FILAMENT FORMATION AND RESISTANCE TO 1-METHYL-3-NITRO-1-NITROSOGUANIDINE AND OTHER RADIOMIMETIC COMPOUNDS IN ESCHERICHIA COLI

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.

Effect of aflatoxin B-1 on the proteolytic activity of some lactic-acid bacteria

The proteolytic activity of five (ATCC) strains of lactic acid bacteria were investigated in the presence of different concentrations of aflatoxin B-1. The presented data revealed that aflatoxin in milk can affect the lactic acid bacteria which are used in the manufacture of dairy products. Such effect depends on toxin concentration and the species of lactic acid bacteria. This investigation is of practical value because it may explain the effect which occurs during cheese manufacture. This defect can be characterized by off flavour which can be very undesirable for a ripened cheese.

Antimicrobial evaluation of 1-methyl-3-nitro-1-Nitrosoguanidine

1-Methyl-3-nitro-1-nitrosoguanidine was shown to have in vitro antimicrobial activity against fungi and gram-positive and gram-negative bacteria; it was also shown to have in vivo activity in mice experimentally infected with Staphylococcus aureus or Escherichia coli comparable to that observed with penicillin or streptomycin sulfate.

Enhancement of Agrobacterium tumefaciens infectivity by mitomycin C

The ability of Agrobacterium tumefaciens to induce pinto leaf tumors may be enhanced two- to threefold after treatment with mitomycin C. The enhancement may be obtained with either lethal or nonlethal concentrations. With 10-min treatments, an optimal response was obtained with 0.005 mug of mitomycin C per ml in the absence of any change in the number of viable cells. Both the tumor induction process and the tumors induced by treated cultures appear qualitatively the same as controls. To account for these results, the antibiotic must increase the proportion of viable cells that will subsequently initiate tumors. One, or at most a few, random lesions in the bacterial chromosome seem to be the necessary requirement for this promotion. At mitomycin concentrations of 1 and 5 mug/ml, the ability of A. tumefaciens to initiate tumors is rapidly lost, indicating that a fairly intact bacterial chromosome is one of the essentials for the tumor induction process.