Cumulative adult production and aerobic culture-dependent recovery of gut-associated bacteria in Galleria mellonella maintained on polymer-containing diets.

Growing interest in insects capable of developing in the presence of synthetic polymers has created new opportunities to investigate host responses alongside cultivable gut microorganisms. This study evaluated cumulative adult production in Galleria mellonella maintained on a control diet or diets containing polyethylene terephthalate (PET), polystyrene (PS), or polyethylene (PE), together with the recovery of bacteria from the larval gut. Four dietary treatments control, PET, PS, and PE were established, each with five replicates of 15 initial larvae. Each experimental colony remained on its assigned diet until the initial cohort completed its life cycle and produced a second generation. Larvae from this offspring generation were selected for bacterial isolation, while the remaining individuals continued development for measurement of cumulative adult production. The isolates were characterized by sequencing the V4 region of the 16S rRNA gene and comparison using BLASTn, followed by genus-level taxonomic assignment. Cumulative adult production in the second generation differed among treatments (P = 0.0194). The control produced the highest mean number of adults (122.0 ± 56.3), whereas PET produced the lowest (41.8 ± 19.1) and was the only treatment significantly lower than the control. Fourteen bacterial isolates, selected as representatives of visually distinct colony morphotypes, were characterized; these isolates were not assumed to represent 14 distinct taxa or strains. Thirteen were assigned to Bacillus and one to Psychrobacillus. Overall, the dietary formulations evaluated were associated with variation in cumulative adult production and yielded an initial collection of cultivable gut-associated bacteria for subsequent bioprospecting studies.