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S G Botina

Publications and source records attributed to S G Botina.

8 recordsLinked to original sources
PubMed2006

[Speciation in bacteria: comparison of the 16S rRNA gene for closely related Enterococcus species].

Sequencing of the 16S rRNA genes from enterococcal strains used as starters suggested the existence of specialized taxa of lactic acid enterococci within the species Enterococcus durans and E. faecium and a new species, E. lactis. Comparisons showed that the 16S rRNA genes of closely related species have the same sets of variable positions with different combinations of nucleotides. The presence of identical combinations of nucleotide substitutions in different species was assumed to result from a transfer of genetic information via gene conversion between different rRNA operons. Such events were presumably associated with speciation in bacteria.

Enterococcus↗
PubMed2001

[Homologous recombination and chromosomal rearrangements in Escherichia coli strains carrying a heterozygous tandem duplication].

Heterozygous tandem duplications formed in conjugational matings in Escherichia coli provides a convenient model system for studying the evolution of bacterial chromosome. Heterozygous duplications segregate various classes of haploid and diploid recombinants that appear as a result of unequal crossing over between sister chromosomes. In this work, an extended tandem duplication in the deo operon of E. coli carrying deoA deoB::Tn5/deoC deoD thr::Tn9 alleles was examined. Recombination between homologous DNA repeats in the duplication was studied in strains carrying different combinations of recBC, sbcBC, recB::Tn10, recQ::Tn3 mutations. The frequency of recombination between homologous DNA repeats was very high in all strains and did not decrease when the RecBCD and RecF recombinational pathways were simultaneously damaged in strains with the recB sbcBC recQ (or recF) genotype. It is assumed that unequal crossing over between direct DNA repeats in duplications may proceed through a particular pathway of "adaptive" recombination.

Alleles↗
PubMedDate not supplied

[Divergence in the level of DNA hybridization and formation of sibling species in the lactic acid bacteria Streptococcus thermophilus].

Previously, five distinct groups with 80-90% intragroup DNA homology values were revealed among 19 lactic acid-producing bacterial strains. The study of 39 new strains of thermophilic streptococci in the present work allowed us to reveal the sixth DNA homology group. The nine strains of this group are similar, at 55-70% DNA homology levels, to the type strain S. thermophilus ATCC 19258. Group VI showed a low level of DNA-DNA reassociation (20-30%) with the DNA homology groups I, II, III, and V. The intergroup DNA-DNA reassociation values determined from DNA renaturation rates varied from 20 to 50%. These data were interpreted as indicative of the existence of at least four sibling species among the thermophilic streptococci studied.

DNA, Bacterial↗
PubMedDate not supplied

[Comparison of genomes in Streptococcus thermophilus strains of different origins].

According to DNA hybridization data, thermophilic streptococci used in Russia as starters in the dairy industry are divided into 6 different genomovars, with a degree of DNA homology not exceeding 20-50%. The analysis of genomes from these genomovars using SmaI restriction endonuclease and pulsed-field gel electrophoresis revealed a wide variability of the genome size. In some strains, the genome size considerably exceeded 2000 kbp. Most of the strains studied contained plasmids about 120 kbp in size.

DNA, Bacterial↗
PubMedDate not supplied

[Elucidation of the taxonomic status of industrial strains of thermophilic lactic acid bacteria by sequencing of 16S rRNA genes].

Phenotypic characteristics and results of PCR tests for the presence of species-specific genes indicate that a number of strains of thermophilic lactic acid bacteria previously considered as belonging to Streptococcus thermophilus are actually closely related to enterococci. In the present study, partial (over 500 nucleotides) sequencing of 16S rRNA genes from 12 strains of thermophilic lactic acid bacteria used as starters for manufacturing sour milk products on the territory of the Commonwealth of Independent States (CIS) has been performed. According to the results of the sequencing, seven of the strains have been classified with Enterococcus durans. The earlier classification (based on PCR tests) of two of the strains as S. thermophilus and three of the strains as E. faecium has been confirmed. The data obtained demonstrate that the enterococci E. durans and E. faecium are widely used as thermophilic starters for manufacturing sour milk products on the territory of the CIS.

Base Sequence↗
PubMedDate not supplied

[The lactic acid enterococci Enterococcus faecium and Enterococcus durans: nucleotide sequence diversity in 16S rRNA genes].

Among the strains used as starters for making sour milk products on the territory of the CIS, the bacteria Enterococcus faecium and Enterococcus durans are frequently found. In this work, we studied a new collection of lactic acid enterococci and also obtained more complete data on the nucleotide sequences of 16S rRNA genes in some strains studied earlier and found that most strains had certain distinctions in their 16S rRNA genes as compared with the E. durans and E. faecium genes available in the NCBI database. Based on these data, it is suggested that the strains of lactic acid enterococci represent new, earlier unknown taxa of enterococci that use milk as an ecological niche.

Armenia↗
PubMedDate not supplied

[Isolation and identification of new nisin-producing Lactococcus lactis subsp. lactis from milk].

A method for isolating active nisin-producing strains of mesophilic lactococci was developed. Overall, 55 strains of mesophilic lactic acid bacteria were isolated from fresh cow's milk obtained from milk farms in various regions throughout Russia; of them, 36 displayed nisin-synthesizing activity. The three most active strains were studied according to morphological, cultural, physiological, and biochemical characteristics and identified as Lactococcus lactis subsp. lactis. The species attribution of the strains studied was confirmed by the similarity of the nucleotide sequences of the 16S rRNA gene. The nucleotide sequences of the 16S rRNA genes were deposited with the GenBank under accession numbers DQ255951-DQ255954. The distinctions between these strains in physiological and biochemical characteristics and the ranges of their bactericide action on the microorganisms capable of developing in agricultural materials and food products were determined. The isolated strains displayed considerably wider ranges of action, which differed from the nisin-producing strain MGU and the commercial nisin preparation (Nisaplin), used as a biological preserving agent.

Animals↗