Gut Microbial Communities in Mealworms and Indianmeal Moth Larvae Respond Differently to Plastic Degradation

Recent studies describe the role of specific isolated members of insect larval gut microbiota in plastic degradation. However, the effect of plastics on the entire gut microbial community composition and structure is yet unknown. To determine these roles, we studied two insect larvae - Tenebrio molitor degrades polystyrene (PS) and Plodia interpunctella degrades polyethylene (PE). We established two colonies of each species - control (fed oats) and test (fed either PS or PE). After dissecting the larvae to obtain their guts, we extracted, sequenced, and analyzed 16srRNA through amplicon sequencing. In Plodia interpunctella fed only PE, we find significant increased relative abundance of microbial families Pseudomonaceae, Clostridiaceae and Caulobacteraceae - from 0.15% in the control to about 50% in the PE-fed group. In Tenebrio molitor fed only PS, degradation is not associated with significant changes in microbial abundance. We hypothesize that Tenebrio microbiome uses other mechanisms such as protein production and/or cross feeding, retaining the original gut microbial structure and composition during PS degradation. This study showcases the diverse mechanisms used by larval gut microbiota to achieve polyethylene and polystyrene degradation, indicating a variation in the effect of plastic degradation on the gut microbial community of larvae.

现有研究已证实，昆虫幼虫肠道菌群的单一分离菌株在塑料降解过程中发挥特定作用。然而，塑料对幼虫肠道微生物群落整体组成与结构的影响仍未明确。为明确此类作用，本研究选取两种具备塑料降解能力的昆虫幼虫：可降解聚苯乙烯（polystyrene, PS）的黄粉虫（Tenebrio molitor），以及可降解聚乙烯（polyethylene, PE）的印度谷螟（Plodia interpunctella）作为研究对象。我们为每个物种建立两个实验群体：对照组饲喂燕麦，实验组则分别饲喂聚苯乙烯或聚乙烯。解剖幼虫获取肠道组织后，我们通过扩增子测序技术对16S核糖体RNA（16srRNA）进行提取、测序与分析。在仅饲喂聚乙烯的印度谷螟中，我们观察到假单胞菌科（Pseudomonaceae）、梭菌科（Clostridiaceae）与柄杆菌科（Caulobacteraceae）的相对丰度显著升高：从对照组的0.15%提升至饲喂聚乙烯组的约50%。在仅饲喂聚苯乙烯的黄粉虫中，其降解过程未伴随微生物丰度的显著变化。我们推测，黄粉虫肠道微生物组可通过蛋白质合成及/或交叉营养等其他机制，在聚苯乙烯降解过程中维持肠道原有的微生物群落结构与组成。本研究揭示了幼虫肠道菌群降解聚乙烯与聚苯乙烯所采用的多样化机制，表明塑料降解对幼虫肠道微生物群落的影响存在物种间差异。