Role of the intestinal microbiome in polyethylene degradation by caterpillar larva of the greater wax moth (Galleria mellonella)

Recently, a few insects, including the caterpillar larva of the greater
wax moth Galleria mellonella, have been identified as avid
"plastivores". Interestingly, these caterpillars are able to
ingest and metabolize polyethylene at unprecedented rates. While it
appears that G. mellonella plays an important role in the biodegradation
process, the contribution of its intestinal microbiome remains poorly
understood and contested. In a series of experiments, we present strong
evidence of an intricate relationship between an intact microbiome, low
density polyethylene (LDPE) biodegradation, and the production of glycol
as a metabolic by-product. First, we biochemically confirmed that G.
mellonella larvae consume and metabolize LDPE, as individual caterpillars
fed on polyethylene excreted glycol, but those excretions are reduced by
antibiotic treatment. Further, while the gut bacterial communities remain
relatively stable regardless of diet, we show that during the early phases
of feeding on LDPE (24-72 hrs), caterpillars exhibit increased microbial
abundance relative to those starved or fed on their natural honeycomb
diet. Finally, by isolating and growing gut bacteria with polyethylene as
their exclusive carbon source for over one year, we identified
microorganisms in the genus Acinetobacter that appear to be involved in
this biodegradation process. Taken collectively, our study indicates that
during short term exposure, the intestinal microbiome of G. mellonella is
intricately associated with polyethylene biodegradation in vivo.