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Biomedical subjects

J Konícek

Publications and source records attributed to J Konícek.

At least 19 recordsLinked to original sources
PubMed1992

The possibilities of changing the production of exocellular polysaccharides of a mutant Mycobacterium strain.

By second-step mutagenesis and treatment with N-methyl-N'-nitro-N-nitrosoguanidine a mutant strain of Mycobacterium sp. V-649 producing a glucan extracellular polymer and another new streptomycin-resistant mutant were prepared. This mutant strain formed more than 100% first-rate (1.0-1.2%) exocellular polysaccharide. Treatment with 1% dimethyl sulfoxide during submerged cultivation of the mutant strain did not increase the production of the extracellular polysaccharide.

Culture Media↗
PubMed1992

Use of whey for production of exocellular polysaccharide by a mutant strain of Xanthomonas campestris.

Growth and kinetics of the production of exocellular polysaccharide was studied in a mutant strain of Xanthomonas campestris lac+ during cultivation in a submerged culture in a medium containing whey. The maximum production of the polymer was observed at the initial stage of the stationary growth phase of the culture. The mean production yield was about 1.4%. The results were comparable with those obtained during cultivation on a lactose medium.

Animals↗
PubMed1991

Composition of intracellular soluble proteins in Mycobacterium "rubrum" and its mutants.

The composition of intracellular soluble proteins in a parental strain of Mycobacterium "rubrum" and its mutants was studied by polyacrylamide gel gradient electrophoresis. The composition of the protein fractions of the parental and the mutant strains was similar, they differed in one protein only. The presence of a 60 kDa protein should be stressed since its increased amount may be connected with a different intensity of the production of pigments in the strains studied.

Bacterial Proteins↗
PubMed1991

Gene manipulation in mycobacteria.

Gene manipulation in mycobacteria developed in two phases. In the first phase genes of mycobacteria were transferred into cells of E. coli and Streptomyces lividans. In the second phase, heterologous genes were transferred into mycobacteria either with a shuttle plasmid or hybrid plasmids. A prerequisite for successful gene manipulation in mycobacteria was a thorough understanding of plasmids in mycobacteria. Construction of recombinant DNA molecules contributed not only to the fact that mycobacteria did not remain outside the mainstream of modern genetic research but also to their present practical importance.

Escherichia coli↗
PubMed1990

Production and characteristics of the exocellular polysaccharide of a mutant Mycobacterium strain.

Mutant strains of Mycobacterium sp. V-649 producing highly mucous colonies on a solid cultivation medium were prepared after treatment with N-methyl-N'-nitro-N-nitrosoguanidine and production of the exocellular polysaccharide was tested. The strains were cultivated in media with suitable sugar sources under submerged conditions. It was found that Mycobacterium sp. V-649/15 produces a maximum of 15-19% polymer after a 5-6-d cultivation. Gas chromatography indicated that the exocellular polysaccharide produced by this strain is of glucan type.

Chromatography, Gas↗
PubMed1988

Pigmentation changes in brevibacteria induced by mutagenic treatment.

Inducible pigmentation changes were observed in pigmented strains of Brevibacterium sp. M27 and B. 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 of Brevibacterium sp. M27 a number of strainsexhibited a changed L-lysine production. In some strains the production was variable, whereasother strains did not produce L-lysine at all and stains with a limited production of other amino acids were also detected.

Brevibacterium↗
PubMed1988

Mycobacteria in the light of modern genetics development.

It is generally assumed that genetic research of mycobacteria is delayed as compared with other, more commonly used, bacterial models, particularly in the field of genetic transfers. In the field of mutagenesis the problems have been studied to such an extent that replication maps of the chromosome of M. phlei and M. tuberculosis H37 Rv have already been constructed and a new model of the cell cycle of bacteria exhibiting a slow growth rate has been worked out. When the problems of mycobacterial genetics are looked upon in the light of gene manipulations it may be concluded that mycobacteria belong to a few models whose genes are used for cloning and that problems of practical significance will be studied by means of the most modern approaches.

Genetics, Microbial↗
PubMed1986

Induction of mutants resistant to antibiotics in Brevibacterium flavum.

The optimum conditions for the induction of mutants resistant to antibiotics in Brevibacterium 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.

Anti-Bacterial Agents↗
PubMed1986

Genetic transfers in Brevibacterium sp.

A positive genetic transfer by protoplast fusion was obtained in auxotrophic mutants Brevibacterium sp. M27 his and Brevibacterium sp. M27 arg. 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.

Brevibacterium↗
PubMed1984

Cell cycle in Mycobacterium phlei.

The initial replication region of the chromosome on the replication map of M. phlei constructed by means of sequential mutagenesis in synchronous populations was accurately determined. By following the time shift of the replication moment of the genes bac and met in the control culture and in the culture with the initial inhibition of DNA synthesis by nalidixic acid the start of replication of the chromosome was determined at 15 min before replication of the gene ile. On the basis of the results obtained a scheme of the cell cycle in M. phlei was proposed. Intervals C and D depend on the generation time, become prolonged independently of each other and assume the whole cycle. The ratio C/(C + D) equals to 0.56 and the interval D has a value of 0.76 of the interval C. The mutual ratio of the intervals C : D is 1.3 : 1.0. The obtained results make it possible to form the assumption about mutual ratios between the chromosome replication and cell division in bacteria exhibiting slow growth rates.

Cell Cycle↗
PubMed1981

The completion of the replication map of the Mycobacterium phlei chromosome.

New facts about the replication map of Mycobacterium phlei chromosome are summarized. Replication positions of two genes located in marginal regions of the replication map, ile close to the origin and ser near the terminus, were determined. Known positions of replication of some genes were defined with more precision within 2.5--5-min intervals using the method of sequential mutagenesis in synchronized cultures (leu, met, bac, pyr, stm, tet, cyc, his). Replication positions of genes responsible for the biosynthesis of thiamine and resistance to tetracycline and vancomycin were further identified. The contemporary replication map contains replication positions of 24 genes.

Chromosome Mapping↗
PubMed1981

Mutagenic effect of n-methyl-N-nitrosourea on Mycobacterium phlei.

N-Methyl-N-nitrosourea was used to induce auxotrophic, scotochromogenic and isonicotinic acid hydrazide resistant mutants in Mycobacterium phlei and its effect was compared with that of nitrosoguanidine. Seventeen auxotrophic mutants requiring amino acids or vitamins and 52 scotochromogenic mutants with orange colonies were induced. The frequency of isonicotinic acid hydrazide-resistant mutants increased by two orders of magnitude.

Amino Acids↗
PubMed1981

Use of nalidixic acid for constructing the replication map of the Mycobacterium phlei chromosome.

Nalidixic acid was used for describing more accurately the terminal replication region of the Mycobacterium phlei chromosome. Cell division in synchronized cultures was not sensitive to this acid any more between 185-190 min, i.e. about 10 min after replication of the ser gene, the last of 24 genes of the replication map described so far. The replication of the chromosome was controlled by determining the position of the bac gene. Microscopic studies in phase contrast of the cells that were subjected for long time periods to nalidixic acid treatment at a bactericidal concentration showed elongated cells. The electronmicroscopic observation showed that a portion of the population influenced by nalidixic acid lyses, whereas other cells remain intact and resemble control cells.

Cell Division↗
PubMed1978

The replication map of the chromosome of Mycobacterium phlei.

It was the aim of the present work to construct the replication map of the chromosome of Mycobacterium phlei. The method of mutagenesis of the replication point by N-methyl-N-nitroso-N'-nitroguanidine in synchronously dividing populations and the method of analysis of gene frequency were applied. The order of replication of 19 genes on the chromosome was determined by means of induction of back mutations and forward mutations in auxotrophic mutants PA leu and PA met and in double auxotrophic mutants with methionine as a reference marker.

Chromosome Mapping↗