Culturing Microbes

Question 1

what is a microbial cell made of

Answer 1

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

Question 1

chemical components of microbial cell

Answer 1

-CHONPS
-HOPS can come from organic molecules

Question 2

Mg 2+ role in microbial cells

Answer 2

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

Question 3

growth media or culture media

Answer 3

-can be highly varibale depending on microbe

Question 4

defined media

Answer 4

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

Question 5

complex media

Answer 5

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

Question 6

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

Answer 6

-microbes living in nutrient poor environments

-certain flexible microbes that adapt to many different environments

Question 7

microbes that require a great number of growth factors

Answer 7

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

Question 8

auxotrophy

Answer 8

-inability to produce a molecule you need for gorwth

Question 9

what is ecoli grown on

Answer 9

-simple concotion
-grown on complex media

Question 10

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

Answer 10

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

Question 11

selective media

Answer 11

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

Question 12

enrichment culture

Answer 12

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

Question 13

differential media

Answer 13

-contwan some sort of indicator when particular organisms are present

Question 14

what are solid plates most useful for

Answer 14

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

Question 15

what should liquid cultures geenrally be started using

Answer 15

-isolated single colonies from agar plates

Question 16

great plate count anomoly

Answer 16

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

Question 17

why can we not culture the majority of microbes in isolation

Answer 17

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

Question 18

direct count

Answer 18

-cells in the sample are counted using a microscope

Question 19

viable plate counts

Answer 19

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

Question 20

turbidimetric

Answer 20

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

Question 21

other indirect methods of counting mircobial cells

Answer 21

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

Question 22

how does direct microscope counting work

Answer 22

-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

Question 23

how does viable plate counts work

Answer 23

-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

Question 24

how does turbidity measurements work

Answer 24

-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

Question 25

microbial growth definition

Answer 25

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

Question 26

generation time

Answer 26

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

Question 27

batch cultures

Answer 27

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

Question 28

continous cultures

Answer 28

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

Question 29

lag phase in batch cultures

Answer 29

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

Question 30

exponential phase in batch cultures

Answer 30

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

Question 31

stationary phase

Answer 31

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

Question 32

decline phase

Answer 32

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

Question 33

generation time equation

Answer 33

-growth time/number of generations

Question 34

total number of cells at any given time equation

Answer 34

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

Question 35

biofilm formation

Answer 35

-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

Question 36

sessile growth vs planktonic growth

Answer 36

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

Question 37

formation of biofilms

Answer 37

-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

Question 38

how does cells change their programing during biofilm formation

Answer 38

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