The present invention relates to novel bacteria strains that can be used in biological control against mosquito larvae (Culex spp.). The protein obtained from a novel B. sphaericus spp. isolates with the invention is used as larvicide, the step of isolating the protein at product obtaining stage is eliminated. By means of the invention, thee bacterial strains (MIB 5,6,7) investigated for biological control of mosquitoes are effective in both polluted and fresh water.