Current Trends in Natural Sciences, Pitesti, Romanya, 18 - 20 Nisan 2019, ss.29
Bacillus thuringiensis (Bt) is a Gram (+) sporogenic
bacterium used as the most effective agent in biological control of insect
pests due to production of parasporal crystal proteins during sporulation
phase. Bt metabolites have also wide range of applications
especially in agriculture and health. Bt strains attract attention in
many other areas such as development of new antimicrobial agents against
bacterial pathogens that develop antibiotic resistance, development of
antifungal agents against pathogen fungi and development of natural food
preservatives. They also produce metabolites like siderophores, deaminases and
phosphatases, which promote growth of many plant species and provide
significant yield increases. Genes encoding these metabolites are mostly
encoded on plasmids, which are genetic materials that can replicate independent
of chromosomes in cells. The plasmids themselves and the specific information
they encode are of not vital importance for the host bacteria, however, when
expressed they confer advantage through special characters such as toxin
formation, pilus formation, virulence properties, root nodulation, plant tumor
induction, fermentation property, nitrogen and CO2 fixation, resistance to
antibiotics, heavy metals and drugs. Although there is no apparent
standardization, plasmids are classified as small (1-10kb), medium (10-40 kb)
and large (> 40 kb) according to their size. Bt strains can have 1-17 plasmids in various sizes. Plasmid genomes
are very diverse, yet, the rules governing the plasmid genomes are not fully
understood. Considering all these, plasmids are one of the key elements in
biotechnological developments in terms of DNA delivery and exogenous expression,
microbial metabolite production and genetic manipulations on them. Therefore, plasmid
genome sequencing and mapping in bacteria has great importance for the
detection and utilization of those characteristics and related regulatory
factors.