UV Radiation, Urine Streak, & Urea Hydrolysis Flashcards
The Electromagnetic Spectrum
the energy radiating from the sun occurs in a wide range of wavelengths
Longer wavelengths…
have LESS energy
Shorter wavelengths…
have MORE energy
note: radio waves are harmless to humans, but gamma rays, x-rays, and UV rays can cause damage to bacteria
UV Light
Non-ionizing radiation classified into UVA, UVB, & UVC
UVC (100-280 nm)
most damaging to bacteria
causes Thymine Dimers in our DNA
Thymine dimers result in errors in replication and transcription of DNA
Bacterial Repair Mechanisms
Photoreactivation & Excision Repair
Photoreactivation (light repair)
the enzyme DNA photolyase which is activated by visible light - reverses the reaction which formed the dimer
Excision Repair (dark repair)
this involves several enzymes which removes a 13 nucleotide fragment on one side - which leaves the other side to act as a template for a new strand (made by DNA Polymerase I)
Urine Streak
A semiquantitative CFU counting method utilizing a volumetric loop (either .001 ml or .01 ml)
A specialized streak method is used to obtain countable colonies on a blood agar plate
OCD = original cell density is determined and reported in CFU/ml
Urea Agar
differential media that identifies organisms that can metabolize urea
Urea is a…
product of decarboxylation of certain amino acids
Urease is a…
enzyme that can hydrolyze urea to ammonia and carbon dioxide
Rapid urease-positive organisms
Proteus, Morganella, & Providencia
note: other enteric can metabolize urea, but not rapidly
Ammonia…
a weak base that acts as a proton acceptor
Phenol Red…
the pH indicator which is pink in basic conditions
