Topic 3c: Growth Flashcards
what is a growth curve
dif than standard curve; exponential growth = # of cell db in constant time interval
what is generation time
g = t/n (n=# of gens)
what is division rate
v =1/g (aka mean growth rate)
what 4 phases can the growth curve be divided into
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
what happens to cells in death phase
-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)
what is a standard curve
counting col’s that grow; create rel bw dead and living
what is a continuous cult
-open system that replenishes and removes waste
-steady state//# of cells constant
-good for exps (keeps cells in log growth)
what is chemostat and why is it imp
-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 []
what is a direct count
-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
what is flow cytometry
-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
what are viable counts
-if in liq cult, can est MPN
–counting viable cells
-dis = undercount and bact asso’d w one another (ex. biofilm)
what are the 3 errors w plate counting
media and growing conditions
plating inconsistencies
direct counts usu yield more orgs than those recovered on plates
what is optical density and dry wt used for
-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
what happens to growth when hot
can inc growth but then gets too much and PMs lose cohesiveness (prots denature and cant grow)
psychrophile
likes cold, ocean water could be env (4)
mesophile
on/in 39
psychotolerant
opt growth near mesophile (37) but can tolerate low temp
thermophiles
like warm (60; atleast above 45)
-euks max at 65
hyperthermophiles
88 and 106; super hot, usu arch
–autoclave at 121 to sterilize
what do bact need to do in cold envs and what is a big challenge
-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
what are adaptations made to live in high temps
-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)
neutrophiles
most bact and protists
5.5-7.9
acidophiles
0-5.5
-most fungi
alkaliphiles
+8
most marine orgs
for all neuts, acido’s and alkal’s, internal ph usu 7, how?
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
notes ab water activity
-aw
-range 0-1 (pure water = 1)
-cytoplasm usu has higher [] of solutes than env
dif types of orgs for salt
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 []
hypo v hypertonic
hypo - more [] in
hyper - more [] out
how do microbes respond to osmotic changes
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)
dif types of oxygen species (5)
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
how is oxygen toxic and how do species deal w it
get reactive oxygen species which damage cells (byprod of resp)
–prod enz to break them down (catalase)
how do pressure and radiation affect cell growth
-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
what is a biofilm
-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
why form a biofilm
-form stable microconsortia
-biodiversity
-genetic exchange
-retain xtracell enz’s in matrix
-access to biodigradable matter
-recycling in nuts (retained)
-protection
-communication
how are biofilms formed
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)
