The genome history of Bacillus thuringiensis subsp. tenebrionis: From discovery to present day product

Bacillus thuringiensis subsp. tenebrionis (Btt) was discovered in 1982 and has been used as a biological control agent against the Colorado potato beetle (Leptinotarsa decemlineata) since the early 1990s. In this study, we sequenced, assembled and analysed the genome of strain DSM 2803, which is the patent deposit of the original Btt isolate BI 256-82. A high-quality reference genome is provided that allows investigating the genomic changes throughout the commercial history of Btt. Strain DSM 2803 (BI 256-82) is particularly interesting since the subspecies description of ‘tenebrionis’ is based on it and because it represents the genomic origin of the commercial Btt strain currently used in plant protection. Comparative genome analysis of six Btt strains derived from BI 256-82 revealed that the genomes were generally highly similar. However, some plasticity in the profile of extrachromosomal elements was detected, including recombination-dependent plasmid differences and the presence/absence of a circular plasmid-like prophage.