Biomedical subjects

V Miteva

Publications and source records attributed to V Miteva.

16 recordsLinked to original sources

PubMed2001

Differentiation of Lactobacillus delbrueckii subspecies by ribotyping and amplified ribosomal DNA restriction analysis (ARDRA).

AIMS: To differentiate the subspecies of Lactobacillus delbrueckii, subsp. delbrueckii, subsp. lactis and subsp. bulgaricus. METHODS AND RESULTS: Amplified ribosomal DNA restriction analysis (ARDRA) and ribotyping were applied to over 30 strains. Both methods analyse the ribosomal genes which carry useful information about the evolutionary and taxonomic relationship among bacteria. The methods proved to be reliable and highly reproducible. ARDRA was applied to 16S rDNA, 23S rDNA and the IGS region, thus covering the whole rrn operon with eight restriction enzymes. Only EcoRI differentiated Lact. delbrueckii subsp. bulgaricus from Lact. delbrueckii subsp. delbrueckii/Lact. delbrueckii subsp. lactis, which confirmed the finding of other authors. Ribotyping with different enzymes under precisely optimized conditions revealed a high level of strain polymorphism. Only ribotyping with EcoRI allowed differentiation of the three subspecies on the basis of typical hybridization patterns. CONCLUSION: The successful differentiation of the three subspecies of Lact. delbrueckii by EcoRI ribotyping offers a new possibility for precise identification and differentiation of strains and new isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: Both methods could be used for differentiation of Lact. delbrueckii subspecies.

Bacterial Typing Techniques↗

PubMed1998

Characterization of a bacteriocin produced by Streptococcus thermophilus 81.

A new bacteriocin, produced by Streptococcus thermophilus 81 has been isolated, purified and characterized. By its heat sensitivity and broad inhibitory spectrum it does not resemble any other S. thermophilus bacteriocin. The mode of action is bacteriostatic. This peptide of 32 amino acids is efficient against several Bacillus species, Listeria monocytogenes, Salmonella typhimurium, Escherichia coli, Yersinia pseudotuberculosis and Yersinia enterocolitica. This bacteriocin is heat labile but its activity was not altered by pH variation from 3 to 10. Six months of storage at 40 degrees C did not influence the activity. The inactivation by detergents and the inability to resolve the protein in SDS-PAGE supposes a more complex structure or a possible stabilizing effect of other molecules. The low sensitivity of Lactobacillus delbrueckii subsp. bulgaricus to the isolated bacteriocin suggests that S. thermophilus 81 may be used in yoghurt starters.

Animals↗

PubMed1998

Characterization of bacteriocins produced by strains from traditional Bulgarian dairy products.

A result of extensive screening of over 300 strains from the Collection of ELBY Bulgaricum, PLC, thirty six strains were selected as producers of bacteriocins, active closely related lactic acid bacterial species and some food spoilage bacteria. The selected strains belong to L. helveticus, L. bulgaricus and S. thermophilus, which are rare bacteriocin producers. Nineteen nonidentified producers were characterized by molecular taxonomic approaches--M13 fingerprinting, repetitive PCR, ribotyping and hybridization with species-specific probes, which allowed to affiliate them to the species L. delbrueckii. Several strains were found to harbour plasmids of different size. The estimated activity against food borne pathogens makes the isolated substances perspective as safe food preservatives and the producing strains could be used as components of starters with improved quality.

Bacteria↗

PubMed1998

Detection and characterization of a novel antibacterial substance produced by a Lactobacillus delbrueckii strain 1043.

A novel antibacterial substance produced by a strain isolated from Bulgarian yellow cheese was characterized. The producer strain was identified by molecular typing to belong to the species Lactobacillus delbrueckii, which is a rare producer of bacteriocins. The inhibitory agent was heat stable and active against lactic acid bacteria species and several food-borne pathogens: Listeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Yersinia enterocolitica and Y. pseudotuberculosis. Its sensitivity to amylolitic enzymes and lipase suggested that a lipid and carbohydrate moiety could be important for the activity. The amino acid content of the purified bacteriocin was estimated to 29 amino acids. The bacteriocin was shown to be small (3.6-6 kDa) by three different methods: HPLC gel-filtration, SDS-PAGE and amino acid contents.

Adsorption↗

PubMed1998

Comparative genome analysis of Bacillus sphaericus by ribotyping, M13 hybridization, and M13 polymerase chain reaction fingerprinting.

A comparative genome analysis of 15 strains representing the five homology groups of the highly heterogeneous species Bacillus sphaericus was performed by M13 hybridization fingerprinting, M13 polymerase chain reaction fingerprinting, and ribotyping with the whole rrn operon. The computer cluster analyses of the polymorphic patterns, presented in dendrograms, showed that these methods allow the differentiation of the individual strains and some homology groups. Our results confirm the close genetic relatedness of the mosquito pathogenic strains of group IIA and support the idea for differentiation of a separate species. At the same time, we present additional proof of the significant genetic heterogeneity of B. sphaericus and the necessity of reconsideration of its present classification.

Bacillus↗

PubMed1992

Genomic variations in mosquitocidal strains of Bacillus sphaericus detected by M13 DNA fingerprinting.

The genomic variation of Bacillus sphaericus reference and local strains belonging to different serotypes was examined by DNA fingerprinting. A phage M13 DNA probe detected a number of variable fragments in the restriction digests of total strain DNAs. The patterns of band distribution showed a certain homology among mosquitocidal strains, expressed by similarity index D and might be a reliable criterion for assessing the level of genomic similarity between closely related strains. An important advantage of DNA fingerprinting is the differentiation of one bacterial strain from another, both expressing common phenotype and possessing highly similar genomic portions. The strain variation revealed by the M13 probe will be useful for characterization of individual strains within a serotype. It could help as well to solve some uncertain cases based on the results obtained by other methods of identification.

Animals↗

PubMed1990

[The phage sensitivity and insecticidal activity of local strains of Bacillus sphaericus].

The sensitivity of 132 local isolates of B. sphaericus to phages 3, 4 and SST of A. Yousten has been studied. According to this incomplete phage typing, most of the strains are classified in the third phage group. A high-degree correlation between sensitivity to phage 4 and insecticidal activity was established, owing to which this sensitivity can be used as an initial criterion for selection of newly isolated strains. LC50 and LC90 of one reference and six local strains of B. sphaericus were determined using Culex pipiens third instar larvae, and the local strains were found to exceed in insecticidal activity the reference strain 2362. This suggests that the newly isolated strains are promising for developing of a preparation for biological control of mosquitoes.

Animals↗

PubMed1988