Isolation and genetic characterization of Lysinibacillus sphaericus strains found in mosquito larvae (Diptera: Culicidae)

摘要

Introduction: Lysinibacillus sphaericus is a highly effective and specific bioinsecticide used for the control of Culicidae larvae. Objective: This study aimed to identify and characterize L . sphaericus strains isolated from Culex quinquefasciatus larvae in Brazil. Methods: C . quinquefasciatus larvae were collected from streams in the urban area of S?o Paulo state. L . sphaericus strains were identified through cytomorphology, biochemical, and physiological analyses. Qualitative bioassays were performed to evaluate the toxicity of the strains against C . quinquefasciatus . The crystal compound protein pattern of L . sphaericus strains was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Five reference strains were used as standards in all tests performed. Repetitive extragenic palindromic elements-polymerase chain reaction (REP-PCR) was utilized in an attempt to differentiate pathogenic and nonpathogenic isolates. Results: Twenty-one strains were isolated. Only one presented toxic activity against C . quinquefasciatus . REP-PCR results identified 23 patterns among the 26 strains used in the study, and the fragment analysis showed low similarity (16%) between L . sphaericus isolates and the five reference strains. Conclusion: Comparison of strains isolated in this study using REP-PCR showed a low similarity to other strains, demonstrating the high intraspecific variability for L . sphaericus .