bacterial toxins (Bacillus sphaericus and B.
thuringiensis serovar israelensis): Mode of
action, cytopathological effects and mechanism of
Subbiah Poopathi* and S. Abidha
Unit of Microbiology and Immunology, Vector Control Research
Centre (Indian Council of Medical Research), Medical
complex, Indira Nagar, Puducherry – 60 5006, India.
*Corresponding author. E-mail:
Tel: 91-9443957479. Fax: 91-413-2272041.
Accepted 4 September, 2010
Neide (Bs) and
Bacillus thuringiensis serovar
israelensis deBarjac (Bti) provide
effective alternatives to broad spectrum larvicides in many
situations with little or no environmental impact. Taking
into account environmental benefits including safety for
humans and other non-target organisms, reduction of
pesticide residues in the aquatic environment, increased
activity of most other natural enemies and increased
biodiversity in aquatic ecosystems, their advantages are
numerous. In addition to recombinant bacteria used as
larvicides, research is also underway to develop transgenic
algae and cyanobacteria using larvicidal endotoxins of Bti
and Bs. The advent of recombinant DNA technology is
now having an enormous impact on agriculture and
medicine and it is appropriate that the ability
to manipulate and recombine genes with this technology
be applied to improving larvicides for vector control.
These new recombinant bacteria are as potent as many
synthetic chemical insecticides yet are much less
prone to resistance, as they typically contain a
mixture of endotoxins with different modes of action. The
existing recombinants also have what can be considered
disadvantageous in that they do not show
significantly improved activity against aedine
and anopheline mosquitoes in comparison to Bti. But
it may be possible to overcome this limitation
using some of the newly discovered mosquitocidal
proteins such as the Mtx proteins and peptides such as the
trypsin-modulating oostatic factor which could be
easily engineered for high expression in
recombinant bacteria. While other microbial
technologies such as recombinant algae and other bacteria
are being evaluated, it has yet to be shown that
these are as efficacious and environmentally
friendly as Bti and Bs. By combining the genes
from a variety of organisms, it should ultimately
be possible to design `smart' bacteria that will
seek out and kill larvae of specific vector mosquitoes.
Thus, recombinant bacteria show excellent promise
for development and use in operational vector control
programs, hopefully within the next few years.
Key words: Bacillus sphaericus, Bacillus thuringiensis
serovar israelensis, bacterial toxins, Culex
quinquefasciatus, Anopheles stephensi,
Aedes aegypti, mode of action, resistance,
management of resistance.