Mutational property of newly identified mutagen l-glutamic acid γ-hydrazide in Escherichia coli

We previously found that an l-glutamine analog l-glutamic acid γ-hydrazide has high mutagenic activity through the high-throughput laboratory evolution of Escherichia coli. In this study, mutagenicity and mutational property of l-glutamic acid γ-hydrazide were examined by the Ames test and mutation accumulation experiments using E. coli. The Ames test revealed that l-glutamic acid γ-hydrazide showed higher mutagenic activity without metabolic activation than known mutagens 2-aminoanthracene, and cobalt(II) acetate tetrahydrate. This result indicates that l-glutamic acid γ-hydrazide does not require metabolic activation for mutagenic activity in E. coli. Mutation accumulation experiments and whole-genome sequencing analysis revealed the number and spectrum of the accumulated mutations with or without l-glutamic acid γ-hydrazide. In the presence of l-glutamic acid γ-hydrazide, MDS42 strain accumulated 392.3 ± 116.2 point mutations during 30 passages corresponding to 777 generations, while MDS42 strain accumulated 1.5 ± 2.5 point mutations without l-glutamic acid γ-hydrazide during 50 passages corresponding to 1341 generations. The mutational spectrum of l-glutamic acid γ-hydrazide was G/C to A/T transition (82.2 ± 4.3 %) and A/T to G/C transition (17.4 ± 4.3 %). These results indicated that l-glutamic acid γ-hydrazide has a strong mutagenic activity.