Resistance Flashcards
what is recombination
breaking and joining of DNA in new combinations
type of recombination
- homologous (between similar/identical DNA)
- non homologous (“cut and paste” - transposition)
integration of DNA acquired by
transduction, conjugation, transformation
what are transposons
jumping genes
move from:
chromosome -> chromosome
chromosome -> plasmid
how do transposons move around within these sites
non‐homologous recombination: site‐specific recombinases (the transposase enzyme)
difference between structure of simple and complex transposon
in simple: no selectable genes (inverted repeat, transposase, inverted repeat which makes up the IS)
complex: IS, genes for eg. penicillin, IS
how do transduction, conjugation, and transformation transfer resistant regene
transduction - bacteriophage
conjugation - plasmid
transformation - DNA binding proteins
explain the process of transformation
bacterial cell dies and DNA is broken up, 2 strands of the DNA is grabbed by the DNA binding protein, 1 strand is degraded and 2nd is recombined and incorporated into competent cell
what are some competent cells for transformation
streptococci and haemophilus
what microorganisms carry out conjugation and why
gram negative bacteria because it requires production of pilus
what encodes the pilus
F-factor (plasmid)
what does the F factor plasmid contain
tra genes (transfer) and of course genes for pilus production
how are cells defined in conjugation
– F+ (have F‐factor plasmid)
– F‐ (lack F‐factor plasmid)
what is used to transfer plasmid from F+ donor cell to recipient cell
pilus
types of phages in transduction
virulent (lytic) - death of cell by lysis hence releasing new phage
temperate: phage DNA gets integrated with host cell DNA (prophage), cells replicate, then there’s a change where cells them become virulent and begin to lyse and release new phages
what is it called when bacteria are carrying a prophage
lysogeny
what happens when alcohol concentration is greater than 50%
dissolve membrane lipids, disrupt cell surface
tension, affect membrane integrity
alcohol acts as a microbicial agent against what microorganisms
vegetative fungi, fungal spores, enveloped viruses
NOT BACTERIAL SPORES
what is the activity of halogen eg iodine
microbicidal and sporicidal (with longer exposure)
what are applications of halogens
chlorine: water tx
iodine: iodophors eg betadine
halogens as oxidizing agents affect what?
cellular enzymes
example of disinfectant
sodium hypochlorite (bleach)
how does steam heat (autoclave) work
it coagulates protein hence breaking hydrogen bonds
advantage of steam heat
will kill all microorganisms and most endospores within 15 mins
uses of steam heat
culture media, solution, dressings, instruments
what is steam heat not used for
heat sensitive items
what is ethylene oxide gas
chemical sterilizing agent when used in gaseous form
why is ethylene oxide gas considered a strong alkylator
reacts with guanine of DNA and functional groups of proteins
advantages and disadvantages of ethylene oxide gas
advantage - for all organisms and endospores, suitable for temp or moisture sensitive items
disadvantage - Longer treatment time compared to autoclaving: 16‐18 hours
used to disrupt DNA
Ionizing radiation e.g., gamma rays
used for disruption of cell membrane
microwave (non ionizing radiation)
Free radicals interact with the cell membranes, enzymes, or nucleic acids
hydrogen peroxide
plasma
used for oxidation eg cell membranes
ozone gas
