6. microbial growth/control

binary fission

prok: 1 → 2

mitosis

euk: 1 → 2

discrete colony

cell aggr.

autotrophs

use inorganic source of carbon (co2)he

heterotrophs

catabolize reduced org. molcs

chemotrophs

energy from redox rxns w/ in/organics molcs

phototrophs

light

effect of temp on membs (w/ lipids)

low: rigid & fragile. high: fluid, oozy

neutrophiles

bact + protozoa, 6.5-7.5 ph

acidophiles

bact + fungi, acidic env

alkalinophiles

alk soils & water, up to 11.5 ph

hypertonic

plasmolysis → shrink

hypotonic

lysis → bursts

halophiles

9%+ nacl concen for cell wall support

extreme halophile

35% nacl

facultative halophiles

dont need high salt can tolerate

singlet oxy *O₂

higher state electrons

superoxide rads O₂^{. -}

anaerobes die if not detox, form during incomplete reduction of oxy in resp. anaerobes make SOD to detox

peroxide anion (o₂^2-)

formed during SOD rxns. aerobes have catalse/peroxidate to detox. obligate anerobes have insuff enzymes to treat.

hydorxyl radical (^.OH^-)

from ionizing radiation/incomplete hydrogen peroxide rxn. most reactive. doesn’t harm aerobes bc of catalase/peroxidase

superoxide dismutase (sod)

2 superoxide + 2 H⁺ → h2o2 (hyd peroxide) & o2

catalse

2 h2o2 → 2 h2o + o2

peroxidase

h2o2 + 2H⁺ → 2 h2o

aerobe response to oxy

aero resp

anaerobe response to oxy

dont use aerobic metab

facultative anaerobes

ferment, an/aerobic resp

aerotolerant anaerobe

dont aero metab, but its enzymes detox oxy

microaerophile

aerobes that need 2-10% oxy lvl, limited ability to detox h2o2 and superoxide rads

growth time

20-30 min for pop to double

growth phases

lag, stationary, death

measuring bact methods

direct count, viable count, biomass, indirect

counting chambers (direct count)

overcount bc cant distinguish dead/alive

viable count methods

plate count, filtration, most prob number (mpn)

plate count

ideally use 20-200 colonies

filtration

for extremely diluted, need large vol

indirect count

metab activity, dry weight, turbidity (cloudiness)

typ diff media

blood agar

typ selective + differential

MacConkey agar: inhibits gram pos, detects lactose ferm

bacterial control methods

sterilization, commercial sterilization, disinfection, antisepsis, sanitization, biocide, bacteriostasis, antimicrobial

sterilization

destroys everything

commercial botulism

kills botulism

disinfection

destroys harmfuls

antisepsis

destroys harmfuls from live tissue

sanitization

reduces microrganisms on utensils for safe lvls

bacteriostasis

inhibits microbes

antimicrobial modes

memb perm, dmg to proteins/nucleic acids

therm death pt (tdp)

lowest temp to kill all in 10 min

thermal death time (Tdt)

lowest time to kill all at specific temp

decimal reduction time (drt)

minutes to kill 90% of population

moist heat

pasteurization, autoclave

pasteurization

reduces spoilable organisms/pathogens. 63 C for 30 min. high temp short time (htst): 72 C for 15s. ultra high temp (uht): 140 c for 4s

autoclave

flowing steam, 121 C at 15 psi for 25 min, kills all organisms/endospores, touch surface

dry heat

kills thru oxidation: flame, incinerate, hot air sterilization

filtration

HEPA for >0.3 micrometers, memb filters > 0.22 micrometers

bacteriostatic - low tmp

fridge, deep freeze, lyophilization (freeze dry)

DESSICATION

no water → no metab

ionizing radiation (x ray, gamma ray, e beams)

ionize water → reactive oxy, mutate DNA

nonionizing radiation

UV rays dmg dna

microwaves

kill heat, but not microbes

phenol/phenolics

dmg & leak membs

halgens - iodine

alters protein synthesis & memb. tincture: alc solution. iodophore: combined with org molcs

halgens - chlorine

oxidizing that shuts down enzyme. bleach, chloramine

alcohol

denature protein, dissolve lipids, dont effect endospores/viruses, need water

heavy metals

oligodynamic action (tiny amt → antimicrobial), denature. ag, hg, cu, zn

surface active agents

soap - degerm, emuls. sanitizers - anions react with memb. quats (quat ammonium compounds) - kill bact, denature protein, disrupt memb