great number of growth factors

A

-many organisms that have olbigate symbiotic lifestyle
-organiss that live in nutrient rich environemtns such as LAB

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8
Q

auxotrophy

A

-inability to produce a molecule you need for gorwth

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9
Q

what is ecoli grown on

A

-simple concotion
-grown on complex media

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10
Q

what is lactic acid bacterium, l.mesentheroides, need to grow

A

-requires a number of organic building blocks such as AA and vitamins

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11
Q

selective media

A

-used to isolate a limited assortment of microbes
-combination of positive selection and negative selection

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12
Q

enrichment culture

A

-similar to selective media but less selective and richer media
-promotes geowth to increase cell numbers of particular microbes from samples
-usually somewhat selective

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13
Q

differential media

A

-contwan some sort of indicator when particular organisms are present

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14
Q

what are solid plates most useful for

A

-usefule for isolating single colonies
-ideally single colony oiginates from single cell that grows to large numbers and can be readily seen

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15
Q

what should liquid cultures geenrally be started using

A

-isolated single colonies from agar plates

16
Q

great plate count anomoly

A

-when environmental samples are plated on generic growth plates meant to be non-selective, >99% of the microbes dont grow

17
Q

why can we not culture the majority of microbes in isolation

A

-syntrophy`- microbes feeding off one another, metabolismintegrated between multiple different species

18
Q

direct count

A

-cells in the sample are counted using a microscope

19
Q

viable plate counts

A

-a small sample of cells are spread on agar plates and incubated - colonies counted

20
Q

turbidimetric

A

-absorbance of light by a microbe growing in a lqiuid culture is measured in a spectrophotometer

21
Q

other indirect methods of counting mircobial cells

A

-O2 consumption, CO2 production, metabolic activity
-Quantitative PCR to determine the number or genome equivalents

22
Q

how does direct microscope counting work

A

-known volume added to gridded microscope slide/coverslip and cells are counted under microscope
-doesnt require growth but is laborious and prone to inaccuracies and you likely need to stain microbes
-hard to differentiate between viable and dead cells

23
Q

how does viable plate counts work

A

-common and reliable
-have to know how to grow microbes
-assumes colonies emerge from single cell
-assumes all cells will grow to form colony, though some cells can be viable but none culturable under plating conditions

24
Q

how does turbidity measurements work

A

-microbes catter light and amount of light scattered proprotional to number microbes in a liquid sample
-very common
-need to find correlation between optical density at chosen wavelength and cell numbers
-only works in pure cultures and liquid cultures
-limited concentration range
-not labour intensive and growth can be continuosly or regularly measured over time
-growth can be visually oserved
-need right amount of cell numbers (not too low and not too high_
-time on X axis and OD on Y axis

25
Q

microbial growth definition

A

-refers to increase in population size
-cell division resulting in multiplying in numbers

26
Q

generation time

A

-the amount of time it takes for one cell to become two
-varies greatly depending on mcirobe and growth conditions

27
Q

batch cultures

A

-cultures in a fixed volume in a closed contained like a flask or test. tube

28
Q

continous cultures

A

-cultures within systems where waste product are being removed and new media fed in

29
Q

lag phase in batch cultures

A

-period of slow or no growth
-,icrobes adjust to new environment
-length of this phase varies
-bigger adjustments = longer lag phase

30
Q

exponential phase in batch cultures

A

-growin population doubles at regular intervals
-nutrients not yet exhausted waste products not slowing growth

31
Q

stationary phase

A

-nutrients begin to be exhaustedand or accumulating waste products inhibit growth
-little to no net growth, still some growth and death

32
Q

decline phase

A

-cells start to die if left long enough
-net decline in celel numbers
-this phase isnt all relevant

33
Q

generation time equation

A

-growth time/number of generations

34
Q

total number of cells at any given time equation

A

-Nt =N0 x2^n
-Nt = total number of cells
-N0 = starting number of cells
-2^n = number of generations

35
Q

biofilm formation

A

-sessile growth can develop into biofilms
-cells encased in matrix attached to surface
-matrix is often polysacchardies but can also include protein and DNA
-many times it a complex community with complex cellular differentiation
-cells with different properties in different layers of biofilm

36
Q

sessile growth vs planktonic growth

A

-sessile - growth on surface
-planktonic growth - free living organisms in liquid

37
Q

formation of biofilms

A

-can start with planktonic cells attaching to a surface via appendages such as pili, fimbriae or even flagellum
-colonization begins and cells multiply and produce extracellular polymers such as polysaccharides to hold matrix together
-during decelopment, cells biological programs change
-cells with begin to disperse an resume planktonic state

38
Q

how does cells change their programing during biofilm formation

A

-express unqiue combinations and amounts of genes to facilitate this biofilm lifestyle
-different cells on different layers have different programs

MICRB 265 (31 decks)

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