Departamento de Biotecnologia, Universidade Federal de Tocantins, Gurupi, TO, 77413-070, Brazil.
Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, 70910-900, Brazil.
Sci Rep. 2020 Mar 26;10(1):5518. doi: 10.1038/s41598-020-60670-7.
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 = 0.015 µg/ml) and C. quinquefasciatus larvae (LC = 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.
苏云金芽孢杆菌以色列亚种（Bti）被用于控制人类和动物疾病的昆虫病媒。在本研究中，分析了 4 株苏云金芽孢杆菌菌株（T0124、T0131、T0137 和 T0139）对埃及伊蚊和致倦库蚊幼虫的毒性。与其他菌株相比，T0131 菌株对埃及伊蚊幼虫（LC=0.015µg/ml）和致倦库蚊幼虫（LC=0.035µg/ml）的杀虫活性最高。此外，还获得了这 4 株菌株的基因组序列并进行了比较。这些 Bti 菌株的染色体大小约为 5.4Mb，GC 含量约为 35%，有 5472-5477 个潜在的编码区。在所有 4 株菌株的染色体外内容物中发现了 3 个小质粒（5.4、6.8 和 7.6kb）和 3 个大质粒（127、235 和 359kb）。基于 SNP 的系统发育树显示，本研究中的分离株与其他 Bti 分离株之间存在密切关系，而 127kb 质粒的 SNP 分析并未显示δ-内毒素基因发生任何突变。这些新获得的 Bti 菌株的序列数据可能有助于寻找新的杀虫毒素，以改进现有毒素或开发针对人类和动物疾病重要昆虫病媒的新生物防治策略。
