Filament formation in E. coli induced by azaserine and other antineoplastic agents

Filament formation in radio-resistant mutants of Escherichia coli S after treatment with ultraviolet light and radiomimetic agents

Curry, Janet (Stanford Research Institute, Menlo Park, Calif.) and Joseph Greenberg. Filament formation in radioresistant mutants of Escherichia coli S after treatment with ultraviolet light and radiomimetic agents. J. Bacteriol. 83:38-42. 1962.-The effect of ultraviolet light and of five radiomimetic compounds on cell division, growth in liquid medium, and growth in solid medium of Escherichia coli S and four of its radioresistant mutants was examined. All of the agents, including ultraviolet light, induced filaments in the parent S and in at least one of its radioresistant mutants; two of the agents, azaserine and mitomycin C, induced filaments in three of the mutants; in only one mutant were no filaments induced by any agent. Growth in solid medium was more sensitive to the agents than was growth in liquid medium. The mutants differed among each other in their degree of resistance to most of the chemical agents, when inhibition of growth in agar was used as the criterion. There was no difference among the mutants in the dose of any agent required to inhibit overnight growth in liquid medium.

6-DIAZO-5-OXO-L-NORLEUCINE INHIBITION OF ESCHERICHIA COLI

Coggin, J. H., Jr. (The University of Chicago, Chicago, Ill.), and W. R. Martin. 6-Diazo-5-oxo-l-norleucine inhibition of Escherichia coli. J. Bacteriol. 89:1348-1353. 1965.-The glutamine analogue 6-diazo-5-oxo-l-norleucine (DON) induced filaments and spheroplasts in Escherichia coli during the transition of sensitive populations to a state of resistance. Resistance developed at a frequency suggesting mutant selection. The morphology of cells resistant to 100 mug of DON per ml was indistinguishable from that of sensitive cells. DON-resistant cells exhibited an extended growth lag when cultured in the absence of the drug. This extended lag could be reduced to the lag time of parent sensitive cells by a combination of d-glucosamine and inosine or by DON. Viable counts during the lag period of resistant cells indicate that this lag results from a decrease in the number of cells during the first 2 hr of incubation. A combination of d-glucosamine and inosine was required for complete prevention of the DON inhibition of sensitive cells. The results indicate that DON not only inhibits de novo purine biosynthesis but that it also prevents hexosamine synthesis and, ultimately, cell-wall synthesis in E. coli.

Azaserine: further evidence for DNA damage in Escherichia coli

Azaserine causes DNA damage in stationary-phase cells. In our investigation of this damage, we used strains of Escherichia coli differing in repair capabilities to study azaserine-induced DNA damage, detected as DNA strand breaks by sucrose gradient sedimentation techniques. Reduced sedimentation in alkaline and neutral sucrose gradients indicated the presence of both alkali-labile sites and in situ strand breaks. Azaserine induced DNA single-strand breaks (SSBs) abundantly in all but the recA strain, in which SSBs were greatly reduced. Treatment of purified DNA with azaserine from bacteriophages T4 and PM2 produced no detectable SSBs. Several other studies also failed to detect DNA damage induced directly by azaserine. Increased levels of beta-galactosidase were induced in an E. coli strain possessing a rec::lac fusion, providing further evidence for azaserine induction of the recA gene product. In addition, azaserine induced adaptation against killing but not against mutagenesis in wild-type E. coli strain.