Ultrastructural study of chitosan effects on Klebsiella and staphylococci.

Antibacterial effect of chitosan on the morphofunctional organization of clinical strains of Klebsiella pneumoniae and Staphylococcus aureus was studied by transmission electron microscopy. Chitosan promoted aggregation of bacterial cells and disorganization of bacterial cell wall and cytoplasmic membrane, which leads to the release of bacterial contents into the environment. These structural changes result in bacterial death.

[Antibacterial effects of water-soluble low-molecular-weight chitosans on different microorganisms]. / Antibakterial'naia aktivnost' vodorastvorimykh nizkomolekuliarnykh khitozanov v otnoshenii razlichnykh mikroorganizmov.

Low-molecular-weight chitosans with a viscosity-average molecular weight (Mv) of 5 to 27 kDa and equal degree of deacetylation (DD, 85%) were highly active against Pseudomonas aureofaciens, Enterobacter agglomerans, Bacillus subtilis, and Bifidobacterium bifidum 791, causing death of 80 to 100% of cells. An exception to this tendency was Escherichia coli, for which the rate of cell death, induced by the 5-kDa chitosan, was 38%. The antibacterial effect was manifested as early as 10 min after incubation of 12-kDa chitosan with B. subtilis or E. coli cells. Candida krusei was almost insensitive to the above crab chitosans. However, Candida krusei was highly sensitive to chitosans with Mv 5, 6, 12, 15.7, and 27 kDa: the minimum inhibitory concentration (MIC) varied from 0.06 to 0.005%. Chitosans with M, 5, 12, and 15.7 kDa exerted an antibacterial effect on Staphylococcus aureus. Chitosans with Mv 5, 15.7, and 27 kDa had no effect on Bifidobacterium bifidum ATCC 14893. The antibacterial effect of the 4-kDa chitosan on E. coli and B. bifidum 791 increased with DD in the range 55-85%.

[Search for biological remedies for fungi of the Candida genus]. / Poisk biologicheskikh sredstv protiv gribov roda Candida.

51 bacterial strains were studied with a view to find out anticandidial activity; of these, 15 strains were found to have activity, more on less expressed with respect to fungi of the genus Candida. In most cases the anticandidial activity of an antagonist strain was manifested to a similar degree against several Candida strains. The preliminary analysis of antifungal substances produced by microbial strains makes it possible to suggest their antibiotic nature.

[New shuttle-type vectors for cloning in Escherichia coli and Agrobacterium tumefaciens]. / Novye vektory chelnochnogo tipa dlia klonirovaniia v Escherichia coli i Agrobacterium tumefaciens.

The vectors capable of replication in Escherichia coli and Agrobacterium tumefaciens have been constructed on the basis of the plasmid pUB5502. The constructed vectors pVA12, pVA12-2, pVA12-4 contain the mini-replicon and trimethoprim resistance gene (Tp) of a broad host-range plasmid R388 (IncW). The pVA12 vector (8.8 kb) has been constructed by insertion of a kanamycin resistance gene (Km) from the plasmid pUC-4K into a Psti site. It possesses 7 unique restriction sites for XhoI, SmaI, PvuI, PvuII, HindIII, EcoRI, BamHI and the markers for kanamycin and trimethoprim resistance (Km and Tp). The pVA12-2 and pVA12-4 vectors were obtained as a result of changing of the PvuII-EcoI fragment of pVA12 carrying the Tp gene for the PvuII-EcoRI fragment of pBR322 carrying the Tc gene. These plasmids have the same size of 9.7 kb and 8 unique sites for restriction endonucleases XhoI, SmaI, PvuI, PvuII, EcoRI, EcoRV, SalI, BalI and Km and Tc genes. No difference has been registered between the two plasmids by restriction analysis, but pVA12-4 has the dramatically increased copy number in Escherichia coli cells. All three vectors are transferable to Agrobacterium tumefaciens with the same frequencies by transformation or conjugation and do not affect the oncogenicity of pTi.

[Range of the transmissivity of the genetic transfer factors pAP38, pAP39, pAP41 and pAP42]. / O diapazone transmissivnosti faktorov geneticheskogo perenosa pAP38, pAP39, pAP41 i pAP42.

A study was made of the transmissivity range of the genetic transfer factors pAP38, pAP39, pAP41 and pAP42 identified in E. coli. It was demonstrated that these factors are not capable of transfer to the cells of P. putida, P. fluorescens, R. leguminosarum, A. lipoferum, A. tumefaciens. Factor pAP42 is mobilized to transfer to P. putida and R. leguminosarum with the aid of plasmid RP4. It is assumed that in the course of mobilization, the cointegrative structures are formed between plasmids pAP42 and RP4.

[Genetic transfer of pAP38, pAP39, and pAP41 plasmids into E. coli, Erwinia, and Hafnia strains]. / Geneticheskii perenos plazmid pAP38, pAP39 i pAP41 v shtammy E. coli, Erwinia i Hafnia.

Genetic transfer factors pAP38, pAP39 and pAP41 can be transferred to E. coli, both typed and untypecd, as well as to Erwinia and Hafnia strains, with different frequency (10(-2) to 10(-8)). The transconjugates thus obtained possess donor activity and can transfer the factors they have received to recipient E. coli strains. After transfer these factors are stably maintained in a new host for at least 10 days. Under the action of ethidium bromide or elevated temperature the elimination of the transfer factors from host bacteria is observed. The studied transfer factors pAP38, pAP39 and pAP41 (F-like factors) are plasmids fi+.

Plasmid pEA566 from Erwinia aroideae.

A new plasmid designated pEA566 was isolated from Erwinia aroideae. The molecular weight of the plasmid, as determined by neutral and alkaline sucrose gradient centrifugation, electron microscopy, and agarose gel electrophoresis, was 6.6 X 10(6). The plasmid replicated under relaxed control, had three cleavage sites for KpnI restriction endonuclease, and no sites for EcoRI, BamHI, SalI, PstI, and HindIII.

[Properties of the bacteriocin of Erwinia aroideae]. / Svoistva bakteriotsina Erwinia aroideae]

Erwinicin, produced by Erwinia aroideae cells, consists of rod-shaped particles. The molecular weight of such particles, determined by the method of sedimentation in saccharose gradient, is 15 megadaltons. The size of the particles is 14 x 160 nm. The preparations of erwinicin are thermolabile, insensitive to the action of RNAase, pronase, DNAase and possess antigenic properties. The synthesis of erwinicin is an inducible process.

[F'ColVColBtrpcys plasmid in Erwinia aroideae]. / Plazmida F'ColVColBtrpcys v Er inia aroideae.

Erwinia aroideae carries a cryptic plasmid with 30 S sedimentation coefficient. Plasmid F'ColVColBtrpcys does not dissociate in E. aroideae and is replicated under stringent control since the number of plasmid copies per chromosome does not exceed one. The behaviour of F'ColVColBtrpcys plasmid in E. aroideae is characterized by (1) instability observed at both spontaneous and after EB treatment, (2) depression of plasmid genes that determine colicin synthesis.

[Localization of Rsf- mutation in Escherichia coli HfrC7]. / Lokalizatsiia mutatsii SVR- v Escherichia coli HfrC7.

The contransduction frequency of MAAs, UVs phenotype of Escherichia coli HfrC7 and its 7-51F- derivative with purE markers is found to be 1-2% which indicates that the mutation N 7 is located close to the F integration site in HfrC strain. E. coli strains K-12 7-51F+ and 7-51ColV2+ transfer chromosome markers in the same direction as does HfrC strain. The results suggest the presence of an integrated F fragment (sfa locus) into K-12 7-51F- chromosome.