DISTRIBUTION AND CHARACTERIZATION OF MOSQUITOCIDAL TOXIN GENES IN SOME STRAINS OF BACILLUS-SPHAERICUS

The binary toxin of Bacillus sphaericus strains forms a crystal in spo rulating cells, while the mosquitocidal toxin is located in the cytopl asm of vegetative cells, The distribution of binary toxin (btx) and mo squitocidal toxin (mtx) genes in 53 strains of B. sphaericus was deter mined by hybridization of specific gene probes to chromosomal DNA in S outhern blots. btx genes were found in all strains of serotype 5a5b ex amined and in some strains of serotypes 1a, 3, 6, 25, and 48, while mt x genes were detected in strains of serotypes 1a, 2a2b, 5a5b, 6, 9a9c, 25, and 48. Serotype 26a26b strains lacked both toxin genes, as did s ome strains of serotypes 2a2b, 3, 6, and 48, Partial DNA sequences of btx genes from five strains, together with published sequences, reveal ed four types of toxin among mosquitocidal B. sphaericus strains, Most of the 42-kDa toxin gene of btx was identical in strains from serotyp es 1a, 3, 6, and 48, and the gene is here classified as a type 1 btx g ene, A serotype 3 strain isolated in Singapore possessed a unique 42-k Da toxin gene, here designated type 4; while the btx genes from strain s of serotypes 5a5b and 25 are referred to as types 2 and 3, respectiv ely.