Gut bacterial community structure shifts in successive generations of Spodoptera exigua under short-term thermal stress

<p class="MsoNormal"><span>Long-term studies that advance our mechanistic understanding of gut bacterial symbionts of insect hosts in response to the successive generations of short-term thermal stress are lacking. The beet armyworm, <em>Spodoptera exigua</em> </span><span>is a notorious agricultural pest worldwide</span><span> and has often experienced stressful temperature fluctuations in field environments. In this study, 1,795,224 reads and 2,565 operational taxonomic units (OTUs) were detected in 23 gut samples of<em> S. exigua</em> fed for five successive generations<em> </em>using 16S rRNA high-throughput sequencing technology. Overall, we identified 618 bacterial genera from 30 phyla, and Proteobacteria and Firmicutes were the most dominant phyla. <a name="_Hlk98529962"></a><a name="_Hlk98688137"></a><span>Alpha-diversity </span><span>of gut microbiome revealed significant differences among these generation </span>treatment groups<em>.</em> We detected the highest bacterial richness and alpha diversity in the fifth generation and the lowest in the first generation under short-term thermal stress.<a name="_Hlk98529975"></a> Beta diversity indicated that the gut microbial community structure of <em>S. exigua</em> in the first generation was significantly different from that of other generations. Finally,<a name="_Hlk98576503"></a> </span><span><span>PICRUSt </span></span><span><span>analysis showed that </span></span><span>most functional prediction categories</span><span> were </span><span>related to</span><span> RNA processing and modification</span><span>.</span><span> Our findings represent the first investigation of the successive generations of short-term thermal stress that can affect the microbial communities associated with lepidopteran insects and broaden our understanding of the ecological adaptation of this species.</span></p>