EFFECT OF ULTRAVIOLET RADIATION ON MICROORGANISMS Flashcards
What are the effects that the ultraviolet produces?
Germicidal effects
What causes peroxides to form in the exposed medium, that turns as oxidizing agents?
Ultraviolet light
T/F:
Exposure of nucleic acids to ultraviolet radiation can cause mutations
TRUE
Why does the exposure of nucleic acids to UV radiation cause mutations?
Because of abnormal linkages forming between nitrogenous bases
What forms a thymine dimer after exposure to ultraviolet radiation
thymine combines with other thymine groupings
T/F:
The greater the amount of UV radiation released, the greater the number of mutations that will occur.
FALSE, the greater the amount of UV radiation absorbed
What is the purpose of the effect of ultraviolet radiation on microorganisms experiment?
To determine the minimum amount of exposure required to affect a 100% kill
MATCHING:
- Bacillus Megatarium
- Staphylococcus aureus
a. ) non spore former
b. ) spore former
Bacillus megatarium - spore former
Staphylococcus aureus - non spore former
Which species had more growth with the 0 sec (control) - 0.5 min exposure time?
Which had no growth in 1 - 2 min? both
Both the Staphylococcus aureus and Bacillus megatarium
Describe the damaging effects of UV radiation on living cells. At which wavelength is UV radiation most germicidal?
- UV causes damage to DNA by causing formation of pyrimidine dimers
- 260nm, this is the max. wavelength the DNA absorbs
Why does exposure to UV radiation cause death in vegetative cells but not endospores?
- Vegetative cells do not have repair and protection mechanisms
- Endospores are more protected by proteins and repairs DNA
Which B. megatarium culture, logarithmic or stationary phase, would show the best survival following exposure to UV radiation? WHY?
the stationary phase. Many bacterium would have formed endospores
What is a logarithmic phase?
- one of the phases observed in a bacterial growth curve
