黑水虻幼虫中肠区块化免疫表达促进特征肠道微生物群落形成

Compartmentalized immune expression along the Hermetia illucens midgut forms characteristic gut microbiota

黑水虻Hermetia illucens L.幼虫肠道中的免疫系统既需要消灭病原体,又要创造有益环境,保留共生微生物。Toll和免疫缺陷(Immune deficiency,Imd)通路是昆虫肠道内抵御病原体的基本免疫防御机制,然而黑水虻幼虫肠道中耐受共生菌的机制尚不清楚。本研究通过对比不同废弃物(餐厨垃圾、豆渣和鸡粪)中黑水虻幼虫中肠微生物组,发现放线菌门Actinobacteria、厚壁菌门Firmicutes、拟杆菌门Bacteroidetes和变形菌门Proteobacteria在肠道中占主导,并且肠道能富集放线菌门和拟杆菌门。通过随机森林模型预测,异单胞菌Dysgonomonas、摩氏摩根菌属Morganella、厌氧球菌属Anaerococcus最有可能是中肠中的特征菌属,这些菌的存在可能对黑水虻的生长有着重要影响并且可以作为判定样品是否属于黑水虻的标准。进一步研究表明后中肠的微生物负荷平均是前中肠和中中肠的8.56倍,同时异单胞菌主要在后中肠富集。另外,前中肠和中中肠的抗菌肽表达分别是后中肠的1645倍和10.20倍,而负反馈因子在后中肠的表达平均提高了4.66倍。本研究初步表明黑水虻幼虫肠道可能对微生物具有重塑作用,幼虫在前中肠通过抗菌肽筛选微生物,并在后中肠抑制抗菌肽释放保存共生菌。综上,本研究揭示了黑水虻幼虫肠道免疫的区域化表达可维持抗病原体能力的同时为共生微生物群构建保护区域的“先清除-后招募”机制。

The immune system in the black soldier fly larva(Hermetia illucens L.,BSFL)gut must eliminate pathogens while tolerating the presence of symbiotic microbiota.The Tol and Imd pathway is an essential defense against invading pathogens in insect guts,but tolerance mechanisms are less understood.This study compared the BSFL midgut microbiota in different types of waste(food waste,bean dregs,and chicken manure)and found that Actinobacteria,Firmicutes,Bacteroidetes,and Proteobacteria were dominant in the midgut,and midgut could enrich Actinobacteria and Bacteroidetes.According to the random forest model prediction,the Dysgonomonas,Morganella,and Anaerococcus were most likely to be the characteristic genus in the midgut.Further research had shown that the microbial load in the posterior midgut was 4.52~12.6 times higher than that in the anterior and middle midgut,and that Pseudomonas aeruginosa was mainly enriched in the posterior midgut.In addition,the expression of antimicrobial peptides in the anterior and middle midgut was 1645 times and 10.2 times higher than that in the posterior midgut,respectively,while the expression of negative feedback factors increased by 4.28~5.04 times in the posterior midgut.This study demonstrated that BSFL midgut had a reconstruction effect on microorganisms.The larvae screen microorganisms through antimicrobial peptides in the anterior midgut and inhibit the release of antimicrobial peptides in the posterior midgut to preserve symbiotic bacteria.Our study describes a‘elimination-then-recruitment’mechanism by which regional expression of immune system in midgut maintains their ability to resist pathogens while constructing protective zones for the symbiotic microbiota.