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 16S rRNA 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 ~ 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.