Toxicity of Lysinibacillus sphaericus Q001 S-Layer Protein Against Culex quinquefasciatus and Anopheles stephensi Larvae
Toxicity of Lysinibacillus sphaericus Q001 S-Layer Protein Against Culex quinquefasciatus and Anopheles stephensi Larvae
Hamayun Arshad1, Muhammad Waris2,3 and Qurratulann Afza Gardner1*
ABSTRACT
Use of larvicidal proteins based on bacteria is regarded as an effective and environment friendly method of insect control. In this regard, surface layer (S-layer) protein in various strains of Lysinibacillus sphaericus is reported to exhibit bioinsecticidal property. Here, we aimed to search for local strain of L. sphaericus and test its S-layer protein for toxicity against Culex quinquefasciatus and Anopheles stephensi larvae. For this purpose, we isolated various bacterial strains from our local environment using standard microbiological techniques. Among those isolates, we found novel strain of L. sphaericus Q001, identified by ribotyping and MALDI-biotyping. The 16S ribosomal RNA gene of this strain is 96% similar to that of highly entomotoxic WHO reference strain 2362. The gene sequence was submitted to Genbank (OQ701385). We isolated the S-layer protein of this strain by treating it with lithium chloride (LiCl). After SDS-PAGE analysis, the protein was subjected to in-gel digestion and peptide mass fingerprinting for identification. Following the successful identification of this protein, we used it to test its toxicity against mosquito larvae by following WHO guidelines with slight modification. The bioassays were performed in triplicate and LC50 was calculated by applying log probit analysis. In conclusion, we found that S-layer protein of L. sphaericus Q001 was effective against the tested larvae with LC50 values of 8.5 µg/ml and 16.1 µg/ml against Cx. quinquefasciatus and An. stephensi larvae respectively. Furthermore, field trials can reveal the true potential of this protein as bioinsecticide.
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