Longitudinal dynamics of intestinal bacteria in the life cycle and their effects on growth and development of potato tuber moth

Potato tuber moth (PTM), Phthorimaea operculella (Lepidoptera: Gelechiidae), is an oligophagous pest that damages potatoes. Intestinal microorganisms play important roles in regulating the life activities of host insects. The gut of PTM is rich in microbials, but it is unclear that the dynamics of the structure and diversity of intestinal bacteria in the different development period of potato tuber moth. In this study, the dynamics of the intestinal bacterial community across the whole life cycle of PTM were evaluated using single molecule real-time sequencing. The intestinal microbiota of PTM is predominantly composed of Proteobacteria and Firmicutes, and it is different with the difference of development stages. Wolbachia endosymbionts were the dominant species of intestinal symbiotic bacteria in eggs and the first-instar larvae. Enterococcus mundtii was the dominant species of intestinal symbiotic bacteria in the second, third and the fourth instar larvae, as well as in both male and female pupae. Moreover, the predominant species of intestinal symbiotic bacteria in female adults is Enterobacter ludwigii, while the dominant bacterial species is Serratia rubidaea in male adults. Principal component analysis and non-metric Multi-dimensional scaling analysis confirmed the differences in intestinal symbiotic bacteria structure at different developmental stages. In addition, after reintroducing the bacteria following antibiotic treatment, it was found that the antibiotics significantly inhibited the development of the potato tuber moth, whereas the gut bacteria appeared to facilitate its growth. The findings of this study will enhance our understanding of intestinal microorganisms on the development of their host insects across the life cycle. Moreover, it will establish a foundation for elucidating the physiological functions of key microorganisms in the intestinal tract of the potato tuber moth, while also offering new insights and strategy to the biological control of this pest.

马铃薯块茎蛾（Potato tuber moth，简称PTM），即茄块茎蛾（Phthorimaea operculella，鳞翅目：麦蛾科），是一种为害马铃薯的寡食性害虫。肠道微生物在调控宿主昆虫的生命活动中发挥着重要作用。马铃薯块茎蛾的肠道中富含微生物，但目前尚不明确其肠道细菌的结构与多样性在不同发育阶段的动态变化规律。本研究采用单分子实时测序（single molecule real-time sequencing）技术，解析了马铃薯块茎蛾整个生命周期内肠道细菌群落的动态变化。结果显示，该虫肠道菌群主要由变形菌门（Proteobacteria）和厚壁菌门（Firmicutes）构成，且菌群结构随发育阶段不同而存在显著差异。沃尔巴克氏体（Wolbachia）内共生菌是卵期及1龄幼虫肠道共生菌的优势类群；蒙氏肠球菌（Enterococcus mundtii）则为2、3、4龄幼虫以及雌雄蛹期肠道共生菌的优势类群。此外，雌成虫肠道共生菌的优势类群为路德维希肠杆菌（Enterobacter ludwigii），而雄成虫肠道的优势细菌类群为深红沙雷氏菌（Serratia rubidaea）。主成分分析（Principal component analysis）与非度量多维尺度分析（non-metric Multi-dimensional scaling analysis）均证实了不同发育阶段肠道共生菌结构的差异。除此之外，在抗生素处理后重新引入肠道细菌的实验中发现，抗生素可显著抑制马铃薯块茎蛾的生长发育，而肠道细菌则可促进其生长。本研究结果有助于加深我们对肠道微生物在宿主昆虫整个生命周期中发育调控作用的理解，同时可为阐明马铃薯块茎蛾肠道关键微生物的生理功能奠定基础，也为该害虫的生物防治提供了新的思路与策略。