[Characterization of enterobacteria producing the low-molecular-weight antibiotics microcins]. / Kharakteristika énterobakterii, produtsiruiushchikh mikrotsiny--nizkomolekuliarnye antibiotiki.

A comparative study of the morphological, cultural, physiological, and biochemical properties of the microcinogenic strains EcS 5/98, EcS 6/98, and EcB 214/99 with the known microcin C51 producer Escherichia coli M17(p74) showed that these strains belong to the species E. coli. The strains produced microcins with molecular masses lower than 10 kDa. Microcin biosynthesis was stimulated by a deficiency of nutrients in the cultivation media. Microcins were found to be resistant to thermolysin, but were degraded by pronase, protolichetrem, and the Bacillus mesentericus metalloproteinase. This indicated that microcins are peptides or contain peptides in their molecules. The study of cross immunity to microcins and the sequence of their genetic determinants showed that the microcins of strains EcS 5/98 and EcS 6/98 are of B type, whereas the microcin of strain EcB 214/99 presumably belongs to another type, since it suppresses the growth of the producers of C-type and B-type microcins. The new microcin producers possess antibacterial activity against natural isolates belonging to the genera Escherichia and Salmonella, against a wide range of colicinogenic Escherichia strains, and against the collection Salmonella cultures.

[Expression vector pLF22 for the lactic acid bacteria]. / Vektor pLF22 dlia ékspressii genov v molochnokislykh bakteriiakh.

The construction of the expression vector pLF22 for lactic acid bacteria is described. The vector contains a replicon of the cryptic plasmid pLF1311 from Lactobacillus fermentum and a multiple cloning site of the lacZ' gene integrated with the plasmid rep operon. Such a construction of the vector provides for the constitutive transcription of the cloned sequences lacking the terminators of transcription in all the strains that maintain the replication of the vector. The vector is suitable for a wide range of gram-positive and gram-negative bacteria, including probiotic strains. The efficiency of the vector was verified by expressing the beta-galactosidase gene in a laboratory Escherichia coli strain and the synthetic gene of somatotropin releasing factor (SRF) in the probiotic strains of lactobacilli and enterococci. A recombinant strain with the SRF gene included in the diet of laboratory animals exerted an effect on their physiological and anthropometric parameters and on the histological characteristics of animal tissues.

[A family of shuttle vectors for lactobacilli and other gram-positive bacteria based on the plasmid pLF1311 replicon]. / Semeistvo chelnochnykh vektorov dlia molochnokislykh i drugikh grampolozhitel'nykh bakterii osnovannykh na replikone plazmidy pLF1311.

A set of broad-host-range single-replicon shuttle vectors for cloning nucleotide sequences in gram-positive bacteria (lactobacilli, enterococci, lactococci, bacilli, etc.) was created. The vectors are based on the cryptic plasmid pLF1311 from Lactobacillus fermentum VKM 1311 belonging to a family of the sigma-type pE194-like plasmids. The vectors can replicate in gram-positive bacteria and Escherichia coli. They are stable in many gram-positive bacteria, have small sizes, and allow the selection of recombinants on media with X-Gal. The vectors that contain the region of initiation of the conjugal transfer of plasmid RP4 belonging to the incompatibility group IncP alpha can be mobilized in a great number of bacteria using a helper plasmid from E. coli but not from gram-positive bacteria.

The broad host range plasmid pLF1311 from Lactobacillus fermentum VKM1311.

The complete nucleotide sequence (2389 bp) of the cryptic plasmid pLF1311 from Lactobacillus fermentum VKM1311 was determined. DNA sequence analysis revealed the putative coding regions for a replicative protein (RepB), its repressor (RepA) and double-stranded (dso) and single-stranded (sso) origins. pLF1311 belongs to the pE194 family of rolling circle-replicating plasmids. A derivative of pLF1311 that contains the cat gene of plasmid pC194 of Staphylococcus aureus and the oriT of RP4 was constructed and transferred by conjugative mobilization from Escherichia coli to various Gram-positive bacteria. The stable maintenance of this derivative was shown in some strains of Lactobacillus, Lactococcus, Enterococcus and Bacillus under non-selective conditions.

[Cellulosolytic bacteria of the genus Ruminococcus from cattle rumen]. / Tselliulozoliticheskie bakterii roda Ruminococcus iz rubtsa korov.

Fifty-eight strains of cellulolytic cocci were isolated from the rumen of cows bred at different farms. These cultures were referred to Ruminococcus albus and Ruminococcus flavefaciens. Investigation of the rate of cellulose hydrolysis showed that the ruminococci were heterogeneous with respect to this parameter and could be classified into high-, medium-, and low-activity strains, hydrolyzing substrate in 50, 60-80, and 100 h, respectively. This rate was shown to be directly related (r = 0.69) to the capacity of ruminococci to adhere to the substrate.

[Biology of lysogenic strains of Streptococcus bovis and virulent mutants of their temperate phages]. / Biologiia lizogennykh shtammov Streptococcus bovus i virulentnykh mutantov ikh umerennykh fagov.

Three lysogenic streptococcal strains and four virulent mutants of temperate phages were studied. The bacterial strains proved to be close to the type strain of Streptococcus bovis in their morphological, cultural, physiological, and biochemical properties. Investigation into the interaction of the lysogenic cultures with virulent mutants of temperate phages showed that the culture age optimal for infecting was 3-5 h; intense lysis began in the second hour after infection and was virtually completed by the end of the third hour, i.e., the procedure of obtaining phages in HMT medium took 7-8 h. Phage titers in phage lysates varied from 3.93 x 10(10) to 11.25 x 10(10) active phage particles per ml; residual amounts of viable bacteria varied from 0.7 x 10(6) to 34.0 x 10(6) cells per ml. In liquid HMT medium, phage production by lysogenic cultures was not limited by 0.3% glucose or maltose, 0.5% peptone, or casein hydrolysate. Descriptions of virulent mutants VM 6/6, VM 32/6, VM 28/28, and VM 54/54 of temperate phages of Str. bovis are presented.

[Regulation of microbiologic processes in the rumen of ruminants by bacteriophages of Streptococcus bovis]. / Reguliatsiia mikrobiologicheskikh protsessov v rubtse zhbachnykh zhivotnykh bakteriofagami Streptococcus bovis.

Influence of bacteriophages of Streptococcus bovis on microbial activity in the rumen was investigated in experiments on cows. Main elements of the mechanism of bacteriophage action on the microflora have been detected. The daily feeding with bacteriophages results in productive infection of sensitive to them rumen bacteria and is associated with increasing bacteriophage concentration in the rumen contents, lower number and activity of amylolytic bacteria, higher cellolytic activity and increased number of bacteria utilizing xylan, cellobiose and xylose. The fermentation is usually shifted to a higher production of propionate and butyrate at the expense of lower acetate. The regulating action of a single bacteriophage feeding on the rumen microflora and its metabolic activity stops on the fifth day. Daily introduction of bacteriophages into the ration of cows under moderate or high levels of feed increases the milk fat by 0.1-0.3%.

Description of two anaerobic fungal strains from the bovine rumen and influence of diet on the fungal population in vivo.

Neocallimastix sp. NC71 and Piromyces sp. PC12 isolated from the calf remen grew optimally at 39 degrees C and pH 6.5-6.7, utilized a wide range of mono-, oligo- and polysaccharides and exhibited CMCase, Avicelase, cellobiase, amylase and xylanase activities. The end-products of wheat straw fermentation by both strains were acetate, formate, ethanol and lactate. The number of Neocallimastix sp. zoospores in the rumen of cows in the first 3 h after feeding with hay-silage-concentrate diets varied from 7 x 10(3) to 5.4 x 10(5) ml-1; the number of uniflagellate zoospores varied from 10(4) to 10(5) ml-1. Fungal zoosporgenesis and colonization of plant substrates in the rumen were induced by feed intake and were favoured by increased levels of crude fibre in the diet.

[Anaerobic cellulolytic fungi from cattle rumen]. / Anaérobnye tselliulozoliticheskie griby rubtsa krupnogo rogatogo skota.

Two anaerobic fungal strains, Neocallimastix sp. 71 and Piromonas sp. 12, were isolated from cattle rumen. Their motile zoospores have either one (strain 12) or several (strain 71) flagella. The spores get attached to a substrate, germinate and form a branched rhizoid with one sporangium within which a new generation of zoospores appears after 24 h, on the average. Both fungi have a temperature optimum at 39 degrees C and a pH optimum at 6.5-6.7. They can utilize a wide spectrum of mono-, oligo- and polysaccharides. Strain 71 produces acetate, formate, ethanol and lactate while strain 12 forms acetate, formate, lactate and traces of ethanol as main products accumulated upon the fermentation of wheat straw, filter paper and cellobiose in a liquid semidefined medium. Both strains exert the activities of CMCase, Avicelase, cellobiase, amylase and xylanase.

[Biological properties of Streptococcus bovis bacteriophages isolated from lysogenic cultures and sheep rumen]. / Biologicheskie svoistva bakteriofagov Streptococcus bovis, vydelennykh iz lizogennykh kul'tur i rubtsa ovets

Biological characteristics of eleven phages for Streptococcus bovis were investigated; seven phage were isolated from ovine rumen and four were virulent mutants of temperate phages of lysogenic cultures. The phages had many properties in common: similar morphology of negative colonies, the identical spectrum of lytic action, related antigens, absolute or high requirement of calcium ions, thermolability, and inactivation by the content of the rumen. Their susceptibility to the inactivating action of acetic acid, urea and temperature was however different. Chloroform and phenol may be used during purification and conservation of the phages.