In mutant strains ofBrevibacterium sp. M27 requiring amino acids and resistant to antibiotics four methods were verified and a method inducing a high formation of protoplasts and their reversion was developed. Formation of protoplasts is 60–99% and their reversion 17–76%. In induced mutants a correlation between protoplast formation and growth rate could be demonstrated.

Inducible pigmentation changes were observed in pigmented strains ofBrevibacterium sp. M27 andB.flavum treated with N-methyl-N’-nitro-N-nitrosoguanidine. The highest frequency of induction was reached already at a survival of 30–40% with the maximal yield of 6–10%. As compared with the initial yellow colour, three new pigmentation types,viz. white, pink and orange, were observed. The yellow pigmented parent strains are most resistant to the lethal effects of UV radiation. By selecting pigmented mutants of all types on media containing antibiotics it was possible to obtain strains that were resistant either to tetracycline or to streptomycin. Auxotrophic pigmented mutants were also isolated. In multiple mutant strains ofBrevibacterium sp. M27 a number of strainsexhibited a changed L-lysine production. In some strains the production was variable, whereasother strains did not producel-lysine at all and strains with a limited production of other amino acids were also detected.

Conditions under which it is possible to induce auxotrophic mutants and DL-selenomethionine-resistant mutants inB. flavum by N-methyl-N’-nitro-N-nitrosoguanidine were determined. The yield of auxotrophic mutants was increased to 3% during mutagenesis in the first stage and to 1.5% in the second stage when using the enrichment-selective method with vancomycin. The optimal vancomycin concentration for inactivation of prototrophic cells growing in a minimal medium was 200 mg/L and the optimal time of treatment was 8 h. When testing the effect of three amino acid analogues (dl-ethionine,dl-selenomethionine and L-methionine sulfoximine) it was found thatB. flavum is sensitive todl-selenomethionine present in the minimal cultivation medium. Mutants resistant to 1 mg/mL of selenomethionine were isolated. Both isotope studies and measurement of growth indicate thatdl-ethionine also entersB. flavum cells, although its competition with endogenously synthesized methionine is not significant.

The optimum eonditions for the induction of mutants resistant to antibiotics inBrevibacterium flavum ATCC 14067 were determined. UV irradiation at the energy fluence of 6.5 kJ/m2 and N-methyl-N’-nitro-N-nitrosoguanidine (1 mg/mL) at pH 6.0 were used for the induction of mutants. Mutant strains resistant to rifampicin, oleandomycin, streptomycin and erythromycin were prepared.

Byla studována mutageneze kmene Brevibacterium sp. M-27 pomocí N-methyl-N´-nitro-N-nitrosoguanidinu s cílem připravit nové producenty L-lysinu a dalších aminokyselin. Výsledkem práce je soubor autotrofních kurantních kmenů, pigmentovaných a autotrofních pigmentovaných mutant. Byli získáni suspektní producenti alaninu, valinu a kyseliny glutamové. Mezi mnohonásobně depedentními mutantami existují kmeny se zvýšenou produkcí L-lysinu.

A positive genetic transfer by protoplast fusion was obtained in auxotrophic mutantsBrevibacterium sp. M27his andBrevibacterium sp. M27arg. Transformation and protoplast fusion with liposomes (as genetic transfers in intact cells and their protoplasts by both the chromosomal and plasmid DNA) did not lead to transfer of the markers followed.

Formation of protoplasts and their reversion were followed in 7 strains of brevibacteria. The formation of protoplasts and their reversion differed both between various species of brevibacteria and between various mutant strains of the same species.

A method using vancomycin for the accumulation of auxotrophic mutants ofMycobacterium smegmatis M54/81 induced by N-methyl-N′-nitro-N-nitrosoguanidine was developed. As compared with the simple replication technique the yield of auxotrophic mutants was twenty-fold.

The mutation range was studied inBrevibacterium sp. M27 after UV irradiation and after treatment with N-methyl-N’-nitro-N-nitrosoguanidine. The induction of auxotrophic mutants and mutants resistant to streptomycin and tetracycline was investigated. A collection of auxotrophic mutants for the studies of genetic transfer in this model was prepared.

Osmotically fragile cells ofBrevibacterium sp. M 27 were obtained after treatment with lysozyme and penicillin. These forms were detected by optical and electron microscopy.

A total of 40 substances were tested for their inhibitory effect on the multiplication of a bacteriophage in a growing culture ofBacillus licheniformis and their influence on bacitracin production. Acriflavine was the only substance which, at a concentration of 3 μg ml-1, completely suppressed phage multiplication while having no effect on the growth ofBacillus licheniformis and on the production of the antibiotic.

Four non transformable mutants ofBacillus subtilis 168 defective in the penetration of DNA into the recipient cell were isolated. All mutants were fully non-transformable with mutations in genes influencing irreversible binding of the donor DNA by the recipient cell.

Of several chemicals tested on the elimination of plasmids fromEscherichia coli K-12, the compound designated ICR-170 was most effective, applied at 100 μg/ml, the effect being comparable to that of acriflavin. It had no effect on the elimination of the R1 plasmid fromEscherichia coli JC 5455.

The inhibitory effect ofd-glucosamine andd-galactosamine on the induction of competence inStreptococcus Wicky was detected. These sugars also inhibited the transformation inBacillus subtilis 168trp 2 − . The same effect was observed inBacillus subtilis when usingN-acetyl-d-galactosamine.