Question

In fluctuation test experiments, bacterial mutation to phage resistance is examined by growing separate bacterial cultures for several generations, then plating the bacteria together with the phage. The number of resistant colonies per culture fluctuates (varies) between cultures: most yield a few resistant colonies, but some cultures had many. These results imply that mutations to phage resistance....

A. - are induced by phage infection, but at different rates in different cultures.

B. - happen independently of phage infection, but at different times in different cultures.

C. - are induced by phage infection, but at different times in different cultures.

D. - happen independently of phage infection in most cultures, but are induced by phage infection in some cultures

Answer 1

Answer - Option a) are induced by phage infection, but at different rates in different cultures.

Explanation - Spontaneous mutations may confer phage resistance by modifying the structure of bacterial surface components that act as phage receptors and that also determine phage specificity. This lead to  the number of resistant colonies per culture fluctuates (varies) between cultures: most yield a few resistant colonies, but some cultures had many. These results imply that mutations has taken place to phage resistance.