Chemical and UV mutagenesis in Zymomonas mobilis

Mutagenesis of the facultative anaerobe Zymomonas mobilis was accomplished by three different mutagens. Ultra-violet (UV) irradiation, whose effectiveness relies on misrepair of damaged DNA via an error-prone pathway, was a poor mutagen for this organism. Ethyl methane sulphonate (EMS) gave results very similar to UV-irradiation. N-methyl-N-nitro-N-nitrosoguanidine (MNNG), which is believed to act by multiple mutagenic mechanisms, was the most powerful mutagen, always resulting in a large number of mutants of all types examined (i.e. auxotrophs, antibiotic resistant, heavy metal resistant and ultraviolet sensitive). Reversion frequencies of MNNG-induced mutants were very low. Evidence is provided that mutagenesis of Z. mobilis is affected by photoreactivation, adaptive response and error-prone repair mechanisms. Moreover, cells treated with alkylating agents and allowed to recover under anaerobic conditions clearly demonstrated that anaerobiosis plays a significant role in repair, but not in the induction of mutants.