Acinetobacter bacteria could be potent degraders of fragmented polyethylene and polypropylene among the digestive tract bacteria of Galleria waxworms

Polyethylene (PE) and polypropylene (PP) dominate plastic production and are seriously contaminating environments. Bacteria in PE- and PP-ingesting worms, including Galleria, have thus attracted considerable attention owing to their PE and PP biodegradation potential and were investigated in this study. As PE and PP may be biodegraded after fragmented, the bacteria were enriched on n-hexadecane (a PE fragment) and on pristane (a branched alkane structurally similar to PP fragments) from the digestive tracts of Galleria waxworms. In these enriched cultures, Acinetobacter bacteria, particularly Acinetobacter courvalinii, Acinetobacter calcoaceticus, and Acinetobacter pittii, were detected most abundantly (A. calcoaceticus is closely related to A. pittii). Two alkane degraders probably of A. courvalinii and A. pittii were isolated from the cultures. They also degraded liquid PP (PP fragments), but not as a sole carbon source, and preferred different alkane chain lengths. On solid PE and PP, only initial signs of degradation (oxidation) were detected with each isolate. Surprisingly, the Acinetobacter bacteria were naturally abundant in the intestine of a ghostshark that contains much diacyl glyceryl ethers in its liver. These results indicate that Acinetobacter could be potent degraders of alkyl chains, including PE and PP fragments, among digestive tract bacteria of some terrestrial and marine organisms, including PE- and PP-ingesting worms.