两种象甲幼虫肠道微生物组成及对高单宁食物的适应

【目的】象甲是栎属植物橡子中主要的寄生昆虫,但其适应高单宁食物(橡子)的肠道微生物基础尚待揭示。本研究分析了蒙古栎和辽东栎橡子中两种柞栎象(Curculio arakawai和C.dentipes)幼虫的肠道菌群结构和多样性,试图阐明柞栎象幼虫适应高单宁食物的肠道微生物基础。【方法】分别提取蒙古栎和辽东栎橡子中象甲幼虫各50头的肠道DNA,利用Illumina MiSeq技术对肠道菌群的V3–V4区序列进行16S rRNA测序,统计样品操作分类单元(OTU)数量,分析物种组成丰度、α多样性和β多样性。【结果】结果表明,可用于物种分类的OTU分别有2054和2308个,C. arakawai和C. dentipes共有的OUT 481个。在两种柞栎象C. arakawai和C. dentipes肠道菌群中,共注释到的主要分类阶元有27个门、145个科和274个属。变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes)在两种象甲肠道菌群中占优势;假单胞菌属Pseudomonas(63.8%)、沙雷氏菌属Serratia(6%)和不动杆菌属Acinetobacter (5.2%)是C. arakawai肠道中的主要类群,而沙雷氏菌属Serratia (32%)、拉恩菌属Rahnella(24.2%)、气单胞菌属Aeromonas(6.8%)和立克次体属Rickettsia(6.6%)在C.dentipes肠道菌群中占主导优势。C. arakawai和C. dentipes肠道菌群α多样性无显著差异,β多样性则差异显著。具有单宁酶活性的肠道细菌,如粘质沙雷菌Serratia marcescens、乳球菌Lactococcus lactis、假单胞菌Pseudomonas spp.在C. arakawai和C. dentipes之间差异不显著。【结论】寄生在蒙古栎和辽东栎橡子中的C. arakawai和C.dentipes肠道菌群组成迥异,这可能与遗传因素和食物特点有关。具有单宁酶活性的粘质沙雷氏菌Serratia marcescens和乳球菌Lactococcus lactis等菌类可能是两种象甲幼虫适应高单宁食物的肠道微生物基础。

Gut bacterial composition of two Curculio species and their adaptation to high-tannin food

Objective] Curculio beetles are major parasitic insects of oak acorns, but the mechanism of their adaptation to high-tannin food (e.g., acorns) is not clear. In this study, we compared the structure and diversity of gut bacteria of the larvae of Curculio arakawai and C. dentipes infested in Mongolian oak (Quercus mongolica) and Liaodong oak (Q. liaotungensis), to elucidate the adaptive mechanisms of weevil larvae to high-tannin food. Methods] We collected gut samples of weevil larvae for DNA extraction. V3-V4 areas were sequenced using the Illumina MiSeq technology 16S rRNA sequencing. We carried out sequence statistics of Operational Taxonomic Units (OTUs), analysis of species abundance, a and b diversity. Results] There were 2054 OTUs and 2308 OTUs of the high quality sequences obtained from the guts of the 2 weevil species, in which 481 OTUs were shared. In the gut bacterial community of C. arakawai and C. dentipes, 27 phyla, 145 families and 274 genera were identified as the major taxonomic groups. At the phylum level, Proteobacteria, Bacteroidetes and Firmicutes were dominant in the guts of C. arakawai and C. dentipes. At the genus level, Pseudomonas (63.8%), Serratia (6%) and Acinetobacter (5.2%) were the main groups in the gut of C. arakawai, while Serratia (32%), Rahnella (24.2%), Aeromonas (6.8%) and Rickettsia (6.6%) were dormant in the gut of C. dentipes. Our a diversity analyses showed no significant differences between the gut bacteria of C. arakawai and C. dentipes; however, b diversity showed significant difference between the gut bacteria of C. arakawai and C. dentipes. Conclusion] Differences in gut bacterial community may be related to differences in species of weevils and host tannin content. We also found several bacteria related to the degradation of tannins, e.g., Serratia marcescens and Lactococcus lactis, which may reflect the adaptive basis for two weevil species to use high tannin food.