Superworm (Zophobas morio) gut microbiome metagenomics

Plastics are inexpensive and widely used organic polymers, but their high durability hinders biodegradation. Polystyrene, including extruded polystyrene also known as styrofoam, is among the most commonly produced plastics worldwide and is recalcitrant to microbial degradation. In this study, we examined superworms (Zophobas morio) reared on bran, polystyrene, and under starvation conditions and assessed changes in the insects gut microbiome. Superworms on a polystyrene diet achieved only minimal weight gains, but were able to complete their life cycle to pupae and imago. Microbial gut communities differed considerably between diet groups, with polystyrene and starvation groups characterized by a loss of microbial diversity combined with the presence of opportunistic pathogens. Inferred microbial functions enriched in the polystyrene group included transposon movements, membrane restructuring, and adaptations to oxidative stress. We detected several encoded enzymes with reported polystyrene and styrene degradation abilities and provided first insights into involved metabolic pathways, supporting previous reports of polystyrene degrading bacteria in the superworm gut. However, we cannot rule out that the microbiome also metabolized other chemicals, such as flame retardants, present in low concentrations in styrofoam. By recovering metagenome-assembled genomes (MAGs) we linked phylogeny and functions and identified genera, including Pseudomonas, Rhodococcus and Corynebacterium, that possess genes associated with polystyrene degradation. In conclusion, our results demonstrate the survival of superworms on polystyrene feed, however, this diet has considerable negative impacts on gut microbiome diversity and host health.