Recombinant Enterobacter amnigenus highly toxic to Anopheles dirus mosquito larvae

The mosquito-larvicidal binary toxin of Bacillus sphaericus 2297 was expres sed in Enterobacter amnigenus, a Gram-negative bacterium isolated from Anop heles dirus larvae gut. The toxin was placed under the regulation of variou s promoters in order to improve the expression level of the toxin. Amongst the recombinants obtained, E. amnigenus harboring pBS373, a plasmid which c ontains the toxin genes under the control of the native B. sphaericus promo ter, expressed a significant amount of protein, comparable to that found in B. sphaericus 2297. In addition, this recombinant provided approximately t wenty times higher toxicity against second-instar Anopheles dirus larvae wh en compared to B. sphaericus 2297. The procedure of obtaining this environm entally isolated bacterium from larvae gut and introducing the system for m osquito-larvicidal toxin synthesis is noteworthy. The promising result pres ented here provides a substantial degree of confidence for further field st udies.