Characterization of the gut microbes of greater wax moth (Galleria mellonella Linnaeus) shows presence of potential polymer degraders.

Abstract

Greater wax moth (GWM), Galleria mellonella (Lepidoptera: Pyralidae), is a highly destructive honey bee pest prevalent throughout the world. It is considered as a major factor to the alarming decline in honey bee population. GWM destroys active honey combs as it feeds on the beeswax andlays eggs in bee hives, and the primary food of their larva is beeswax. Beeswax is a polymer composed mainly of saturated and unsaturated, linear and complex monoesters, and hydrocarbons. The most frequent bond in beeswax is ethene (CH2-CH2) which is also found in the common plastic polyethylene. As wax-digestion is not a common animal character, we hypothesized about a possible role of GWM gut microflora in the process; which could possibly degrade polyethylene-like polymers as well. This study was aimed to identify the GWM gut microflora via culture-dependant approach. We characterized several bacterial species based on the culture characteristics, Gram-reaction, and various biochemical tests. Sequencing of 16S-rDNA revealed nine bacterial and one microalgal species from GWM gut. The bacterial species included Gram-positive Exiguobacterium aestuarii, Bacillus circulans, Microbacterium zaea, Microbacterium sp. and Enterococcus faecalis; Gram-negative Agrobacterium sp., Sphingomonas pseudosanguinis, Sphingobium yanoikuyaeand Acinetobacter radioresistens;the microalgae was Picochlorum oklahomensis. Some of them have been previously reported to degrade polycyclic aromatic hydrocarbon, low-density polyethylene, and 2-methylphenanthrene. Meanwhile, the microalga, P. oklahomensis, was reported to steal bacterial genes to adapt with abiotic stresses. Further investigation is necessary to explore the precise details about polymer degrading capabilities of these microbes; nevertheless, this study builds a foundation for elaborate and advanced future research.