Catastrophe and what to do about it if you are a bacterium: the importance of frameshift mutants.

Key problems that bacteria have historically faced are the challenges of the lack of essential nutrients and the presence of antibiotics produced naturally, but there are many other challenges. It appears that for many of these challenges the bacteria have mechanisms encoded in their genomes that are not usually functioning, but may be "turned on" when needed, even if the need only occurs once in hundreds of thousands of generations. Such mechanisms at other times somehow need to be "turned off" because they may cause a slight disadvantage, or even a grave disadvantage to the cell compared with wild-type cells during the time the population is not being challenged. On the other hand, a gene cannot simply be discarded because it might be needed again. How do microorganisms solve the problem of responding to challenges that only occur rarely? I suggest that in most cases, the mutation must occur by the existence of a readily reversible mutation. The mutation in likely the result of a frameshift mutation that caused the response and later another frameshift occurs to return the genome to its original state.