Refined, circular restriction map of the Bacillus thuringiensis subsp israelensis plasmid carrying the mosquito larvicidal genes

All the genetic elements responsible for the mosquito larval toxicity of Ba cillus thuringiensis subsp. israelensis are located on one of its largest p lasmids, nicknamed pBtoxis. Two linkage groups (with sizes of about 75 and 55 kb) have previously been mapped partially with respect to SacI and BamHI restriction sites (Ben-Dov et at, 1996), but linking them to a single circ ular plasmid unambiguously was impossible with the available data. To final ize the plasmid map, another rare cutting restriction endonuclease, AlwNI, was used in addition. The two linkage groups and the Fragments generated by AlwNI were aligned on the circular plasmid, and known insertion sequences were localized on the refined map. Pulsed-field electrophoresis revealed th at the total size of pBtoxis (137 kb) was larger than thought before. (C) 1 999 Academic Press.