The Bacterial and Fungal Gut Microbiota of the Greater Wax Moth, Galleria mellonella L. Consuming Polyethylene and Polystyrene

Abstract

Plastic production has been increasing exponentially in the last 60 years, but plastic disposal is out of control, resulting in the pollution of all ecosystems on Earth. Finding alternative environmentally sustainable choices, such as biodegradation by insects and their associated gut microbiota, is crucial, however we have only begun to characterize these ecosystems. Some bacteria and one fungus have been previously identified in the gut of Greater Wax Moth larvae (Galleria mellonella L., Lepidoptera, Pyralidae) located mainly in the Northern hemisphere. The aim of this study was to describe changes in the gut microbiota associated with the consumption of polyethylene and polystyrene by the Greater Wax Moth in Argentina, considering both bacteria and fungi. Larvae were fed polyethylene, polystyrene and beeswax as control for 7 days. Next generation sequencing revealed changes in the bacterial gut microbiome of the wax moth larvae at the phyla and genus levels, with an increase in two Pseudomonas strains. The fungal communities showed no differences in composition between diets, only changing in relative abundance. This is the first report of both bacterial and fungal communities associated with a plastivore insect. The results are promising and call for more studies concerning a potential multi-kingdom synergy in the plastic biodegradation process.

Keywords: Argentina; bacteria; fungi; insect gut; plastic pollution; plastivore.

Figure 1

Beta diversity (NMDS) of bacterial (A) and fungal (D) communities. Species Richness based on Shannon (B) and Chao diversity indexes for bacterial (B,C) and fungal (E,F) communities with statistical significance value calculated through Wilcoxon pairwise test.

Figure 2

Composed panel depicting taxonomic plots of bacterial diversity at the phyla level (A) and genus level (B). Plots corresponding to fungal diversity at the phyla (C) and genus level (D). The legend shows the taxa with more than 1% of abundance.

Figure 3

Ubiquity analysis of both bacterial and fungal biomes comparing relative abundance against prevalence in samples based on plastic material used for treatment.

Figure 4

Biomarker discriminant taxa analyses of bacterial communities according to the treatment, via LEfSe (Linear discriminant analysis Effect Size) algorithm, including only OTUs present in at least 50% of the samples. Values of p are in some taxa added to the plot.

Figure 5

Biomarker discriminant taxa analyses of fungal communities according to the treatment, via LEfSe, including only OTUs present in at least 50% of the samples. Taxa shown here correspond to genus level or to the lowest unclassified taxa. values of p are in some taxa added to the plot.

Figure 6

Co-occurrence analysis heat map showing the degree of association between bacteria and fungi taxa across diets, scored using the Dice index. Clustering obtained from Euclidean distances between taxa. (A): beeswax, (B): polyethylene, (C): expanded polystyrene.