Question

1. [5 points] The time required for a tenfold reduction of the viability of a microbial population at a given temperature is called the ________ time.
   1. thermal death
   2. mean sterilization
   3. decimal reduction
   4. temperature-dependent logarithmic death

2. [5 points] UV radiation is antimicrobial, because
   1. radiation generates significant amounts of heat within the given cell.
   2. energy present causes modifications or breaks in the DNA molecules.
   3. radiation generates magnetic poles that denature the cellular components.
   4. radiation dissolves bacterial cell walls.

3. [5 points] When a compound is degraded by an enzymatic reaction without yielding any benefit to the microorganism, it is said to be
   1. activation
   2. cometabolism
   3. mineralization
   4. parasitism

Answer 1

1. Answer is c) decimal reduction time

Thermal death time is the time taken to kill a specific bacterium at specific temperature. Mean sterilization means particular time is taken for sterilization. Decimal reduction time meaning is time required to log reduction or kill 90% microorganisms at a particular temperature. Temperature dependent logarithmic death means a logarithmic process where at a specific time interval at a specific time same percentage of bacterial colonies are killed.

2. Answer is b) energy present causes modifications or break in the DNA molecules.

UV radiation use short wavelength radiation which causes destroying of nucleic acid and breakage of DNA into fragments . So the cell can not perform normal function.

3. Answer is b) cometabolism

Cometabolism means degradation of substance into two substances where second substance is degraded in presence of first substances. For this degradation energy is required. This energy is produced by organism to catalyze this degradation process without benefiting microorganism.

Mineralization means a process where inorganic substances incorporated into organic matter. Parasitism is a symbiotic association between two organism where one get harmed and another one become benefited. Activation means making a chemical substance.