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P25: Biotechnological Potential and Large Plasmids of T, D. Chitavichius

Title:

Mr.

First Name:

Donaldas

Family Name:

Chitavichius

Position:

Head of Department of Microbiology

Name of organization:

Vilnius University

Address:

Chiurlionio 21/27

Postcode:

LT-2009

City:

Vilnius

Country:

Lithuania

Telephone:

+37052398205

Fax:

+37052398204

E-mail:

donaldas.citavicius@gf.vu.lt

Website:

Proposed Title

Biotechnological Potential and Large Plasmids of T

Abstract

Two directions of our scientific interests: 1. Thermophilic bacteria as the source of thermostable enzymes and proteins for food industry, pharmacology and molecular biology: Wide temperature range proteases, Bacteriocins, Isoschizomers of restriction endonucleases. 2. Large plasmids of thermophilic endospore-forming bacteria: Diversity of large plasmids of bacteria isolated from the specific environment, Structure and role of the plasmids in the cell and in the horizontal transfer of genetic information. Both of these directions are partially related, because some proteins of biotechnological potential can be encoded by plasmids. Start positions: The collection of thermophilic bacteria were isolated from a geothermal site near the Baltic Sea in Lithuania where the temperature reaches 80°C. 21 of them were analysed for the presence of plasmids. Six of them were found to harbour large covalently closed circular DNA molecules with sizes ranging between 40 and 60 kb. It is possible that one of the plasmid-bearing strains harbours two plasmids. What is the physiological significance of such large plasmids? The plasmid could play a significant role in microbial competition for nutrient sources by encoding antimicrobial substances. 20 strains of our collection have been shown to possess antimicrobial activity. We have shown that curing of the 60 kb plasmid is associated with the loss of bacteriocinogenic activity. After curing of plasmid DNA with ethidium bromide the bacteriocinogenic activity of the strain disappears. Spontaneous loss of the plasmid from strain 18 preserving it at 4°C in cultures on slants goes with the loss of bacteriocinogenic activity as well. Sometimes the loss of plasmid and bacteriocinogenic activity is going with the appearance of a small (approximately 3 kb) covalently closed circular DNA molecule. Its appearance could be associated with the homologous recombination between the large plasmid DNA and the chromosome. Thus, we propose that elimination or integration of plasmid DNA is associated with the loss of bacteriocinogenic activity. This bacteriocin is about 10 kDa in size. It was isolated from the culture supernatant of the endospore-forming bacterium belonging to the genus Geobacillus. It is the first such a small bacteriocin ever discovered in this genus. Thus, it can be concluded this bacteriocin to be the novel one. Protease from the thermophilic endospore-forming bacteria was identified. It was active in the wide temperature range – from 20 to 70 °C. The structure, relations and diversity of the plasmids can be determined by sequencing. The plasmid gene encoding bacteriocin and the gene encoding the wide temperature range protease should be cloned, the usage in food industry and pharmacology should be analysed.

A. Enterprises Corner

Enterprises looking for complementary partners in research arena and

Researchers offer their findings for technology transfer to enterprises

B. Research Corner

x

Research institutions looking for partners for joint research venture

x

Potentially interested for continuation of projects preparations on Tuesday afternoon 1 st July

Keywords

thermophilic, plasmids, bacteriocin, protease, structure

Received: 17/6/2003

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