The Consequences of Mutation During the Growth of Biochemical Mutants of Escherichia Coli Iv

Ryan, Francis J.; Schneider, Lillian K.

doi:10.1128/jb.58.2.201-213.1949

Cited by 25 publications

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“…When between 100 and 400 colonies were present, however, their size was such that the total number of bacteria supported by the plate remained the same (ca 5 X 109). This is the number expected from work with histidine limitation in liquid cultures (Ryan and Schneider, 1949). Therefore, these colonies were limited in growth by the exhaustion of histidine, and h+ mutants arising among them might be expected to overgrow.…”

Section: Resultsmentioning

confidence: 93%

The Direct Enumeration of Spontaneous and Induced Mutations in Bacteria

1955

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Section: Resultsmentioning

confidence: 93%

The Direct Enumeration of Spontaneous and Induced Mutations in Bacteria

1955

Self Cite

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Evidence that inhibitor(s) are formed which may interfere with the growth of revertant colonies in the ames salmonella and the E. Coli tryptophan reverse mutation assays when strictly anaerobic conditions are used

Mortelmans¹,

Cox²

1992

Environ and Mol Mutagen

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Spontaneous and chemically induced revertant colonies were not observed on plates when a strictly anaerobic environment and anaerobically prepared media were used to perform the Ames histidine reversion assay with each of eight different Salmonella strains. A similar effect was observed when the E. coli tryptophan reverse mutation assay was performed under strictly anaerobic conditions. We provide evidence here that under anaerobic conditions growth inhibitor(s) are formed by the S. typhimurium and E. coli bacteria when the limited histidine and tryptophan, respectively, are depleted from the medium. The inhibitor(s) are nonspecific and inhibit the growth not only of prototrophic bacteria but also of the inhibitor-producing bacteria as measured by neutralized supernatants of growth-limiting minimal liquid cultures. Inhibitor(s) are also formed in stationary phase cultures of Salmonella and E. coli in minimal liquid medium supplemented with excess histidine and tryptophan, respectively. These results suggest that inhibitor formation under anaerobic conditions is a physiological phenomenon which interferes with at least two reverse mutation assays. Whether or not it also interferes with the reverse mutagenesis process remains to be determined.

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A simple approach for random genomic insertion–deletions using ambiguous sequences in Escherichia coli

Shekhar

Maeda

2022

J Basic Microbiol

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Escherichia coli K-12, being one of the best understood and thoroughly analyzed organisms, is the preferred platform for genetic and biochemical research. Among all genetic engineering approaches applied on E. coli, the homologous recombination approach is versatile and precise, which allows engineering genes or large segments of the chromosome directly by using polymerase chain reaction (PCR) products or synthetic oligonucleotides. The previously explained approaches for random insertion and deletions were reported as technically not easy and laborious. This study, first, finds the minimum length of homology extension that is efficient and accurate for homologous recombination, as 30 nt.Second, proposes an approach utilizing PCR products flanking ambiguous NNN-sequence (30-nt) extensions, which facilitate the homologous recombination to recombine them at multiple regions on the genome and generate insertion-deletion mutations. Further analysis found that these mutations were varying in number, that is, multiple genomic regions were deleted. Moreover, evaluation of the phenotype of all the multiple random insertion-deletion mutants demonstrated no significant changes in the normal metabolism of bacteria. This study not only presents the efficiency of ambiguous sequences in making random deletion mutations, but also demonstrates their further applicability in genomics. K E Y W O R D Sambiguous sequences, Escherichia coli, random genomic deletion, red recombination | INTRODUCTIONEscherichia coli, the most completely characterized single-cell life form, is a preferred model organism in bacterial genetic engineering research because of the available whole-genome sequence and described molecular genetics [1,2]. There are several methods available for genome-based engineering and to generate large mutant sets through both random and directed approaches [3][4][5]. Among all the reported approaches, homology-dependent, recombination-mediated, genetic engineering is considered as most efficient that allows engineering genes and segments of the bacterial chromosome directly by using polymerase chain reaction (PCR) products or synthetic oligonucleotides [6,7]. The E. coli KEIO mutant library is the best example of a directed

show abstract

The Consequences of Mutation During the Growth of Biochemical Mutants of Escherichia Coli Iv

Cited by 25 publications

References 18 publications

The Direct Enumeration of Spontaneous and Induced Mutations in Bacteria

The Direct Enumeration of Spontaneous and Induced Mutations in Bacteria

Evidence that inhibitor(s) are formed which may interfere with the growth of revertant colonies in the ames salmonella and the E. Coli tryptophan reverse mutation assays when strictly anaerobic conditions are used

A simple approach for random genomic insertion–deletions using ambiguous sequences in Escherichia coli

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