Topic 3c: Growth

Question 1

what is a growth curve

Answer 1

dif than standard curve; exponential growth = # of cell db in constant time interval

Question 2

what is generation time

Answer 2

g = t/n (n=# of gens)

Question 3

what is division rate

Answer 3

v =1/g (aka mean growth rate)

Question 4

what 4 phases can the growth curve be divided into

Answer 4

lag - dep on env/cult (if lots of nuts, very short)
exponential - rep going as fast as poss; most act cells & what researchers use
stationary - plateau (# cells dying/growing =); amnt of resources avail = less
death - slow & exponential

Question 5

what happens to cells in death phase

Answer 5

-could program cell death (feed on other cells)
-or viable but not culturable (may not grow but arent dead ////or dead but have intact mem that doesnt break open)

Question 6

what is a standard curve

Answer 6

counting col’s that grow; create rel bw dead and living

Question 7

what is a continuous cult

Answer 7

-open system that replenishes and removes waste
-steady state//# of cells constant
-good for exps (keeps cells in log growth)

Question 8

what is chemostat and why is it imp

Answer 8

-artificial rep of env w lots of nuts to have cells continually growing (reaches steady state)
-find balance w met capacity (cant divide any faster, so if add more nuts, will just hit wash out)
–inc dilution rate/flow rate, inc nuts for cells
–to get max amnt of cell growth/yield by nut []

Question 9

what is a direct count

Answer 9

-way to meas growth (phys counting)
-use counting chamber (grids) where each square has defined volume
-dis = cant tell if dead/alive (unless use viable cells) and cell types look “ unless using flu

Question 10

what is flow cytometry

Answer 10

-way to meas growth
-based on light scattering
-directly counts cells using coulter counter which is based on electrical flow (uses laser to detect and count)
-dis = cant tell if dead or alive (unless use viable strain), need special equip
-ad = faster than phys direct

Question 11

what are viable counts

Answer 11

-if in liq cult, can est MPN
–counting viable cells
-dis = undercount and bact asso’d w one another (ex. biofilm)

Question 12

what are the 3 errors w plate counting

Answer 12

media and growing conditions
plating inconsistencies
direct counts usu yield more orgs than those recovered on plates

Question 13

what is optical density and dry wt used for

Answer 13

-meas growth
-opt dens = more common and use spectro (based on scattering of light)
–creates OD readings (to det [] of cells)
Dis = each species refracts dif t/f need new stand curve; dead cells can scatter light; need prev created SC to know rel
Ad = fast and easy

Question 14

what happens to growth when hot

Answer 14

can inc growth but then gets too much and PMs lose cohesiveness (prots denature and cant grow)

Question 15

psychrophile

Answer 15

likes cold, ocean water could be env (4)

Question 16

mesophile

Answer 16

on/in 39

Question 17

psychotolerant

Answer 17

opt growth near mesophile (37) but can tolerate low temp

Question 18

thermophiles

Answer 18

like warm (60; atleast above 45)
-euks max at 65

Question 19

hyperthermophiles

Answer 19

88 and 106; super hot, usu arch
–autoclave at 121 to sterilize

Question 20

what do bact need to do in cold envs and what is a big challenge

Answer 20

-prots are less hydrophob/more flex; PM have more unsat to keep fluidity
-challenge = ice crystals (pop mem’s and break cells)
—sol = sugars as anti freeze

Question 21

what are adaptations made to live in high temps

Answer 21

-prots = heat stable (special solutes in cytosol)
-have enz’s to maintain strength and struct (mod’d aa)
-mem’s adapted to be more solid/stable (ether link bw polar head grp and FA chain); also have monolayer (t/f no layers to peal apart when warm)

Question 22

neutrophiles

Answer 22

most bact and protists
5.5-7.9

Question 23

acidophiles

Answer 23

0-5.5
-most fungi

Question 24

alkaliphiles

Answer 24

+8
most marine orgs

Question 25

for all neuts, acido’s and alkal’s, internal ph usu 7, how?

Answer 25

neu - K+/H+ antiporter exchanger, express acid tol prots, ATPase pump, acid shock/heat shock prots

acido’s - transport cations into cell or have proton transporters move H+ out and highly impermeable cell mems

alkal’s - Na+ (not H+) to fuel transport and motility

Question 26

notes ab water activity

Answer 26

-aw
-range 0-1 (pure water = 1)
-cytoplasm usu has higher [] of solutes than env

Question 27

dif types of orgs for salt

Answer 27

non halophile - dont like salt
halotolerant - can survive salt but dont thrive
halophile - loves salt
extreme halophile - survive in high [] salt (+30%)

osmophiles - survive in high sugar []

Question 28

hypo v hypertonic

Answer 28

hypo - more [] in
hyper - more [] out

Question 29

how do microbes respond to osmotic changes

Answer 29

1) mechanosensitive channels allow release of water (if lots water coming into cell)
2) Compatible solutes (sugars, alc’s aa deriv which inc solute [] inside selves)

Question 30

dif types of oxygen species (5)

Answer 30

aeortolerant - dont req O2 but can tolerate it
microaerophile - just below surface
aerobe - grow at surface
fac anaer - throughout tube, pref O2
anaerobes - grow away from surface

Question 31

how is oxygen toxic and how do species deal w it

Answer 31

get reactive oxygen species which damage cells (byprod of resp)
–prod enz to break them down (catalase)

Question 32

how do pressure and radiation affect cell growth

Answer 32

-affect mem fluidity and funct
-get increased unsat’d FA
-rad kills via dna damage
—-to repair, have donut shape as phys adaptation to keep it close together

Question 33

what is a biofilm

Answer 33

-xtracell polymeric substance
-made most of carbs, some dna (may help w adherence/formation; has role in evading immune sys, binding cations)
-many species of bact
-adherent

Question 34

why form a biofilm

Answer 34

-form stable microconsortia
-biodiversity
-genetic exchange
-retain xtracell enz’s in matrix
-access to biodigradable matter
-recycling in nuts (retained)
-protection
-communication

Question 35

how are biofilms formed

Answer 35

attach (motile cells become non motile and adhere to suitable surface)
colonize (commun and form polysac)
develop (other orgs join)
active dispersal (some cells released to find new location)