Biological control alone or as a part of integrated vector management stands to be a better alternative to the chemical controls aimed against pest mosquitoes.  Here, A screening for microorganisms that can be utilized as new host cells for mosquito larvicides was carried out. As persistence in the environment is required of host cells, the bacterial populations in mosquitoes collected from natural breeding ponds around Mansoura University was examined. Bacterial sequences were isolated using standard 16S rRNA gene sequencing.  Bacillus species, especially Lysinibacillus sphaericus were found to be the dominant species andtoxic to Culex larvae, Bacillus amyloliquefaciens was the second highly effect against culex larvae, B. amyloliquefaciens was isolated from Culex larvae for the first time in Egypt. Cellulosimicrobium cellulans also isolated and had the lowest effect. Detection and isolation of these bacteria offer a potential biocontrol mechanism as they possess high potential as novel host cells for application in mosquito control.