species, such as B. thuringiensis subsp. jegathesan; these also
offer promise for use in new types of larvicide.
Aside from this variety of mosquitocidal proteins, several
genetic elements have been identified that, when used in
combination with strong Bt promoters, can be used to improve
efficacy by increasing endotoxin synthesis significantly. The
most important of these are the STAB/SD sequence, a ninenucleotide
polypurine sequence that improves transcript
stability and thus endotoxin synthesis, and a 20-kDa protein
that occurs naturally in the Cry11A operon. This protein
enhances net synthesis of Cry11A and other proteins and
apparently acts as a molecular chaperone.
The biochemical and toxicological differences between
mosquitocidal Bt and Bs toxins prompted several attempts
during the late 1980s and 1990s to construct recombinant
bacteria that combined the best properties of these species.
However, none of the resultant recombinants had efficacy
sufficiently improved over wild-type strains to warrant
commercial development. The prospects for developing
recombinant bacteria with high efficacy suitable for
commercial development have improved recently due to the
availability of genetic elements for improving endotoxin
synthesis, a greater range of mosquitocidal proteins and the
development of a better understanding of the toxicological
properties of Cyt1A. In this overview, we first describe the
properties of Bti and Bs and summarize previous research on
improving bacteria for mosquito control. We then go on to
show how new knowledge and technologies have been used to create recombinant bacteria that have much better potential for
use in operational mosquito control programs owing to their
very high efficacy and built-in resistant management properties
based on Cyt1A. The literature on Bt, Bti and Bs is extensive
and thus, in this overview, we cite review papers to guide
interested readers to the original literature.