Efficient expression of mosquito-larvicidal proteins in a gram-negative bacterium capable of recolonization in the guts of Anopheles dirus larva

The gram-negative bacterium, An11/2 G1, isolated from the guts of Anopheles dirus mosquito larvae, was identified as Enterobacter amnigenus. The E. am nigenus was able to recolonize in the gut of An. dirus larva but not in tho se of Aedes aegypti and Culex quinquefasciatus larvae. It was able to float in water for a longer period than Bacillus thuringiensis subsp. israelensi s and Bacillus sphaericus. These are desirable characteristics for a delive ry vehicle of mosquito-larvicidal toxins for the control of mosquito larvae , and E. amnigenus was therefore used as a host to express the cryIVB gene of B. thuringiensis subsp. israelensis and the binary toxin genes of B. sph aericus. The recombinant E. amnigenus produced a high level of CryIVB prote in, which was toxic to larvae of Ae. aegypti and An. dirus. Another E. amni genus producing the 51-kDa protein of B. sphaericus was toxic to larvae of An. dirus and Cx. quinquefasciatus. The recombinant plasmids were stable in E. amnigenus without the presence of selective pressure for at least 23 ge nerations. The recombinant E. amnigenus should represent a desirable biolog ical agent for controlling mosquito larvae.