Abstract
Over 60 years ago, researchers started the genetic analysis of bacterial cell division by isolating conditional, temperature-sensitive mutants of essential Escherichia coli cell division genes. These early mutants were obtained by mutagenesis with chemical agents that introduced dozens to hundreds of mutations in the bacterial genomes. In this work, we present the complete genome sequences of six of these original mutants on ftsA, ftsZ and ftsQ genes, along with two of the strains used to generate them. The genomes of mutants obtained by exposure to nitrosoguanidine had 100 to 400 mutations. Transducing target alleles into a new strain effectively reduced the number of mutations, but those near the target gene were co-transduced with it. In contrast, a mutant generated by site-directed mutagenesis maintained the genomic background intact. The genomic analysis improves our understanding of these foundational strains, offering insights into the effects of historical mutagenesis techniques. These findings underscore the importance of genomic characterization in ensuring accurate interpretations of experimental results in microbiological research.