Mutants with Impaired Respiration in Staphylococcus afermentans

Mutants with small colonies and impaired respiration were induced by 5-fluorouracil in cultures of Staphylococcus afermentans, nctc 7503. The consumption of oxygen in colourless mutants attained 66-77%, and in mutants with orange colonies 68-77% of normal values. Inhibitors of protein synthesis (chloramphenicol, tetracycline, chlortetracycline), inhibitors of cell-wall synthesis (penicillin G, phenoxymethylpenicillin), as well as an inhibitor of RNA formation (actinomycin C) affected the growth of the parent and mutant staphylococci to the same extent. On the other hand, inhibitors which affect DNA—namely, degranol, myleran-mannitol and mitomycin C—selectively inhibited the growth of mutant staphylococci with impaired respiration. Mitomycin C induced irreversible depolymerization of DNA in bacterial cells; colourless mutants were 2·7-3·5 times, and mutants with orange colonies 33-45 times more vulnerable to its action than the parent culture. The extraction of DNA from bacterial cells showed that the capacity of DNA for extraction from a complex with proteins was decreased in colourless mutants by 2·8-2·9 times, and in mutants with orange colonies by 5·0-7·3 times.