Comparative genomic analysis and mosquito larvicidal activity of four Bacillus thuringiensis serovar israelensis strains

Abstract

Bacillus thuringiensis serovar israelensis (Bti) is used to control insect vectors of human and animal diseases. in the present study, the toxicity of four strains of Bti, named T0124, T0131, T0137, and T0139, toward Aedes aegypti and Culex quinquefasciatus larvae was analyzed. The T0131 strain showed the highest larvicidal activity against A. aegypti (Lc 50 = 0.015 µg/ml) and C. quinquefasciatus larvae (Lc 50 = 0.035 µg/ml) when compared to the other strains. Furthermore, the genomic sequences of the four strains were obtained and compared. These Bti strains had chromosomes sizes of approximately 5.4 Mb with GC contents of ~35% and 5472-5477 putative coding regions. Three small plasmids (5.4, 6.8, and 7.6 kb) and three large plasmids (127, 235, and 359 kb) were found in the extrachromosomal content of all four strains. the Snp-based phylogeny revealed close relationship among isolates from this study and other Bti isolates, and SNPs analysis of the plasmids 127 kb did not reveal any mutations in δ-endotoxins genes. This newly acquired sequence data for these Bti strains may be useful in the search for novel insecticidal toxins to improve existing ones or develop new strategies for the biological control of important insect vectors of human and animal diseases.

The Distribution of Several Genomic Virulence Determinants Does Not Corroborate the Established Serotyping Classification of Bacillus thuringiensis

“…Although most of these determinants are detectable at the genomic level, proteomic assays may provide essential evidence for their distribution. To date, both genomic and proteomic techniques are utilized in Bt studies, although the number of comparative proteomics papers [10,11] is considerably smaller than that of works on comparative genomics [12][13][14][15]. Ideally, the genomic and proteomic approaches should be used in parallel in order to detect virulence factors that are either missing in the proteome screening [16] or misannotated in the genomic data [17].…”

Isolation, Genomic, and Proteomic Characterization of a Novel Neotropical Strain of Bacillus thuringiensis with Mosquitocidal Activities

“…Despite the characterization of genes coding pesticidal proteins allowing strain classification, it is the expression of these genes that determines their spectrum of activity [18,19]. In the genome sequence, not all annotated coding regions are expressed, and the genomic approach may not suffice to fully explain the toxicity differences between Bt strains [20,21]. For instance, many pesticidal proteins are cryptic or have insignificant levels of expression [22].…”

“…Several studies have been conducted to investigate the genomics of mosquitocidal Bt strains [21,[27][28][29]. Interestingly, the proteomic analysis for pesticidal proteins responsible for mosquitocidal activities in Bt strains remains scarce and underexploited.…”