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Research has been conducted on Bacillus sphaericos strains. The resistance evolution to these strains in Culex quinquefaciatus populations collected from China and Brazil has been investigated and the details are reported.

Research has been conducted on Latin American Bacillus thuringiensis. The authors have characterized several strains from this bacterium, and have reported the identification of mosquitocidal cry and cyt gene carried out via the use of PCR analysis.

Both Bacillus sphaericus and Bacillus thuringiensis subsp. israelensis produce mosquitocidal toxins during sporulation and are extensively used in the field for control of mosquito populations. All the known toxins of the latter organism are known to be encoded on a large plasmid, pBtoxis. In an attempt to combine the best properties of the two bacteria, an erythromycin resistance-marked pBtoxis plasmid was transferred to B. sphaericus by a mating technique. The resulting transconjugant bacteria were significantly more toxic to Aedes aegypti mosquitoes and were able to overcome resistance to B. sphaericus in a resistant colony of Culex quinquefasciatus, apparently due to the production of Cry11A but not Cry4A or Cry4B. The stability of the plasmid in the B. sphaericus host was moderate during vegetative growth, but segregational instability was observed, which led to substantial rates of plasmid loss during sporulation. [ABSTRACT FROM AUTHOR]