Problem 1
The thermal death time for a suspension of Bacillus subtilis endospores is 30 minutes in dry heat and less than 10 minutes in an autoclave. Which type of heat is more effective? Why?
Problem 2
If pasteurization does not achieve sterilization, why is pasteurization used to treat food?
Problem 3
Thermal death point is not considered an accurate measure of the effectiveness of heat sterilization. List three factors that can alter thermal death point.
Problem 4
Define oxidation-reduction, and differentiate the following terms: a. aerobic and anaerobic respiration b. respiration and fermentation c. cyclic and noncyclic photophosphorylation
Problem 6
All of the energy-producing biochemical reactions that occur in cells, such as photophosphorylation and glycolysis, are _______ reactions.
Problem 7
How do salts and sugars preserve foods? Why are these considered physical rather than chemical methods of microbial control? Name one food that is preserved with sugar and one preserved with salt. How do you account for the occasional growth of Penicillium mold in jelly, which is \(50 \%\) sucrose?
Problem 8
The use-dilution values for two disinfectants tested under the same conditions are as follows: Disinfectant A-1:2; Disinfectant \(\mathrm{B}-1: 10,000\). If both disinfectants are designed for the same purpose, which would you select?
Problem 9
Why must NADH be reoxidized? How does this happen in an organism that uses respiration? Fermentation?
Problem 9
A large hospital washes burn patients in a stainless steel tub. After each patient, the tub is cleaned with a quat. It was noticed that 14 of 20 bum patients acquired Pseudomonas infections after being bathed. Provide an explanation for this high rate of infection.
Problem 10
What nutritional type is a colorless microbe that uses the Calvin-Benson cycle, uses \(\mathrm{H}_{2}\) as the electron donor to its ETC, and uses elemental \(\mathrm{S}\) as the final electron acceptor in the ETC?
