week 11 staph, effects of temperature, osmotic pressure and UV light

organisms used for UV light

S. aureus and B. Cereus (endospore former)

DNA is sensitive to what kind of radiation

non ionizing radiation resulting in pyrimidine dimers

how is pyrimidine dimer repair done

SOS system
enzymatic removal of dimers

killing properties of UV light

time of exposure, presence of material to block radiation (glass and plastic), endospores (more resistant to UV than vegetative cells)

organisms used for temperature effects

S. marcescens

psychrophiles

between -5 celsius and 20 celsius; arctic and antarctic regions

mesophiles

between 25 and 45 celsius; most bacteria fall in this class; pathogens form 35-45

thermophiles

between 45-70 celsius; soil bacteria

hyperthermophiles

above 75 celsius; archaea living near volcanoes

effects of temperature on enzymes

above = denature
below = slow down

effect of temperature on cell membrane transport

low temps = lower transport rates
higher temps = membrane degradation

effects of temperature on ribosomes

cease to function at either temperature extreme

what is the red pigment of S. marcescens called

prodigiosin (enzyme product and seen at certain temperatures)

organisms used for osmotic pressure

S. aureus, E. coli and H. salinarium

Aw

water activity

osmosis

water diffusion from low solute to high solute concentration

hypertonic

water lost to environment

hypotonic

water rushes into cell = lysis

isotonic

solute concentration is same

halophiles

grow best at high concentrations of salt

halotolerant

grow at moderate salt concentrations
ex = staph

methods for isolation and identification of staphylococci

enriching cultures and media: MSA and SM110

percentage of population that is carrier of s. aureus

20-30%

what percent of population is carrier of MRSA

2%

2 plates used for staph isolation

MSA and SM110

MSA

has sodium chloride, mannitol, phenol red indicator (sugar fermented = acid produced = phenol red to yellow)

SM110

sodium chloride and mannitol, no phenol red indicator, favors colony pigmentation