[Lipid composition of Erysipelothrix rhusiopathiae and its L forms]. / Lipiden sustav na Erysipelothrix rhusiopathiae i polucheni ot nego L-formi.

Studied was comparatively the lipid composition of two strains of Erysipelothrix rhusiopathiae--A826-S and A973-S as well as the stable L-forms obtained from it and a form reverted back to the initial phenotypic state. All investigated organisms showed the presence of phosphatidylethanolamine, phosphatidyl-glycerol, cardiolipin, and small amounts of phosphatidylserine. Essential quantitative differences were found with cardiolipin which was about 25 per cent for the initial strains while its amount for the L-forms its amount reached 50 per cent and more. The reverted strain was shown to have a phospholipid profile close to that of the L-forms. Identified were 13 fatty acids with an even and odd number of carbon atoms as well as acids with double links. With both L-forms there was an increase in the amount of the lower fatty acids (up to C-15). A strong drop was observed of the palmitic acid (16:0). Discussed are the differences in the lipid composition of the L-forms with regard to their changed morphology and the capacity to survive without a cell wall.

[Nitrous acid induction of Escherichia coli mutants pathogenic for poultry]. / Indutsirane na mutanti ot Escherichia coli, patogenni za ptitsi, posredstvom azotista liselina.

Three strains of Escherichia coli - 0 78:K 80, 0 2:K 1, and 0 111: K 58, the first two pathogenic for birds - were used to test the mutagenic action of nitrous acid. Survival curves were drawn, and the optimal conditions were determined for the action of nitrous acid as a mutagenic factor. A scheme was suggested for the isolation of streptomycin-resistant and streptomycin-dependent mutants. The capacity of nitrous acid to induce mutations was demonstrated with regard to the streptomycin-dependence phenomenon and the rough (R) form of colonies. Discussed is the optimization of the streptomycin concentrations needed for the growth of the streptomycin-dependent mutants. Tested have been some biochemical activities of the mutants in comparison with the initial forms. It has likewise been demonstrated that the streptomycin-dependent mutants in R form change their reaction to some carbohydrate sources, either assimilating them at a delayed rate (as in most cases) or losing the capacity to assimilate them.

[Antibiotic relationship of streptomycin-dependent and streptomycin-resistant Escherichia coli mutants pathogenic for poultry]. / Otnoshenie na streptomitsinzavisimi i streptomitsinrezistentni mutanti ot Escherichia coli, patogenni za ptitsi, kum niakoi antibiotitsi.

Studied was the reaction streptomycin-dependent and streptomycin-resistant mutants and their revertants of the Escherichia coli strains 078:K80, 02:K1, and 0111:K58 to the following, practically important antibiotics: rifampicin, novobiocin, chloramphenicol, and penicillin. The study made use of mutants of both smooth (S) and rough (R) form obtained through induced mutagenesis effected by means of nitrosoguanidine and nitrous acid. The method of serial dilution of antibiotics and that of dynamic recording of their action through automatic biophotometry were employed. Negligible differences were established in the behaviour of the various groups of organisms. The streptomycin - dependent mutants retained unchanged the reaction of the initial strains to the antibiotics. The revertants showed high level of of resistance to streptomycin and by their behaviour they were closer to the streptomycin - resistant mutants than to the initial strains. In connection with this the probability is discussed of the "suppressor" origin of the streptomycin-dependent mutants.

[Growth characteristics of mutant strains of Escherichia coli isolated from poultry in the presence of streptomycin]. / Rastezhna kharakteristika na mutanti ot shtamove Escherichia coli, izolirani ot ptitsi v prisustvie na streptomitsin.

Three Escherichia coli strains--302(O111), 311(O78), and 331(O2) as well as streptomycin sensitive and streptomycin resistant mutants obtained from them by mutagenesis were studied. The sensitivity of all strains to streptomycin was tested in dilution series on hard and fluid medium. Growth curves were worked out by the biophotometer of Bonet, Maury and Jonan, adding various streptomycin concentrations to the medium at the very beginning of the experiment and 90 min after that. It was established that streptomycin concentrations above 15 microgram/cm3 added to bacteria sensitive to it at the beginning of their log-phase, shortens its duration by about 40%.