Name the two principal halogens and the two principle gases that we discussed in

Question

Name the two principal halogens and the two principle gases that we discussed in class practical applications in controlling microorganisms. (2 pts) as ha vin 28. Halogen # 1 Halogen #2 Gas #1 Gas #2 29. List the two most common factors responsible for batch cultures (e.g. bacteria growing in a flask) to cease growing exponentially and enter stationary phase. (2 pts) 2. 30. List two disadvantages associated with the use of ethylene oxide as a sterilizing agent. (2 pts) 2. 31. With respect to bacteria, explain why the physiological effect of HCL at pH 4 is not as that of an organic acid (e.g., Benzoic Acid) at pH 4. (2 pts)

Explanation / Answer

28. Halogen #1 :- Iodine ; Halogen #2 :- Chlorine

Gas #1 :- Ethylene oxide  ; Gas #2 :- Ozone

29. 1. Limited space 2. Limited nutrients

30. 1. Ethylene oxide is toxic to humans. 2. It needs several hours of exposure to acheive sterilization.

31. Permeant weak organic acids are known to be more effective against bacteria than inorganic strong acids like HCl. Benzoic acid stress induces a slower transcriptional response and large variations in growth patterns compared with the responses induced by HCl. In cultures acidified with benzoic acid, the pH of the medium gradually increases during growth, while no such increase occurs in bacteria exposed to HCl. Measured by growth inhibition, benzoic acid stress introduces severe stress compared with that caused by HCl.

35. a) energy source that powers group translocation is Phosphoenolpyruvate (PEP).

b) Substrate outside the cell before transport is Glucose. Inside the cell it is modified and released as -6-phosphate.

c) Sugars like glucose etc are brought into the cell by group translocation.

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