-
How long does it take an E.coli cell to multiply
it can divide every 20-30 minutes
-
essential nutrients
nutrients a microbe needs and cannot make itself so its environment supplies them
-
6 microorganisms needed macronutrients
C,N,P,H,O,S
-
macronutrients are needed and in large amounts while micro nutrients are needed but in very small amounts
-
6 micronutrients all cells need
Co, Cu, Mn, molybdenum, Ni, Zn
-
why are the micronutrients needed
the elements are essential components of enzymes and aid in the catalytic processes
-
breaking down molecules for energy
catabolism
-
using E to rebuild cell components, reduces entropy
anabolism
-
central biochemical pathways used for the balance between catabolism and anabolism
metabolism
-
3 examples of metabolism
TCA cycle, Glycolysis, pentase phosphate shunt
-
all life requires are these 3
- electron flow to drive all life processes
- energy to move molecules
- materials to make cell parts
-
drives ins into/out of cells and is used to create ATP
electron flow
-
materials to make cell parts example is nutrients
-
predominant E source in microbial metabolism is
electricity
-
How is the E source of microbial metabolism electricity
electrons get passes from A to B via oxidation and reduction. the E of the electron flow powers the cell
-
electron flow requires these 2
- source of electrons
- ultimate electron acceptor
-
2 sources of electrons for electron flow needs
-
inorganic molecules are electron donors for this source of electrons
lithotrophs
-
organic molecules are electron donors for this source of electrons
organotrophs
-
inorganic molecules that act as ultimate electron acceptors are these 2
- aerobic (oxygen)
- anaerobic (nitrate)
-
organic molecules that act as ultimate electron acceptors is
fermentation (pyruvate to lactic acid, ethanol)
-
ultimate electron acceptors are these 2 kinds of molecules
-
2 sources of E for microbial metabolism
-
excited molecules are electron donors in this source of energy obtaining microbes
phototrophs
-
chemicals are electron donors in this source of E obtaining microbes
chemotrophs
-
carbon source for biomass
major material
-
CO2 assemble into organic molecules
autotroph
-
acquired organic molecules as carbon source
heterotroph
-
a chemotroph that obtains its electrons and carbon from organic molecules (organotroph)
chemoheterotroph
-
a chemotroph that obtains its electrons from inorganic molecules and its carbon from CO2 (lithotroph)
chemoautotroph
-
a phototroph that obtains electrons from water (oxygenic) and carbon from organic molecules
photoheterotroph
-
a phototroph that obtains electrons from sulfuric acid (anoxygenic) and its carbon from CO2
photoautotroph
-
most organotrophs are also heterotrophs
many microbial organisms can use a combo of metabolic pathways
-
must be supplied from the environment
nutrients
-
4 ions necessary for protein function
Mg, Ca, Fe, K
-
different microbes require different additional nutrients
amino acids, N from air/soil, electron acceptors, energy source
-
contains only the compounds needed for an organism to grow
minimal medium
-
N2 makes up 79% of earth's atmosphere but is unavailable for use by most organisms
-
oxidize ammonia to nitrate
nitrifiers
-
convert nitrate to N2
denitrifiers
-
N2>nitrogen fixers>NH4>nitrifiers>NO3>denitrifiers>N2
-
nitrogen fixing bacteria may b free living in soil or water, or they form symbiotic association with plants
-
3 functions of symport and antiport active transports
- gradient of one molecule transports another
- transports material against its concentration gradient
- can us Na gradient to import amino acid
-
electron transport creates PMF which transports other molecules
-
ATP binding cassette (ABC transporters) are the superfamily of transporters
-
ABC transport functions
use ATP E to pass material in/out of cell against gradient
-
3 functions of siderophores (nutrient uptake)
- molecules secreted t scavenge iron
- imported via ABC transporters
- can bind to other metals
-
active transport of nutrient uptake
phosphotransferase system PTS
-
3 characteristics to PTS
- group translocation system
- uses E to pass material into cell
- modifies material as it enters the cell
-
PTS explained: glucose enters cell and s phosphorylated. As a result, gradient of G pushes more G inside while the phosphorylated ones cannot leave
-
has all materials necessary for growth
culture media
-
what are the 4 components of a culture media
- electron source
- energy source
- carbon source
- nitrogen source
-
the culturing media varies for different bacterial species.
-
A culturing media needs an energy source if its
not phototrophic
-
A culturing media needs a carbon source if its
not autotrophic
-
A culturing media needs a nitrogen source if its
not N2 fixer
-
6 different types of culture media
- liquid vs solid
- minimal vs complex
- enriched with blood
- selective
- differential
- MacConkey medium
-
2 functions of MacConkey medium
- selects against gram+
- differentiates lac metabolism
-
are nutrient rich and poorly defined
complex media
-
are precisely defined
synthetic media
-
are complex media to which specific blood components are added
enriched media
-
favor the growth of one organism over another
selective media
-
exploit differences between two species that grow equally well
differential media
-
all cells in a colony derive from a single cell
-
the single cell makes a colony that contains cells that are genetically identical (clone of that original cell)
-
2 dilution streaking characters
- streak cells on plate
- agar inhibits spread of microbes on plate
-
dilution in liquid culture does what when it comes to obtaining pure cultures
reduces number of cells in each tube
-
what does dilution in liquid culture determine
colony forming units
-
in dilution in liquid culture you spread liquid on plate to see single colonies
-
disadvantage of petroff hausser chamber when looking at cells
can't tell if cells are alive or dead (stain to distinguish living cells)
-
counts cells directly using microscope and gives accurate numbers
petroff hausser chamber
-
in the petroff hausser chamber directly in the middle, there are 25 groups of 16 small squares
-
measures optical density and gives rapid measurement
spectrophotometer (uses light scattering)
-
disadvantage of spectrophotometer
cant tell if cells are dead or alive
-
in spectrophotometer the solution must be 10^7-10^10 cells/ml
-
3 viable counts characteristics
- counts only cells able to reproduce
- requires time to form colonies
- viable counts usually lower than direct counts
-
cells are synthesizing materials and are not dividing
lag phase
-
exponential growth, doubling of growth
log phase
-
log phase increases linearly
-
cells are no longer growing
stationary phase
-
4 phases of the growth cycle in a liquid batch culture
- lag phase
- log phase
- stationary phase
- death phase
-
g=t/n generation time
k=n/t mean growth rate constant
-
cells secrete material to hold to a surface
biofilms
-
4 characteristics of biofilms
- cells act together
- cells signal each other
- protects against dispersion
- prevent antibiotics from infiltrating
-
when cells act together in biofilms they could be from multiple or single species
-
when cells signal to each other in biofilms
quorum sensing
-
when bacteria are faced with environmental stress, they undergo molecular reprogramming such as changes in cell structure
-
these two spores can produce dormant spores that are heat resistant
-
when starvation initiates, an 8 hour genetic program occurs that involves
an asymmetrical cell division process that produces a forespore and ultimately an endospore
-
sporulation can be divided into discrete stages based primarily on morphological appearance
-
2 ways cells respond to a changing environment
-
in heterocysts, the different cells produce different nutrients
-
What heterocyst cells produce energy
vegetative cells
-
what heterocyst cells fix nitrogen
heterocysts
-
in response to the environment, these kind of cells form inside fruiting bodies
myxospores
-
the fruiting body formed by myxospores is a multicellular structure
-
actinomycetes respond to the changing environments by
forming spores
-
when do actinomycetes form spores
when food runs out
-
3 functions of the spores created by actinomycetes
- produce aerial hyphae
- protect
- distributes cells
-
micronutrients are required by cells because they are components of cofactors, what are cofactors
small molecules that fit into specific enzymes and aid as catalysts
-
how were microbes found
DNA amplifying procedure called PCR can be used to screen for the presence of genes in soil and water samples and is compared to the DNA of similar genes from different organisms
-
the critical process of the carbon cycle involves these 2 metabolic groups of organisms
-
is a cell molecule critical to energy metabolism
NAD
-
build biomass by fixing CO2 into complex organic molecules
autotrophs
-
autotrophs gain energy through 2 metabolic routes
- photoautotrophy
- chemoautotrophy
-
produces E from oxidizing inorganic molecules such as iron. E is used to fix CO2 into biomass
-
a type of photosynthetic microorganism produced most of the oxygen we breathe and form the base of the food chain
cyanobacteria
-
nitrifying bacteria gain E by oxidizing ammonia to produce nitrate
-
E stored by an electrical potential across the membrane is known as
membrane potential
-
chemical energy in a cell
ATP
-
2 types of E useful to the cell
-
how is membrane potential generated?
when chem E is used to pump protons outside of the cell so the proton conc is greater outside, an electrical gradient across the cell membrane is generated
-
capable of utilizing photosynthesis or heterotrophic respiration depending on environmental conditions
mixotrophic
-
3 ways selective permeability is achieved
- use of substrate specific carrier proteins in mem
- aid of nutrient binding proteins that patrol the periplasmic space
- action of mem spanning pro channels or pores
-
nutrients that aren't permeable to the mem, microbes secrete digestive enzymes that breakdown the molecule into smaller compounds
-
facilitated transport cannot move a molecule against its gradient
-
most important facilitated diffusion transporters are those of the aquaporin family that transport water and glucose
-
most common chemical gradient used are those of ions, specifically +
-
electron neutral coupled transport in which there is no transfer of charge antiporter
Na/H antiporter
-
a healthy cell maintains proper charge balance using the electron transport chain to move protons in and out of cell, nonbalanced mem, it cannot carry out simple transport that it needs to sustain life
-
major function of proton transport is to create the PMF that powers ATP synthesis
-
ABC transporters are used as multidrug efflux pumps that allow microbes to survive exposures to hazardous chemicals
-
microbes have the fastest and slowest growth rates of known organisms
-
the environmental habitat that a species inhabits is based on one main criterion
the tolerance of that organisms proteins and other macromolecular structures to the physical conditions within that niche
-
4 environmental limits of microbial growth
- temp
- ph
- osmolarity
- oxy
- pressure
-
growth rates increase with temp but if too high proteins denature
-
type of microbe that can withstand 0-20 C
psychrophiles
-
type of microbe that can withstand 12-45 C
mesophiles
-
type of microbe that can withstand 40-80 C
thermophiles
-
type of microbe that can withstand 65-113 C
extreme thermophiles
-
what is a microbes response to high temp
heat shock response
-
2 occurrences to heat shock response
- emergency proteins produced
- keep proteins from denaturing
-
2 kinds of emergency proteins produced in heat shock response
-
what 3 cause heat shock response
- heat
- high salt conc
- arid conditions
-
are adapted to high pressures
barophiles
-
they can grow at high but not too high of pressure
barotolerant organisms
-
they die at high pressure
barosensitive organisms
-
measure of how much water is available for use
water activity
-
the measure of the # of solute moleules in a solution
osmolarity
-
this is inversely related to water activity
osmolarity
-
these help protect the cell from osmotic stress
aquaporins
-
solutes raise osmolarity
high osmolarity reduces available water
-
these organisms require high conc of NaCl and live in salt seas
halophiles
-
ph levels alter the conc of protons
-
bacteria regulate internal ph
-
these organisms grow at a pH of 5-8 and have bacteria in their gut
neutrophils
-
these organisms grow at pH of 0-5
acidophiles
-
grow at a pH of 9-11
alkalophiles
-
can only grow in O2
strict microbes
-
grow only at lower O2 levels
microaerophiles
-
die in the presence of O2
strict anaerobes
-
grow in oxygen while retaining a fermentation based metabolism
aerotolerant anaerobes
-
anaerobes pass electrons to different ultimate electron acceptors
-
have inorganic electron acceptors
anaerobic respiration
-
have substrate level phosphorylation as electron acceptors
fermentation
-
two enzymes exist to neutralize the toxic forms of oxy formed as byproducts of reduction of oxygen
- catalase
- superoxide dismutase
-
4 types of toxic oxygen
- superoxide O2-
- hydrogen peroxide
- hydroxyl radical OH.
- water
-
4 ways to control measures of microbes
- sterilization
- disinfection
- antisepsis
- sanitation
-
killing of all living organism
sterilization
-
killing or removal of pathogens from inanimate objects
disinfection
-
killing/removal of pathogens from the surface of living tissues
antisepsis
-
reducing the microbial pop to safe levels
sanitation
-
D-value
decimal reduction time (time to kill 90%)
-
2D-values
time to kill 99% of cells
-
antimicrobial agents decrease D-value
-
moist heat is more effective than dry heat
-
boiling water kills most cells
-
killing spores and thermophiles usually requires a combo of high pressure and temp (autoclave)
-
steam autoclave
high heat and pressure for 20 min
-
diff time and temp combos can be used for this
pasteurization
-
in pasteurization low temp=long time high temp=short time
-
this slows growth and does not kill all bacteria
cold temp (refrigeration)
-
viruses are not removed in this method of physical agents
filtration
-
2 functions of disinfectants
- kills disease causing organisms
- destroys eukaryotic cells
-
this chemical agent is benchmark comparison to phenol and examples of it are chlorine and iodine
-
this chemical agent is less toxic for living tissues and has conc
antiseptics
-
3 chemicals that damage proteins, lipids, and DNA
-
commercial disinfectants and antiseptics are used to reduce or eliminate microbial content from objects
-
this chemical agent selectively kills microbes and may not work on all species
antibiotics
-
3 characteristics of antibiotics
- kills selective microbes
- has minimal effect on eukaryotic cells
- interferes with bacterial specific enzymes
-
slow growing bacteria take longer to die
-
this blocks cell wall synthesis
penicillin
-
good bacteria that displace disease organisms from tissues
probiotics
-
bacteria can undergo cell diff in response to environmental stress
-
a medium containing bile salts and crystal violet selects for growth against
gram positive
-
if 1 ml of a 10^-4 dilution of a cell culture yields 98 colonies on an agar plate, how many colony forming units/ml are there in the original culture?
9.8x10^5
-
endospores are resistant to many stresses that would kill vegetative cells
-
endospores are durable and can remain viable for years
-
if an enzyme of the PTS system was nonfunctional, the import of all substrates dependent on the PTS system would eventually stop
-
these help move iron into bacteria
siderophores
-
if a bacterium can divide once an hour, after 5 hours, 1 bacterium will yield
32 bacteria
-
how is a continuous culture different from a batch culture
new media is added and old media is removed
-
biofilms may cause health problems for humans
-
complex media are easier to prepare than synthetic media and bacteria grow faster on complex
-
cyanobacteria is an example of
photoautotrophs
-
cells are more negative inside, so when couple transport moves nutrients into the cell against their conc gradient is most likely to occur along
with the electrical gradient of + ions into the cell
-
these kind of transporters bind ATP on the intracellular side of the cell mem
ABC transporters
-
a permease that moves an uncharged sugar into the cell along with a protein, this is classified as
electrogenic symporter
-
these organisms need to ingest reduced carbon
heterotrophs
-
autotrophs are self feeding
lithotrophs generate ATP from reduced inorganic compounds
phototrophs generate ATP through light E
-
of cells in batch culture, they will not remain at a constant mass
-
a bacterial pathogen that can cause an infection in the blood is most likely a
neutrophile
-
barophiles are also psychrophilic because that are usually found in cold ocean depths
-
organisms with high rate of growth at low nutrient conc
oligotrophs
-
organisms that must use O2 as a final electron acceptor in ETC are
strict aerobes
-
piezophiles are also known as
barophiles
-
aerobes may tolerate the presence of O2 because they have the enzyme
superoxide dismutase
-
is the addition of nutrients to an ecosystem
eutrophication
-
eutrophication may lead to decreased microbial diversity
-
many alkalphiles have a sodium motive force because it will be hard to maintain a PMF in an alkaline environment
-
phage therapy refers to
the idea that phages could be used to treat bacterial diseases
-
bacteria cannot regulate their temp
-
chemotrophs whether they be auto or hetero oxidize and reduce compounds to get E
-
in chemotrophy, the amnt of E gained from Ox a compound if related to the compounds red state. The more red the compound is, the more e- it has to give up and the high the PE yield.
-
chemoautotrophy is the same as
lithotrophy
-
fungi require complex organic molecules for their growth; some of their lifestyles involve these 3
- predation
- parasitism
- scavenging the dead
-
obligate intracellular bacteria lose metabolic pathways provided by their host and develop requirements for growth factors supplied by their host
-
autotrophs male complex organic molecules that are consumed by
heterotrophs
-
eukaryotes carry out only a limited range of heterotrophic and photo rxns
-
how do symports and antiports function
by alternatively opening one end or the other of the channel that spans the membrane
-
the inside of the cell has to be kept negative while the outside is to remain positive
-
ABC transporter consists of 2 hydrophobic proteins, that form a membrane channel and two peripheral cytoplasmic proteins that contain a highly conserved amino acid motif involved with binding ATP
-
amino acid sequence found in a family of proteins
cassette
-
the uptake systems of ABC transporters possess an additional extracytoplasmic protein called
substrate binding protein
-
SBP have a high affinity for their matched solutes, their use increases the efficiency of transport when conc of solutes are low
-
SBP binds to the face of the protein to open the channel after a structural change is made to open
-
once the signal is received from the opened channel with the SBP, the nucleotide binding proteins start to hydrolize ATP and signal the channel to open the cytoplasmic side to allow the entrance of solutes
-
Fe scavenger molecules secreted from siderophores occurs when intracellular iron conc is low
-
PTS is a well characterized group trabslocation system present in many bacteria
-
eukaryotes undergo exocytosis to and endocytosis to bring in and take things across the cell membrane, they also have pumps as well
-
lysosomes bind with phagosomes to creat phaglysosomes which help the digestive enzymes breakdown the endocytosed material
-
this medium is useful when
studying the growth characteristics of a single strain of species
-
this kind of media is useful when trying to separate mixtures of diff organisms as they are found in the natural environment
solid media
-
spread plate starts from a liquid batch of bacteria, a series of tenfold dilutions is made and a small amount od each dilution is placed directly on the surface of the agar plates
-
an organism that successfully replicates to form a colony
viable organism
-
CFU are chains of cells that have not split and look like a group of cells
-
straightforward approach to monitoring pop growth is the measure the dry weight of a culture from cells collected by centrifuge, washed and dried in an oven then weighed.
-
optical density of light scattered by bacteria is a very useful tool for estimating pop size
however, the cell # is based on optical density, the cells volume can vary. It wont get an accurate measure of the number of cells
-
if a cell produces 2 cells per generation then it will be 2^n
n= the number of generations
-
bacteria divide at a constant interval called
gen time
-
generation time varies with respect to the species, type of medium, temp, and ph
-
no fresh media is added during the incubation of this kind of culture
batch culture
-
simplest way to model the effects of changing conditions is to culture the bacteria in a liquid medium within a closed system called
batch culture
-
batch media illustrate the remarkable ability of a bacteria to adapt to their environment
-
a chemostat in which a photoelectric cell constantly monitors the optical densityof the culture
turbidostat
-
biofilms can be cued by different environmental signals such as ph, Fe conc, temp, etc.
-
starvation triggers a developmental cycle in which 100,000 of more individuals aggregate rising into a mound called a fruiting body
-
are bacteria that form mycelia and sporangi analogous to a filamentous structures of eukaryotic fungi
-
this allows us to study the biology of organisms that we cannot culture
bioinformatics analysis
-
this reveals whether or organism under study may possess specific metabolic pathways and regulatory responses
genomic comparison
-
every organism has an optimal that in which they perform their best at, while they also have a minimal and a maximum which limits them to what they can handle
-
-
2 reason as to why psychrophiles like cold
- their proteins are less flexible and require less E to function
- mem are more fluid at low temp
-
psychrophile enzymes are of commercial interest because of their ability to carry out reactions at low temps, this could help with food processing
-
thermophiles proteins do not unfold as easily so they can hold their shape at higher temps
-
like all microbes thermophiles have chaperone proteins that help refold other proteins as they undergo thermal denaturation. Their genomes are packed with DNA binding proteins hat stabilize DNA and make it less likely to denature
-
the membranes of the thermophiles glue together parts of the 2 hydrocarbon layers making them more stables
-
chaperones function in heat shock response
maintain protein shape and enzymes that change membrane lipid composition
-
increased hydrostatic pressure and cold temps similarly reduce membrane fluidity
-
most bacteria require how much water activity in order for them to grow
greater than .91
-
2 other mechanisms microbes have to help minimize osmotic stress across membranes
- protect their internal water by synthesizing or importing compatible solutes that increase intracellular osmolarity
- have pressure sensitive channels that can be use to leak solutes out of the cell
-
are small molecules hat do no disrupt normal cell metabolism even when present at high intracellular concentrations
compatible solutes (these are used in microbes for minimizing osmotic stress)
-
function of pressure sensitive channels in microbes as a minimizer to osmotic stress
the channels are activated by rising internal pressure in cells immersed in a hypotonic medium, when activated the channels allow solutes to escape which lowers internal osmolarity
-
% and M of NaCl do halophiles need in order to grow
% and M of NaCl do most bacteria need to grow
-
how can halophiles live in high salt conc environments?
they use special pumps to secrete the Na+ and replace it with other cations such as potassium
-
high conc of hydronium or hydroxyl ions in a solution will limit the growth of microbes
-
Altering the PH can alter changes of various amino or carboxyl groups within a protein which can change the proteins structure and activity
-
the Ph and the osmolarity of a microbe is not dictated by its outside environment
-
the cell can become acidic when weak uncharged permeable acids can cross the cell and then dissociate which releases a proton that acidifies the internal pH
-
these organisms can oxidize reduced metals and generate strong acids such as sulfuric acid. They are also known as chemoautotrophs
acidophiles
-
these organisms are commonly found in saline soda lakes which have high salt conc and pH values
alkaliphiles
-
most alkaliphiles use a Na motive force in addition to PMF because external protons are in such short supply at the alkaline pH
-
when cells are placed in pH conditions below their optimum, protons can enter the cell and lower the internal pH to lethal levels.
-
Microbes can prevent the unwanted influx of protons by exchanging extracellular potassium for intracellular protons when internal pH gets too low
-
Under extreme alkaline conditions, the cells can use the Na/H antiporters to recruit protons into the cell in exchange for expelling Na
-
bacterial physiology undergoes a major molecular reprogramming in response to hydrogen ion stress. some of the physiological responses are these 2
- modifications in mem lipid composition
- enhanced pH homeostasis
-
acid and alkaline stress responses occur when
- placing given species under pH conditions that slow its growth.
- the cell increases the level of proteins designed to mediate pH homeostasis and protect cell constitute
-
the use of O2 as the terminal electron acceptor is called
aerobic respiration
-
electrons are pulled from various E sources. They do this by extracting the E in stages and using it to move protons out of the cell. This unequal distribution of H+ across the mem produces a transmembrane electrochemical gradient called PMF
-
this enzyme removes oxide in anaerobes
superoxide dismutase
-
these 2 enzymes remove hydrogen peroxide in anaerobes
-
aerobes have resourceful enzyme systems that detect and repair macromolecules damaged by oxidation
-
facultative anaerobes
aerotolerant
-
these can only use fermentation as E but contain superoxide dismutase and catalase to protect them from reactive oxygen species
aerotolerant
-
anaerobic respiration
fermentation
-
fermentation depends on these two factors
- the availability of O2
- the amount of carbohydrates present
-
3 techniques for culturing anaerobes
- special reducing agents
- agar plates
- anaerobic glove box
-
this kind of technique, enzyme systems can eliminate dissolved oxy so that it can be added to ordinary liquid media
special reducing agents
-
this technique has the organisms streaked and placed into a sealed jar with a foil packet that releases H2 and CO2 gases
agar plates
-
this technique has the atmosphere removed by a vacuum and replaced with a mix of N2 and CO2 gases
anaerobic glove box
-
in result of a starvation response, the metabolic slowdown generates increased conc of critically important small signal molecules such as _____ and _____ which transforms gene expression
-
when the environment continues to get worse, the organism has stress survival genes that become active, these genes protect against stressors such as reactive oxy rad or temp and pH extremes
-
what happens when eutrophication occurs amongst microbes
lead to bloom of microbes, an unrestricted growth consuming other nutrients to a degree that threatens the existence of competing species
-
what causes eutrophication
human activities
-
antimicrobials can either inhibit growth or kill the cells completely
-
the ability of an antimicrobial agent to kill microbes influence the D-value
-
it takes all cell in a population a while to die because not all proteins and genes in a X are damaged by an agent at the same time
-
assume all cells in a pop are identical
-
vegetative cells
activity growing orgainisms
-
boiling water at 100 C can kill most vegetative cells
-
the bombardment of foods with high E electromagnetic radiation
irradiation
-
3 sources of irradiation
- gamma rays
- electron beams
- xrays
-
the amount of E transferred to food, microbes, or other substance being irradiated
gray (Gy)
-
parasites that have a large amount of DNA are killed rapidly by
extreme low doses of radiation, D-values less than 0.1
-
it takes more radiation to kill bacteria because they have less DNA/cell unit
.3-.7 kGy
-
viral pathogens have the smallest amount of nucleic acid making them resistant to irradiation doses
-
irradiation is effective in eliminating parasites and bacteria but not viruses or prions
-
those that don't contain nucleic acid are only inactivated by irradiation at extremely high doses
-
Deinococcus radiodurans is known as conan the bacterium because
this microbe has the greatest ability to survive radiation of any known organism
-
a chemical on a dirty surface will bind to the inert organic matter and lower the agents effectiveness against microbes
-
4 factors that influence the efficiency of a given chemical agent
- presence of an organic matter
- the kinds of organisms present
- corrosiveness
- stability, odor, and surface tension
-
the chemical agent should be effective against a broad range of pathogens
-
the disinfectant should not corrode the surface ex skin
-
the chemical should be stable upon storage, possess a neutral or pleasant odor or have low surface tension so it can penetrate cracks and crevices
-
3 reasons why phenolics are useful disinfectants
- denature proteins
- effective in presence of organic material
- remain active on surfaces long after application
-
detergents can also be antimicrobial agents, the hydrophob and phil ends of detergent molecules will emulsify fat into water
-
+ are useful as disinfectants because they contain + charges that can gain access to the negatively charged bacterial cell and disrupt membrane
-
very effective sterilization it destroys cell proteins and penetrates packing material
ethylene oxide gas EtO
-
chemical disinfectants are compared to one another based on the phenol coefficient
-
are compounds produced by one living microorganism that kill other microorganisms
antibiotics
-
the measure of how much more heat is needed to reduce D-value to 1/10 its original value
z-value
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