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90 terms

MICR221 Module 2

increase no. population
through binary fission
1 parent--> 2 daughter cells --> cetc
rod and cocci
mean generation time- time taken for one cell to divide e.g. E.coli= 20 mins
plane of division depends as cell arrangement
energy: phototrophs, chemoautotrophs
carbon: autotrophs, heterotrophs
oxidation of chemical compounds e.g. sugar
inorganic carbon of CO2
organic carbon-protein, lipids
physical factors for growth
gaseous atmosphere
osmotic pressue
chemical factors for growth
water 80-90%
energy- phototrophs, chemoautotrophs,
carbon- autotrophs, heterotrophs
nitrogen, phosphate, sulfur
obligate and facilitate aerobe
use superoxide dismatase, catalase
most aerotolerant anaerobes
use superoxide dismatatse, peroxidase
obligate anaerobes
use none
gaseous atmosphere
aerobe require O2= aerobic respiration, electron transport chain, final electron acceptor O2
anaerobes prefer absense of O2= anaerbic respiration-->use electron transport chain--> final electron acceptor exogenous, O2 toxic, or fermentation-->use no electron transport chain-->use ATP synthase by substrate level phosphorylation-->final electron acceptor= endogenous
anaerobic respiration
use electron transport chain
final electron acceptor, exogenous, O2 toxic
use no electron transport chain
use ATP synthase by substrate level phosphorylation
final electron acceptor= exogenous
obligate aerobe
needs O2
facultative anaerobe
prefer O2
grows with or without O2
aerotolerant anaerobe
tolerant O2
strict anaerobe
O2 toxic
super oxide radicals toxic
little O2
2-10% O2
increase CO2
need CO2
minimum-slow down
optimum-at peak
maiximum-denature, damage, cell death
-10 to -17 degrees
2 to 35 degrees
14 to 43 degrees
42 to 80 degrees
68 to 105 degrees
optimum pH for growth
netral 6-9 pH
acidophillic bacteria 1-3 pH
osmotic pressure
no of molecules the soln
hypertonic- increase conc-sugar h2o plasmolysis
hypotonic- decrease conc-increase cell size
loss of ability to multiply
complete killing or removal of all microorganisms- physical and chemcial
destruction of microorganism on inanimate objects by chemical means
reducing microbial load, inanimate objects to an acceptable level
thermal death pt
lowest temp required to kill all cells in 10 mins
thermal death time
length of time required to kill at a given temp
decimal reduction time
length of time taken to obtain ten-fold reduction
control methods using heat
boiling water
dry heat
batch pasteurisation
flash pasteurisation
ultra-heat treatment
boiling water
100 degrees
15 mins
kills cells
doesn't kill spores
121 degrees
15 mins
kills cells
kills spores
dry heat
160 degrees
kills cells
kills spores mostly
batch pasteurisation
63 degrees
30 mins
kills some cells
doesn't kill spores
flash pasteurisation
71 degrees
15 sec
kills some cells
doesn't kill spores
ultra-heat treatment
140 degrees
1 sec
kills cells
kills spores
methods of measuring growth
microscopy- glass slide, totvboial counts
Spectrometry- density, curve, total counts
Dilution series- Plate count, Viable
Growth is exponential and rapid
measuring growth
population-final no.= initial no x 2(power of n)
primary metabolite
essential for growth, logarithmic phase
secondary metabolite
not essential
accumulate during stationary phase
medias for growth
complex media
not know exact composition
contains energy and carbon
most microbes grow
defined media
know exact composition
know every component and amount
specific sugars, amino acids, vitamins
specific microbe
specialised media types
specialised enriched
transport media
temporary, storage, being transported
no microbial growth, no microbial death
buffers and salts- protective
lack carbon, nitrogen, organic factors
enrichment broth media
specifically encouraging
low no.
give competitive edge
clinical labs- faecal specimen
specialised enriched media
general nutrients
harvests many microbes
selective media
encourages growth of same organisms and inhibiting others
differential media
containing indicator to distinguish which organism
blood agar
enrichment and differential
alpha haemolysis- partial lysis RBC- green
beta haemolysis- complete- clear zone
gamma- no haemolysis
hektoen agar
lactose, sucrose, salicin, acid fuchsin, bromo blue
carbohydrate fermented-->acid (yellow/pink)= E.coli
non-fermenters--> blue/green and black colonies from H2S production= Shigella/Salmonella
mannitol salt agar
mainitol, phenol red
mannitol fermented-->acid yellow, pathogens e.g. Saiureus
non-mannitol fermentors-->no change e.g. S. epi
modified cell wall
pathogenic or non-pathogenic
vegetative-->binary= 8 hrs SPORALATION
indefinite survival time
endospore--> cell = 15 mins
endospore structure
core- DNA and ribosomes but metabolically inactive
cortex- peptidoglycan less cross-linked
spore coat- large several protein layers, impermeable, physical resistant, UV radiation and dessiccation PROTECTION
exosporidium- thin outer most layer, lipid, carbohydrate coat surrounds endospore `
resistance of endospore
1. physical spore coat
2. chemical
- low water content- 15%- gel-like substance= heat resistant, protective
-small acid-soluble proteins- bind DNA altering confirmation, protect from damage
-high content of dipicolinic acid and Ca2+ in core- lattice protein makes resistant
germination of endospore
1. activation- chemicals or heat
2. germination- breaking spore state, swell rupture, loss protection, increase metabolic activity
3. out growth- spore emerges out of coat, divides into active bacterial cell
filtration- control microbial growth
filter with pores too small for microorganisms, but large enough for liquies to pass through
pore size= 0.45um or 0.20um
use e.g. antibiotic, tissue culture mieda, serum, gases, filtered beer
depth filter
asbestos or glass
random array of fibers
particles trapped in fibers
no definite pore size
thick filter- 5mm high
retain some liquid- disadvantage
high dirt handling capacity
cope with alot of microbes
used as pre-filter- containment
membrane filter
cellulose acetate or nitrate
thin piece
pore size regular
like sieve, trap microbe at top
disadvantages: easily blocked by contaminants
therefore depth and membrane filter used
nucleopore filter
absolute pore
low flow rate
low no. of pores
not used often
used in prep for electron microscopy
(High Efficiency Particulate Air) filters
laminar flow hood (basic specimen protection)
class II biological safety cabinets (protection of specimen, you and environment from contamination)
radiation- control microbial growth
non-ionising radiation e.g. UV radiation
ionising radiation e.g. xrays
non-ionising radiation
wavelength of 260 nm damages DNA in cell forming pyrimidine diamers or direct protein damage
sterilise benches and air
not used on large volumes of liquids penetrate these in significant depth
gram -ve more insensitive-->+ve-->endospore
ionising radiation
xrays kills indirectly by inducing reactive chemical radicals (free radicals) by breaking individual moelcules into ions
0.3-0.4 millirads-generally kills microbes
>50 rads- human becomes ill from radiation
hydroxyl free radicals= strong oxidising agents
+ve= more penetrating-sterlise products for packaging
-ve= but expensive and need elaborate safety precautions
used to sterilise lab products (petri dishes), treatment of sewerage and industrial sludges, food preservation
SOS Repair System
bacteria possess repair enzymes which can repair damaged pyrimidine diamers
so UV will cause death of bacteria only if the damage incurred is greater then that which can be repaired
are chemical agents that kill or inhibit growth of microorganisms and that are sufficiently non-toxic to be applied to living tissues
included in pharmaceutical preparations to prevent microbial spoilage of product
conditions influencing effectiveness of antimicrobial agents
population size
properties of chemical agents
population composition
environmental factors
toxicity of agent
population size
only fraction of microorganisms die during certain time interval
one log decrease=90% of population killed
if rate of killing is same it will take longer to kill all members of a larger population than a smaller one
properties of chemical agents
population composition
- Phase of growth- exponential quickly die with chemicals
- Polymer or capsule production- tuberculosis waxy cell wall take a long time to kill
- Altered cell wall or membrane- reduce permeability to chemicals
- Modified sensitive sites- enzymes more resistant
- Cellular aggregation/biofilms- degree of protection
- Resistant structures- endospores- much more difficult to destroy
environmental factors
- Neutralisation by organic material- absorb or chemically inactivate chemical material- milk proteins blood fetal material
- Temperature- higher temperatures than lower temp
toxicity of agent
correct agent to correct microorganism
use and exposurer and environment
ideal characteristics of chemical control agents
high antimicrobial activity
broad spectrum
adequate soluability
minimum toxicity
detergent activity
minimum material effects
minimum inactivation by organic material
activity at ordinary temperatures
deoderising ability
low cost
high microbial activity
be able to kill microorganisms
broad spectrum
of antimicrobial activity
to be able to store for a long period of time, no loss of activity
do not want to settle out or sediment out
minimum toxicity
shouldn't harm environment, animals or humans
detergent activity
remove dirt action
minimum material effects
different surfaces shouldn't harm
activity at ordinary temperatures
do not need to heat up or cooled down at room temperature
deodourising ability
microbes smell a little bit
low cost
within market range