Ultraviolet Radiation and Urea Hydrolysis

The electromagnetic spectrum

the energy radiating from the sun occurs in a wide range of wavelengths

Thymine dimers

formed between pyrimidines

LONGER WAVELENGTHS

have LESS energy

SHORTER WAVELENGTHS

have MORE energy

True

Radiowaves are harmless to humans, whereas, gamma rays, X-rays and UV rays can cause damage to bacteria

UV waves are classified into 3 types

UVA, UVB, UVC

DNA PHOTOLYASE

PHOTOREACTIVATION (Light Repair) -
The enzyme is activated by visible light and reverses the reaction which formed the
dimer

light repair

photoreactivation
- DNA photolyase activated by visible light

EXCISION REPAIR

(Dark Repair) -
This involves several enzymes which remove a 13-nucleotide fragment on one side - which leaves the other side to act as a template for a new strand (DNA Polymerase I)

Ultraviolet light

NON- Ionizing Radation

UVC

causes Thymine Dimers in our DNA (adjacent Thymines covalently bond together)
*Thymine dimers result in errors in replication and transcription of DNA

OCD

Original Cell Density

Original Cell Density

is determined and reported in CFU/ml

Urea production

by decarboxylation of certain amino acids

* Primary nitrogenous waste in the urine of many mammals

Urea

can be hydrolyzed to ammonia and carbon dioxide by bacteria having the enzyme called urease

Enteric bacteria

possesses the ability to metabolize urea

Urea Agar

ONLY a differential media that Identifies organisms
that can metabolize urea

pH indicator

used to track rising pH due to accumulation of ammonia

Urea broth

nutrient source other than urea is trace amount of yeast extract

Pink

rapid urea hydrolysis, strong urease production  Urease-positive organism

Orange or Yellow

No urea hydrolysis, urease is absent or not produced in enough quantity to
produce result in 24 hours, organism cannot live in urease broth

* Urease-negative organism

UREASE

an enzyme that can hydrolyze urea to ammonia and
carbon dioxide

rapid urease-positive organisms

*Proteus, Morganella, & Providencia are considered

Ammonia

(a weak base) acts as a proton acceptor

Phenol Red

the pH indicator which is pink in basic conditions

Urease positive organisms

Color entire slant pink within 24 hrs

Thymine molecules

interfere with DNA replication

Bacteria

have mechanisms to repair DNA damage

DNA ligase

closes gap between the last nucleotide of the new segment and the first nucleotide of the old DNA (completed repair)

Urea

a product of decarboxylation of certain amino acids

Urea

Provides nitrogen in a usable form (ammonia) and acts a virulence factor for pathogens such as Helicobacter pylori