RELEASE OF BACILLUS-THURINGIENSIS SUBSP ISRAELENSIS IN SWEDISH SOIL

A streptomycin-resistant strain of Bacillus thuringiensis subsp. israe lensis (BtN14) was released in a field experiment and the effect on th e indigenous bacterial flora was analyzed. A minor, transient increase of the concentration of B. thuringiensis/cereus-like bacteria was det ected. The released strain was able to establish itself al a low numbe r, but the total concentration of B. thuringiensis subsp. israelensis was not affected. BtN14 was detected outside the release site, but dec reased to a concentration below the detection limit (20 cfu g(-1) soil ) at the end of the test period. Laboratory experiments showed that th e released strain can grow in non-sterilized as well as sterilized soi l, but that growth was very slow and transient in non-sterilized soil. Seven weeks after release, no remaining effects on the total bacteria l population could be detected.