An investigation on the diversity of mosquitocidal bacteria and its relationship with incidence of vector borne diseases

Control of mosquitoes is the most important aspect of public health, as mosquitoes transmit many human diseases, including the fatal infection, Japanese encephalitis. This paper addresses the isolation of new mosquitocidal bacteria from soil samples in the Union Territory of Pondicherry, India, where, no clinical cases of vector borne infections have been reported. Bacterial isolates from soil samples were screened for potential mosquitocidal strains and bioassays against mosquito vectors (Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti) were carried out. Genomic DNA of potential mosquitocidal isolates was amplified and species identification was carried out using BLASTn program (NCBI). Phylogenetic analysis of 16S rRNA sequences of mosquitocidal bacteria revealed seven potential isolates. SDS-PAGE results have shown that there was considerable difference in the protein profiles. Numerical analysis revealed 4 distinct groups at similarity level 25%. The relationship between VBDs and prevalence of soil mosquitocidal bacteria in the study sites has elicited considerable interest in the diversity of mosquitocidal bacteria and their application for mosquito borne diseases control.

Isolation of mosquitocidal bacteria (Bacillus thuringiensis, B.sphaericus and B.cereus) from excreta of arid birds.

Mosquitocidal bacteria are environmentally friendly alternatives to chemical insecticides for controlling mosquitoes and therefore, there have been tremendous world-wide efforts to identify novel mosquitocidal bacteria from natural environment. In the present study, excreta from arid-birds were analyzed for identifying mosquitocidal bacteria. The selection of sample for bacterial screening is significant, because, arid-birds are the unique living species and gathering the foods from variety of sources from environment. Out of 1000 samples examined, twelve bacterial strains were identified as mosquitocidal and the 16S rRNA gene sequence alignment depicted that these isolates belonged to Bacillus species (Bacillus thuringiensis, B.sphaericus and B.cereus). Toxicity assay against mosquito vectors have shown that these isolates are potential. The B. sphaericus VCRC-B547 (NCBI: JN377789) has shown a higher toxicity against Cx. quinquefasciatus, An. stephensi, and Aed. aegypti. Result from SDS-PAGE has shown that there was considerable difference in the protein profiles among the new bacterial isolates. Phylogenetic tree with branch length 0.05 revealed three distinct groups with homology among the closely related Bacillus strains. This study therefore throws considerable interest on the diversity of microbial organisms from arid birds and its application in mosquito control.