Bacillus thuringiensis: an impotent pathogen?

Bacillus thuringiensis (Bt) is an insecticidal bacterium that has successfully been used as a biopesticide for many years. It is usually referred to as a soil-dwelling organism, as a result of the prevalence of its spores in this environment, but one that can act as an opportunistic pathogen under appropriate conditions. Our understanding of the biology of this organism has been challenged further by the recent publication of two reports that claim that Bt requires the co-operation of commensal bacteria within the gut of a susceptible insect for its virulence. It is our opinion that Bt is not primarily a saprophyte and does not require the assistance of commensal bacteria but is a true pathogen in its own right and furthermore that its primary means of reproduction is in an insect cadaver.