Recent discovery of endophytic strains of Bacillus thuringiensis significantly improves the knowledge on its ecology. It also may be a new source for the isolation of insecticidal strains. This report shows the characterization of two endophytic, highly insecticidal strains of B. thuringiensis. Strains LBIT-1250L and LBIT-1251P were isolated from lavender and Poinsettia sap, respectively. Their parasporal crystals were very similar in morphology to those shown by serotypes israelensis and kurstaki, respectively. Bioassays on Aedes aegypti fourth instar larvae and on Manduca sexta first instar larvae, respectively, showed significantly higher levels of toxicity than those of their standard counterparts, IPS-82 (israelensis) and HD-1 (kurstaki) strains, respectively. Characterization of both strains included the sequencing of flagellin (hag) gene, plasmid and Bc Rep-PCR patterns and crystal protein content. All four characterization features indicated that LBIT1250L is highly related to the IPS-82 standard (serotype H-14: israelensis); while the LBIT-1251P was highly related to the HD-1 standard (serotype H-3a3b3c kurstaki). These results indicate that endophytic strains of B. thuringiensis may be a new source of potential insecticidal strains and opens more in-depth studies about the role of this bacterium in such a specialized habitat.

中文翻译：

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苏云金芽孢杆菌两种高效杀虫内生菌株的分离和鉴定

最近苏云金芽孢杆菌内生菌株的发现显着提高了对其生态学的认识。它也可能成为分离杀虫菌株的新来源。该报告展示了苏云金芽孢杆菌的两种内生、高杀虫力菌株的特征。菌株 LBIT-1250L 和 LBIT-1251P 分别从薰衣草和一品红的汁液中分离出来。它们的伴孢晶体在形态上分别与israelensis和kurstaki血清型非常相似。分别对埃及伊蚊第四龄幼虫和天蛾一龄幼虫进行的生物测定显示，其毒性水平分别显着高于其标准对应品系 IPS-82（以色列）和 HD-1（库斯塔基）菌株。两种菌株的表征包括鞭毛蛋白 ( hag ) 基因的测序、质粒和 Bc Rep-PCR 模式以及晶体蛋白含量。所有四个表征特征均表明 LBIT1250L 与 IPS-82 标准（血清型 H-14： israelensis）高度相关；而LBIT-1251P与HD-1标准（血清型H-3a3b3c kurstaki ）高度相关。这些结果表明，苏云金芽孢杆菌的内生菌株可能是潜在杀虫菌株的新来源，并为该细菌在这种特殊栖息地中的作用开启了更深入的研究。