S. Dimov

GENETICS OF BACTERIOCINS BIOSYNTHESIS BY LACTIC ACID BACTERIA

Many studies have been focused on bacte-riocins produced by lactic acid bacteria (LAB), especially those produced by many dairy starter cultures strains because of their potential industrial application as natural food preservatives. Bacteriocins are toxins with protein nature that are riboso-mally synthesized by gram-positive bacte-ria and excreted out of the cell. They can be divided into 4 major classes: Class I, lantibiotics (1) (containing posttranslatio-nally modified amino acids such as lan-thionine and β-methyllanthionine); Class II – small unmodified thermo stables usually positively charged at a neutral pH peptides (2); Class III – large unmodified thermo labile peptides (3), and Class IV – complex bacteriocins which possess a carbohydrate or lipid component (4). Most of the inves-tigations were focused on the protein na-ture of bacteriocins, nevertheless in the last years many data were accumulated regar-ding the genetic determinants of bacte-riocin synthesis as well as its regulation. This paper is a an attempt for a concise overview concerning the localization, the organization and the regulation of the ex-pression of the genes related to bacteriocins synthesis, procession, export and immunity.

A Novel Bacteriocin-Like Substance Produced by Enterococcus faecium 3587

Secretion of a novel bacteriocin-like inhibitory substance from Enterococcus faecium 3587 is described herein for the first time. Whereas some bacteriocins receive their denomination based on the species or genus name of the producer microorganism, the newly discovered bacteriocin-like substance was named “enterocin 3587.” The growth characteristics of the producer strain, as well as the type of production and the primary characteristic of the peptide, were investigated. It was found by sodium dodecyl sulfate–polyacrylamide gel electrophoresis that the molecule possesses a molecular weight <6.5 kDa; its secretion is growth-phase dependent; and it shows activities only against other closely related enterococci but not against other Gram-positive bacteria, such as L. innocua, S. aureus 209, and Lactobacillus delbrueckii B2, nor against some Gram-negative species, such as Escherichia coli HB101.

MOLECULAR TYPING BY GENUS-SPECIFIC PCR AND RAPD PROFILING OF DIVERSE LACTOBACILLUS DELBRUECKII STRAINS ISOLATED FROM COW, SHEEP AND BUFFALO YOGHURTS

ABSTRACT A collection of twenty Lactobacillus strains isolated from yoghurts coming from different sources, and determined as Lactobacillus delbrueckii by morphological, physiological and biochemical tests (13), was subjected to PCR-based methods for typing. They were screened by two sets of Genus-specific PCR (GS-PCR) primers which confirmed their affiliation to the genus Lactobacillus. Although these dairy bacteria belong to the same species, some of them which were studied in a previous research (4) showed a few differences in their growth characteristics, probably reflecting their relatedness. In this study their phylogenic divergence was further investigated by randomly amplified polymorphic DNA (RAPD) analysis using ten different oligonucleotide primers.

BIOACTIVE PEPTIDES USED BY BACTERIA IN THE CONCUR-RENCE FOR THE ECOLOGICAL NICHE: GENERAL CLASSIFICATION AND MODE OF ACTION (OVERVIEW)

Many bacteria are producers of toxins with protein nature and relatively narrow spectra of activities against closely related species. These toxins are used in the concurrence for the occupation of the ecological re-cesses. They are showing great diversity concerning their mode of action, as well as their structure, genetic determinants and mechanisms of resistance and immunity. The best characterized for the moment are the groups of so called

Developmental and Organ-Specific Expression of Transferrin in Drosophila Melanogaster

ABSTRACT Polyclonal antibodies raised against recombinant D. melanogaster transferrin were used to study both developmental and organ-specific expression of D. melanogaster transferrin. It was shown that transferrin is present at all developmental stages except late embryos and early larvae. The organ distribution of transferrin reveals that it is abundant in the hemolymph and from all organs examined was detected only in the ovaries. The maternal origin of the transferrin in early embryos, the activation of its synthesis and its accumulation in the oocytes are discussed.

A Preliminary Characterization of a Novel Bacteriocin-Like Substance from Enterococcus Durum M-3

ABSTRACT Secretion of a novel bacteriocin-like substance from Enterococcus durum M-3 is described for the first time. The bacteriocin was named duracin. The growth characteristics of the producer strain, as well as the type of production and the primary characteristic of the peptide are investigated. It was found that the molecule has a very low molecular weight, its secretion is growth-phase dependent and it shows activities against other enterococci, Listeria innocua, Staphylococcus aureus and Lactobacillus delbrueckii B2 but not against E. coli.

pSDTV vector: a modification of the pBluescript SK+ plasmid in order to perform PCR-fragments TA-cloning using Eam1105I restriction endonuclease

Some of the approaches for cloning PCR products obtained with conventional Taq-polymerases which do not involve modifications of the ends of the vector or the insert are based on the use of restriction enzymes which can generate 3′ thymine single nucleotide overhangs, such as Eam1105I (AhdI). Due to the presence of Eam1105I restriction site within the β-lactamase gene, this is not achievable with a number of the most widely used cloning vectors descending from the pUC family, for which the selection is based on the ampicillin resistance. In this report we describe the construction of a vector for TA-cloning, based on the abolishment of the Eam1105I recognition site within the β-lactamase gene by site-directed mutagenesis, and the introduction of a stuffer flanked by Eam1105I target sites within the polylinker of the pBluescript SK+ plasmid.

Rapid identification of Enterococcus faecalis by species-specific primers based on the genes involved in the Entner–Doudoroff pathway

In this study we report a novel method for identification of Enterococcus faecalis based on polymerase chain reaction with primers specific for the eda-genes encoding the enzymes involved in the Entner–Doudoroff pathway, a pathway present only in this species among Gram-positive bacteria. The designed primers were checked in several different Enterococcus species, and with some other Gram-positive and Gram-negative bacterial species as well. Five primer combinations were used to detect the eda-1 gene, and another three for the eda-2 gene. With the exception of one of the primer combinations, all the others gave as results the expected amplification products only in E. faecalis strains.

Growth Characteristics of Twenty Lactobacillus Delbrueckii Strains Isolated from Bulgarian Home Made Yoghurts

ABSTRACT Among other microorganisms twenty Lactobacillus strains were isolated from home made yoghurts from different sources across Bulgaria. 13 strains were obtained from yoghurts prepared from cow milks while the origin of another 4 strains were sheeps milks, and 3 buffalos milk yoghurts. The strains were previously classified with API tests to belong to the species Lactobacillus delbrueckii. In this study their growth characteristics at different temperatures were obtained, and a simplified mathematical growth model was proposed.

Assessment of Cell Density and Acidifying Properties Variation of Forty-Two Lactobacillus Strains Isolated from “Lukanka” Sausage

ABSTRACT Forty-two Lactobacillus strains isolated from „Lukanka” sausage were examined on the level of growth monitored by optical density within 72 hours spread on twelve time classes. The range of the OD comprises recorded values within the range of minimum (0) and maximum (2.31). Standard deviation of the observed OD varies between. The pH level of the cultures with recorded OD600 comprises values between minimum and maximum (3.60 to 6.00) with standard deviation (0.84). We applied a linear regression models in the study for statistical analysis of the variation of the recorded traits considered with the categories of the measured fixed effects of strain and hour. The GLM estimates of the recorded ODs and the induced acidity have high significance of the variances (F-statistics, P <0.001). The differences between the averages of the categories within the strains and hours give us information about the possible variation dependences at following significance.