Current Trends in Natural Sciences, Pitesti, Romania, 18 - 20 April 2019, pp.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.