Comparative Analysis of Proteolytic Enzyme Activity in the Midgut of Galleria mellonella Larvae Selected for Antibiotic Resistance

The accumulation of antibiotics in biocoenoses poses risks for the development of multidrug-resistant microorganisms through horizontal transfer of resistance genes and metabolic changes in various animals, including humans. These changes may affect the structure of digestive enzymes in the gut by switching between different classes and isoforms of proteases, expressing new isoforms, and significantly impacting digestion and pathogen resistance. This study was conducted on larvae of the greater wax moth Galleria mellonella, which were cultured on a diet containing low doses of an antibiotic for thirty generations (R-strain). The resulting R-strain demonstrated significant resistance of these insects to the entomopathogenic bacteria Bacillus thuringiensis (Bt). Infection of R-strain insects with Bt showed a complete loss of larval susceptibility to the bacteria and a reduction in overall proteolytic enzyme activity from the first day post-treatment, primarily due to the suppression of serine protease activity.