Li Yazi, Zhao Dan, Wu Han, Ji Yujie, Liu Zhaorui, Guo Xiaochang, Guo Wei, Bi Yang
College of Plant Protection, Hebei Agricultural University, Baoding, China.
Graduate School of Chinese Academy of Agricultural Sciences, Beijing, China.
Front Microbiol. 2022 Mar 23;13:835227. doi: 10.3389/fmicb.2022.835227. eCollection 2022.
The Beet armyworm (Lepidoptera: Noctuidae, Spodoptera) is an important global polyphagous pest. Pathogen infection could destroy the intestinal microbial homeostasis of insects, leading to the death of the host. However, the effect of the host intestinal microbial community on the insecticidal effect of is rarely studied. In this study, the genome characteristics of Bt GS57 and the diversity and functions of the gut bacteria in are investigated using crystal morphology, biological activity, and Illumina HiSeq high-throughput sequencing. The total size of the Bt GS57 genome is 6.17 Mbp with an average G + C content of 35.66%. Furthermore, the Bt GS57 genome contains six genes: , , , , , and , and a vegetative insecticidal protein gene . The Bt GS57 strain can produce biconical crystals, mainly expressing 70 kDa and 130 kDa crystal proteins. The LC value of the Bt GS57 strain against the larvae was 0.339 mg mL. Physiological and biochemical reactions showed that Bt GS57 belongs to var. . In addition, we found that can cause a dynamic change in the gut microbiota of , with a significant reduction in bacterial diversity and a substantial increase in bacterial load. In turn, loss of gut microbiota significantly decreased the susceptibility of larvae. Our findings reveal the vital contribution of the gut microbiota in -killing activity, providing new insights into the mechanisms of pathogenesis in insects.
甜菜夜蛾（鳞翅目：夜蛾科，Spodoptera属）是一种重要的全球多食性害虫。病原体感染会破坏昆虫肠道微生物的稳态，导致宿主死亡。然而，宿主肠道微生物群落对苏云金芽孢杆菌（Bt）杀虫效果的影响鲜有研究。在本研究中，利用晶体形态、生物活性和Illumina HiSeq高通量测序技术，研究了Bt GS57的基因组特征以及甜菜夜蛾肠道细菌的多样性和功能。Bt GS57基因组的总大小为6.17 Mbp，平均G + C含量为35.66%。此外，Bt GS57基因组包含六个cry基因：cry1Aa、cry1Ab、cry1Ac、cry1Ca、cry2Aa和cry2Ab，以及一个营养期杀虫蛋白基因vip3Aa。Bt GS57菌株可产生双锥形晶体，主要表达70 kDa和130 kDa的晶体蛋白。Bt GS57菌株对甜菜夜蛾幼虫的LC50值为0.339 mg/mL。生理生化反应表明，Bt GS57属于库斯塔克变种（kurstaki）。此外，我们发现Bt可导致甜菜夜蛾肠道微生物群发生动态变化，细菌多样性显著降低，细菌载量大幅增加。反过来，肠道微生物群的丧失显著降低了甜菜夜蛾幼虫对Bt的敏感性。我们的研究结果揭示了肠道微生物群在Bt杀虫活性中的重要作用，为昆虫中Bt致病机制提供了新的见解。
