Professional Joined: 23 Oct. 08 Location: London Online Status: Offline Posts: 2052 Posted: 05 March 09 at 03:26 Bacillus thuringiensis is a Gram-positive , soil-dwelling bacterium of the genus Bacillus . Additionally, B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies , as well as on the