Difference between gram positive and gram-negative cultures

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Assignment:

You are to perform a lab looking at the effects of UV light. The lethal effect of ultraviolet radiation will be examined and compared on microbial growth of: 24hr culture of E. coli, 24hr culture of S. epidermidis, 24hr culture of B. subtilis and 7d culture of B. subtilis. The procedure starts with 4 agar plates split in half as 'A' and B' with a marker. Each plate is then inoculated with one of the bacterial cultures. A paper towel is then placed on the bench next to the UV lamp and soaked with 70% ethanol. The lids are removed and the 4 plates are placed upside down on the alcohol soaked paper towel with side 'A' exposed to the UV light and side 'B' is covered by foil-covered cardboard rectangles. At the end of desired exposure time the lids are placed back on and the plates are incubated.

1. For each culture, what is the effect of increased UV exposure time on growth on both the covered "B" and exposed "A" sides of plates?

2. Is there a difference between gram positive and gram-negative cultures?

3. Is there a difference between 24h and 7d B. subtilis cultures? If so, what can account for this difference?

4. What is the reason for using the foil rectangle?

5. Why do we rest the plate lids on alcohol-soaked paper towels?

Reference no: EM133469449

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