Question

Many bacteria, including E. coli, are capable of growing under both anaerobic (no oxygen) and aerobic (oxygen) Mutations are introduced into an E. coli strain that inactivate several enzymes involved in DNA repair (there are no other mutations). This mutant strain grows normally when kept in an incubator with a 100% nitrogen gas atmosphere. However, the strain dies when exposed to a normal laboratory atmosphere (oxygen). Why

Answer 1

It is reasonable to suppose that the mutations inactivate key enzymes involved in DNA repair during aerobic growth, but no mutations occurred in the genes that encode DNA repair enzymes required for anaerobic activity, thereby mutations are lethal in aerobic conditions. However, it is important to note that further experiments are needed to validate this hypothesis