Research on gut microbiota of phytophagous insects has shown to be important for the physiological functions of insect hosts; however, little is known about the changes in gut microbiota when they are suffering from environmental stress or pathogen infections. During rearing of Phasmotaenia lanyuhensis (Phasmatodea: Phasmatidae), sluggish locomotion was usually followed by the death of the insect with a symptom of melanization in the front part of the abdomen. Therefore, the abnormal individuals were initially classified into moribund, light‐ and serious‐symptom based on the level of abnormal physiological circumstances and melanization. The gut microbiota of these samples were further investigated by 16S metagenomic sequencing and the differences in bacterial abundance and structure of bacterial community were analyzed. A decrease in microbiota diversity was observed in the diseased P. lanyuhensis, with the abundance of phyla Proteobacteria and Firmicute relatively higher compared to those without symptom. Interestingly, principal component analysis based on the bacterial richness was correlated to the level of melanization symptom in the diseased P. lanyuhensis, suggested the change in bacterial microbiota involved in this abnormal circumstance. However, the factor that caused the initial alternation of microbiota remains to be identified. Additionally, the lack of bacterial diversity (i.e., absence of Meiothermus and Nubsella spp.) in P. lanyuhensis might reduce the fitness for surviving. This report provided the comprehensive microbiota analysis for P. lanyuhensis and concluded that either the relative abundance or the bacterial diversity of microbiota in the insect digestive system may influence the physiological functions of phytophagous insects.

中文翻译：

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健康和患病手杖肠道菌群的比较

研究表明，对噬菌性昆虫肠道微生物群的研究对于昆虫宿主的生理功能具有重要意义。然而，当肠道菌群遭受环境压力或病原体感染时，对它们的变化知之甚少。兰竹菌的饲养过程中（Phasmatodea：Phasmatidae），运动缓慢通常是昆虫死亡，腹部前部有黑色素化症状。因此，根据异常生理状况和黑色素的水平，将异常个体最初分为垂死，轻度和严重症状。通过16S宏基因组测序进一步研究这些样品的肠道菌群，并分析细菌丰度和细菌群落结构的差异。在患病的P. lanyuhensis中观察到微生物区系的减少，有丰富的菌群变形杆菌和Firmicute。相较于无症状者 有趣的是，基于细菌丰富度的主成分分析与患病的P. lanyuhensis的黑色素化症状水平相关，表明与这种异常情况有关的细菌微生物群发生了变化。但是，引起微生物群最初轮换的因素仍有待确定。此外，兰屿疟原虫缺乏细菌多样性（即，没有嗜热菌和纳布氏菌）可能会降低其生存能力。该报告提供了对P. lanyuhensis的综合菌群分析 并得出结论，昆虫消化系统中微生物群落的相对丰度或细菌多样性可能会影响植食性昆虫的生理功能。