Question

Please complete all questions (1-5). For question 5, construct a x-y scatter plot graph with UV exposure time on x-axis and amount of growth (0,1,2,3) on Y axis. use a different color or symbol per organism and DO NOT connect the dots. Thank you!

2-12 The Effect of Ultraviolet Radiation on Microbial Growth OBSERVATIONS AND INTERPRETATIONS 1 Enter your class data in the table below using the following descriptions: 0 - no growth 1 individual colonies 2 - sparse confluent growth 3 heavy confluent growth B. subtilis B. subtilis UV Exposure 124-hour culture) (7-day culture) D.radiophilus (minutes) Side A Sides Side B Side A Sider Side A Side B 13 E.coli 4 03 12 16 3 QUESTIONS The purpose of this exercise is to demonstrate the comparative effect of UV on four bacterial population This could have been accomplished without the cardboard cover. Why was the cover used?

answer questions 1-4 please.

Answer 1

Answer 1. There are two main reasons for using the cover. Firstly UV is dangerous to every cell and the surroundings in which UV related experiments are done should be well covered for safety. Secondly while working with the cardboard covering, it is ensured that complete exposure to UV is provided to the bacterial cells.

Answer 2. UV causes DNA damage, therefore longer exposure time will lead to more DNA damage and more cell death. Therefore when we increase the exposure time cell death increases.

Answer 3. When bacteria are exposed to harsh conditions, lack of nutrients some bacteria have the ability to form endospores. Endospore formation is a characteristic feature of several bacteria, however, gram-positive bacteria are mostly spore-forming bacteria. Bacillus (gram-positive) species have the characteristic ability to form spores therefore they are able to evade UV exposure. Since E.coli are non spore-forming they are killed by UV exposure.

Answer 4. While conducting the experiment it is highly important to expose the bacteria in all plates to UV light such that each plate is well penetrated by UV light. To ensure that the lid does not cause any hindrance to the UV exposure, lids are removed prior to the experiment.

Answer 5. Graph. Red and orange dots overlap each other for B. subtilis(side B) and E.coli(side B).

Amount of growth 0 2 4 14 16 18 6 8 10 12 UV EXPOSURE(min) • B. subtilis(A) B.subtilis(B) E. coli(A) E. coli(B)