week 11: controlling microbial growth Flashcards
two categories of controlling microbial growth
physical, chemical
examples of physical methods
oven, autoclave, boiling, flash pasturization, filtration, uv light
examples of chemical methods
iodine, alcohol, soap, bleach
heat generally kills microbes by
denaturing proteins
sterilization
complete elimination of microbes
dry heat sterilization
requires high temp and longer treatment times
moist heat sterilization tools
reduces temp required
pasteurization is used to
preserve liquids that cannot be boiled
batch pasteurization
65 degrees C for 30 mins
flash pastuerization
72 degrees C for 15 seconds
flash pasteurization kills
mesophiles, most likely to be pathogenic
ultra pasteurization
134 degrees C for 1-2 seconds
how does cold prevent microbial growth
reducing the availability of food
what size filter is small enough to prevent bacteria
0.45um
radiation causes
mutations in the genetic material of a microbe
disinfectants are used to
reduce contamination on non living material
antiseptics are used to reduce contamination on
living tissue
chemotherapeutics are used to reduce
contamination within living tissue
phenolics
kill microbes by denatiruing proteins - listerine and lysol
chlorine
kills microbes by forming an acid when mixed with water
alcohol
kills microbes by denaturing protiens and disrupting cell membranes
detergents
killls microbes by creating leaky cells
heavy metals
kills microbes by interfering with protein structure
bacteria require ______ in order to convert it to folic acid which is essential for replication
para aminobenzoic acid
the enzyme responsible for converting PABA to folic enzyme cannot distinguish between
PABA and sulfanilamide
when sulfanilamide binds to the enzyme instead it
prevents folic acid production, halting replication
why are human cells not affected by sulfa drugs
humans dont have the enzyme that converts PABA to folic acid
spectal activity range, broadest to narrowest
tetracyclin, sulfa drugs, streptomycin, erythromycin, penicillins, isoniazid
drugs that inhibit gram + and - cell walls
penicillins, cephalosporins, vancomycin
drugs that inhibit acid fast cell walls
isoniazid
how do penicillins inhibit cell wall synthesis
penicillins interfere with the synthesis of the pentaglycine bridges that connect peptidoglycan layers in bacterial cell walls. This compromises the integrity of the cell wall causing it to take in water from the environment until it bursts
how does vancomycin inhibit cell wall synthesis
used against gram positive bacters bc cannot penetrate outer membrane of gram negative
how does isoniazid inhibit cell wall synthesis
inhibits mycolic acid synthesis
erythromycin binds to
bacterial ribosome preventing it from moving along the mRNA template; preventing translation
tetracyclines block
binding between tRNA and the ribosome, preventing translation
chloramphenicol blocks the formation of
peptide bonds between amino acids, preventing translation and protein synthesis
streptomycin blocks effective translation by
altering the structure of the bacterial ribosome so that codons are misread and translation is innefective
rifampin binds to
rna polymerase, blocking bacterial transcription
ciprofloxacin inhibits bacterial replication by binding to
DNA polymerase and preventing dna from unwinding
cell wall production in inhibited by
vancomycin, cephalosporins, isoniazide and penicillin
ribosome is inhibited by
tetracyclin, erythromycin, chloramphenicol, streptomycin, gentamycin
enzyme is competitively inhibited by
sulfa drugs
dna replication is inhibited by
ciproflaxin
rna polymerase is inhibited by
rifampin
why is selective toxicity difficult to achieve against eukaryotic microbes
the structure of the cells are so similar to our own
polyenes
binds more readily to ergosterol compared to cholesterol, disrupting the fungal membrane
azoles
interfere with ergosterol synthesis
protozoa
prevent hemoglobin digestion by the parasite while residing in red blood cells
reverse transcriptase inhibitors
mimic the structure of a nucleotide, incorporate it into DNA molecules during reverse transcriptase; ultimately preventing DNA replication
protease inhibitors
prevents proteases from cleaving large proteins into smaller fragments important for viral synthesis
why is acyclovir used against herpesvirus
resembles sugar base subunit, acting as a false nucleoside, viral replication is selectively hindered while host DNA replication remains
