Exercises 8-3 – Ultraviolet Radiation Exercise 6-3 – Urine Streak Exercise 5-15 – Urea Hydrolysis

• Colony-Forming Unit (CFU)

a unit of measurement used in microbiology to estimate the number of viable microbial cells in a sample

• OCD – Original Cell Density

a calculation used to determine the density of a sample:

Urea

a naturally occurring molecule that is produced by protein metabolism and found abundantly in mammalian urine

Urease

an enzyme that breaks down urea into ammonia and carbon dioxide through a process called hydrolysis

Ammonia

A gas made of nitrogen and hydrogen

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

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

ULTRAVIOLET LIGHT (UV)

aka NON-IONIZING RADIATION -

- UV waves are classified into 3 types

UVA, UVB, UVC

UVC - (100-280 nm) -

most damaging to bacteria

 causes Thymine Dimers in our DNA (adjacent Thymines covalently bond together)

 Thymine dimers result in errors in replication and transcription of DNA

types of BACTERIAL REPAIR MECHANISMS

PHOTOREACTIVATION (Light Repair) - and EXCISION REPAIR (Dark 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)

pyrimidines

cytosine, thymine, and uracil.

Urease-positive organism color

pink color

Urease-negative organism color

orange yellow colr

uninoculated control color

black