Complete Genome Sequences of the Probiotic Lactic Acid Bacteria Lactobacillus helveticus D75 and D76.

Lactobacillus helveticus D75 and D76 were isolated from the intestinal tract of a healthy child. Both strains possess symbiotic, probiotic, and antagonistic activities. We have sequenced and annotated the whole genomes of L. helveticus D75 and D76 and have conducted a preliminary genome comparative analysis.

IDENTIFICATION OF BACTERIOCIN GENES IN PROBIOTIC STRAINS OF LACTIC ACID BACTERIA LACTOBACLLUS ACIDOPHILUS D-75 AND LACTOBACILLUS ACIDOPHILUS D-76.

AIM: to detect the bacteriocin genes of probiotic strains Lactobacillus acidophilus 0-75 and Lactobacillus acidophilus D-76 (components of Vitaflor dietary supplement). MATERIALS AND METHODS: The antagonistic activity of L. acidophilus D-75 and L. acidophilus D-76 strains was estimated by the deferred antagonism method. The identification of bacteriocin genes was performed by PCR using helveticin J gene primers. Amplified fragments were sequenced using ABI PRISM' 310 Genetic Analyzer and were analyzed using NCBI/BLASTX. RESULTS: The test bacteria exhibit pronounced antagonistic activity (AA) against Escherichia coli 075 and Salmonella Enteritidis 209. In the presence of Actoflor-S (metabiotic dietary supplement) the antagonistic activity of tested probiotic strains was 2-2.5-fold increased indicating its inducible nature. The identical sequences of 537 bp homologous to gene fragment of helveticin of L helveticus DPC457l (hv_1632 gene) were detected in DNA of both strains. Sequencing of these fragments showed difference in three nucleotides.compared to the reference DNA of DPC4571 strain (A instead of G at position 46, C instead of T at position .249 and A instead of T at position 537), but all these replacements do not lead to changes in the amino acid sequence of a bacteriocin. For L acidophilus D-76 another bacteriocin gene fragment of 283 bp was identified (in addition to 537 bp fragment). The latter had 95% homology with the helveticin J gene of L helveticus R0052 (R0052_09025 . gene). In NCBI/BLASTX database the sequences homologous to the helveticin gene of L. helveticus DPC4571 were found in 11 microorganisms related to L. acidophilus, L. amylovorus, L. crispaus, L gallinarum, L. helveticus and L. kitasatonis. CONCLUSION: Thus, our study shows that there are at least two bacteriocins in L. acidophilus D-76 and one bacteriocin in L. acidophilus D-75. However, the true potential of these probiotic bacteriocins for human health has yet to be releized.

[Release of protein into the extracellular space as a nonspecific response to stress in Escherichia coli]. / Vydelenie belka vo vnekletochnoe prostranstvo kak nespetsificheskaia reaktsiia Escherichia coli na stress.

This paper is concerned with the kinetics of excretion of fluorescent tryptophan-containing proteins from Escherichia coli cells kept in physiological saline at room temperature or incubated at 42, 48, and 55 degrees C. The kinetic curves of the extracellular concentration of protein can be described by parameters T and C, where C is the stationary extracellular concentration of the protein and T is the time in which the given concentration is reached. T was found to be a variable, and C was a constant independent of the type and strength of the stress. During the protein release, the viability of the cells was maintained at the initial level, but, after the concentration of the protein reached a stationary value, the culture cells died exponentially. All this allows the protein release into extracellular medium to be considered as a nonspecific response of E. coli to stress. The protein excretion was analyzed with reference to the data on the kinetics of release of other UV-absorbing compounds from the cells.

[Spectrofluorometric analysis of Escherichia coli during storage in a physiological solution]. / Spektrofluorimetricheskii analiz Escherichia coli v protsesse khraneniia v fiziologicheskom rastvore.

Escherichia coli cells were kept in a physiological solution at room temperature. The fluorescence of aqueous suspensions of the cells and the medium was recorded every day. Inactivation of the culture was found to be accompanied with the appearance in the medium of protein and non-protein fluorescent metabolites. The coefficient of correlation between the quantity of living cells and the intensity of fluorescence emitted by the non-protein component had a negative sign and differed reliably from zero. The authors discuss the nature of non-protein fluorescence and what made the cells die off in the process of storage.