Search

We studied chitin-glucan complexes from the soil micromycete Cephaliophora tropica D3. The yield and purity of chitin-glucan complexes depended on the medium used for micromycete culturing and the method of mycelium disintegration. Disintegration with liquid nitrogen allowed us to obtain preparations of chitin-glucan complexes with a low content of proteins and a high yield of chitosan (per dry fungal biomass unit weight).

Physiological and biochemical properties of the natural rhizospheric association of Klebsiella terrigena E6 and Bacillusfirmus E3 were studied. It was demonstrated that this association fixed actively molecular nitrogen at a rate of 110 nmol ethylene per 1 mg protein per h. The dynamics of bacterial population in the association and in pure cultures were studied. The properties of this association depended on the ratio of its components; the maximal nitrogen fixation was recorded at a content of B. firmus E310 amounting to 15% of the total cell number. It was demonstrated that the stability basis of this association was the specific interactions via its components via metabolites--phenol and para-hydroxybenzoic acid--as well as via nitrogen fixation, respiration, and pH of the medium. A scheme of the interactions between the components of association is shown.

Spontaneous mutants Km-R and Tc-R of R. japonicum with various levels of resistance to kanamycin (0.8-20 mg/ml) and tetracycline (130-210 micrograms/ml) were isolated. No cross resistance in the mutants was observed. Plasmid R68.45 transferred to the wild strains resistance to 210 micrograms/ml of tetracycline and to 20 mg/ml of kanamycin. This plasmid did not practically increase the resistance to tetracycline in mutants Tc-R. At the same time it markedly increased the resistance to kanamycin in mutants Km-R.

Mutations prv1, prv2 and mutR34, increasing frequencies of intragenic recombinations, are found not to complement and therefore to be alleles of one gene. Checking for the influence of mutator genes mutS3, mutT1 and uvrE502 on the intragenic recombination in conjugational crossings has shown that mutators mutS3 and uvrE502 increase the frequency of intragenic recombinations while mutT1 does not change it. None of the examined mutator genes influence the conjugational frequencies of recombination. A supplementary analysis for the mutability of the mutant prv1 has been carried out. The prv1 mutation can induce mutations of the frameshift type. Mutations uvrA6, recB21, recC22 and lexA produce no influence on the display of a mutator effect of the prv1 mutation.

The presence of 1-3 additional plasmids ranging from 16 to 400 Md in mol mass was revealed in bacterial cells besides a megaloplasmid in most of 34 Rhizobium meliloti strains studied. No correlation was found between plasmids pattern and geographical origin of isolation source of the strain analyzed.

In vitro repair of single strand breaks in T4 and phage DNA caused by 32p decay was studied. Zone centrifugation procedure showed that polynucleotide kinase, ligase enzyme system failed to repair 32P-damages. It was found that damaged DNA contained gaps and could be repaired by DNA-polymerase I, polynucleotide ligase treatment.

Using the trpA system of Yanofsky, it is shown that the mutator gene prv of Escherichia coli K-12 induces transitions in both directions (A:T in equilibrium G:C), and not A:T leads to leads to C:G and C:G leads to A:T transversions. The prv1 mutation was found to be recessive in prv+/prv1 merodiploid.

Plasmid pSUp2011 has been used to transfer transposon Tn5 into the cells of R. japonicum 110 and R. phaseoli 693. Transposition of Tn5 into the chromosomes of R. japonicum and R. phaseoli has been demonstrated,resulting in isolation of auxotrophic and symbiotic mutants of both strains. The frequencies of selected auxotrophic mutations have reached 4% in R. japonicum 110 and 0.6% in R. phaseoli 693. Streptomycin resistance gene locating on Tn5 has been found to be phenotypically expressed in R. japonicum 110 and R. phaseoli 693 cells.

The effect of several antibiotics on 4 rapid-growing Rhizobia, i. e. R. phaseoli, R. leguminosarum, R. trifolii and R. meliloti and 3 slow growing Rhizobia, i. e. R. vigna, R. japonicum and R. lupini was studied. It was shown that 4 of the species, i. e. R. meliloti, R. japonicum, R. vagna and R. lupini had multiple drug resistance. A tetracycline resistant mutant MC of R. japonicum was isolated.