RESISTANCE AND CROSS-RESISTANCE OF ESCHERICHIA COLI MUTANTS TO ANTICANCER AGENTS. 1-METHYL-3-NITRO-1-NITROSOGUANIDINE

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.

Isolation of mutants of Escherichia coli with increased resistance to alkylating agents: mutants deficient in thiols and mutants constitutive for the adaptive response

A search has been made for mutants of E. coli that are constitutive for the adaptive response to alkylating agents. When selection was for resistance to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) the resulting strains all proved to be low in intracellular thiols. As MNNG has to be converted by thiols to the proximal mutagen methylnitrosamine, these strains were resistant simply because their low thiol levels made them less readily methylated by MNNG. The selection was therefore undertaken for strains resistant to N-methylnitrosourea (MNU) because this alkylating agent does not require activation by thiols. Four MNU resistant mutants proved to be constitutive for the adaptive response. Following exposure to (3H) MNNG, they showed the same low ratio of O6-methylguanine (O6MeG) to 7-methylguanine (7MeG) as adapted wild type bacteria. The ratio of 3-methyladenine (3MeA) to 7MeG was the same in the wild type, the adapted wild type, and the constitutive strains. When exposed to very high MNNG doses, the constitutive mutants were even more resistant to mutation and killing than the adapted wild type. They have an even greater ability than the adapted wild type to remove O6MeG from methylated DNA (Lindahl personal communication).

Mutations determining mitomycin resistance in Bacillus subtilis

Iyer, V. N. (Microbiology Research Institute, Canada Department of Agriculture, Ottawa, Canada). Mutations determining mitomycin resistance in Bacillus subtilis. J. Bacteriol. 92:1663-1669. 1966.-The pattern of development of genetic resistance in Bacillus subtilis to mitomycin C was studied, and spontaneous single and multistep mutants were obtained. The transmission and expression of these mutations in sensitive strains proved possible by means of genetic transformation. The mutations were genetically studied in relation to a chromosomal mutation, mac-1, which confers resistance to the macrolide antibiotic erythromycin and which has been previously localized in the early-replicating segment of the B. subtilis chromosome. The results indicate that all of three primary mutations studied in this manner, as well as a secondary and tertiary mutation derived from one of the primary mutations, are clustered in this early-replicating segment. It appears that the secondary and tertiary mutations enhance the resistance conferred by the primary mutation, apparently without themselves conferring any resistance.

Cross-resistance relationships in Escherichia coli between ultraviolet radiation and nitrous acid

Zampieri, Antonio (Palo Alto Medical Research Foundation, Palo Alto, Calif.), and Joseph Greenberg. Cross-resistance relationships in Escherichia coli between ultraviolet radiation and nitrous acid. J. Bacteriol. 87:1094-1099. 1964.-A number of radiosensitive and radioresistant strains of Escherichia coli were tested for sensitivity to injury by nitrous acid. All the radioresistant strains, including 13 radioresistant mutants of strain S, B/r, Bpr5, and K-12, were found to be significantly more resistant to nitrous acid than were the radiosensitive strains S and B. The radioresistant mutants of strain S, Bpr5, and K-12 displayed similar responses to nitrous acid and were less resistant than was strain B/r. Strains B and S were indistinguishable on the basis of nitrous acid sensitivity. The survival curves of all strains examined were similar in shape to corresponding survival curves after ultraviolet radiation. The sensitivity to nitrous acid of the radiosensitive strains S and B, but not that of the radioresistant strains, was found to be greater on Tryptone medium than on Penassay medium, and greater on Penassay medium than on glucose-salts medium. Between 2 and 3% of the strain S survivors of nitrous acid treatment were radioresistant; 46 such radioresistant mutants were isolated and found to be identical in cross-resistance pattern with radioresistant types (R(3), R(4), or R(6)) previously described. The proportions in which these radioresistant types were found to occur were similar to those observed after selection by other radiomimetic agents.

RESISTANCE AND CROSS-RESISTANCE OF ESCHERICHIA COLI S MUTANTS TO THE RADIOMIMETIC AGENT PROFLAVINE

Woody-Karrer, Pearl (Palo Alto Medical Research Foundation, Palo Alto, Calif.), and Joseph Greenberg . Resistance and cross-resistance of Escherichia coli S mutants to the radiomimetic agent proflavine. J. Bacteriol. 87: 536–542. 1964.—All 50 of the first-step mutants of Escherichia coli S selected for resistance to proflavine were resistant to ultraviolet light and each of five different radiomimetic chemicals. The mutants were classified into eight types on the basis of their relative resistance to six different radiomimetic drugs and on the basis of the shape of their ultraviolet survival curves. Three of these types are identical to types previously isolated with other radiomimetic drugs; five of the types are new. A high proportion of the clones surviving proflavine treatment were phenotypically but not genetically resistant, and no strains were isolated which were resistant to proflavine but were not resistant to radiation.

RESISTANCE AND CROSS RESISTANCE OF ESCHERICHIA COLI S MUTANTS TO THE RADIOMIMETIC AGENT NITROFURAZONE

Woody-Karrer, Pearl (Palo Alto Medical Research Foundation, Palo Alto, Calif.) and Joseph Greenberg . Resistance and cross resistance of Escherichia coli S mutants to the radiomimetic agent nitrofurazone. J. Bacteriol. 85: 1208–1216. 1963.—Cross-resistance relationships are described for 73 mutants of Escherichia coli strain S selected in one step for resistance to nitrofurazone. The test agents included ultraviolet radiation, five radiomimetic compounds, and penicillin; 12 different types of mutants could be selected. Two of these were chemoresistant, three were identical to radioresistant types previously isolated by use of other radiomimetic agents, and seven represented previously unobserved radioresistant types. The majority of radioresistant strains did not respond to plating-medium reactivation after ultraviolet radiation, despite the ultraviolet radiation responses of several minority representative strains. The data presented indicate that radioresistance in E. coli S does not involve resistance to most toxic agents; on the other hand, cross resistance to radiomimetic compounds is not restricted to alkylating agents.