Microbiology Lab: Effects of UV Radiation
What is the optimal wave length to kill microbes?
265nm
What are the ranges of UV radiation wave length?
4nm to 400nm
Why is B. licheniformis less susceptible to UV light?
Because it has a protective spore coat.
What is confluent growth?
Called a "lawn" which is a uniform and uninterrupted layer of bacterial growth, in which individual colonies cannot be observed.
What is the process of this lab?
Cover 1/2 of inoculated plate with index card, expose to UV light for given time period, incubate 24-48 hours, examine.
What does UV light do to bacteria?
It mutates the cells, stopping their growth.
Bactericidal
Kills bacteria
Why is one-half of each plate covered with a card?
To provide a control group.
Why do you remove the cover prior to exposing the dish to UV light?
UV light does not penetrate well, and can not penetrate the plastic.
Preparation Steps
1) Label bottom of plate 2) Use aseptic technique, dip sterile swab into culture 3) Swab entire surface of agar plate. Swab again in right angles (to evenly inoculate the entire plate) 4) Place under UV light with half covered with card 5) Incubate in inverted position
