A Diet with Amikacin Changes the Bacteriobiome and the Physiological State of Galleria mellonella and Causes Its Resistance to Bacillus thuringiensis

SIMPLE SUMMARY: The insect gut microbiota plays a crucial role in the host’s resistance to pathogenic microorganisms and toxins. Resident microorganisms may persist for a long time and maintain a certain location due to the synthesis of antimicrobial agents (including antibiotics). We consider it one of the adaptation mechanisms of microorganisms in various communities. Not only do the uncontrolled use of antibiotics and changes in environmental conditions drastically alter the microbiota structure and give rise to resistant microorganisms, but they also cause a number of alterations in the host’s physiology and its sensitivity to pathogens. This study opens up new prospects for further research into antibiotic-resistant symbiotic microorganisms, their benefits for persistence in the dynamic environment of the insect’s gut, and the conditions necessary for changing their strategy and manifestation of virulent properties. ABSTRACT: Environmental pollution with antibiotics can cause antibiotic resistance in microorganisms, including the intestinal microbiota of various insects. The effects of low-dose aminoglycoside antibiotic (amikacin) on the resident gut microbiota of Galleria mellonella, its digestion, its physiological parameters, and the resistance of this species to bacteria Bacillus thuringiensis were investigated. Here, 16S rDNA analysis revealed that the number of non-dominant Enterococcus mundtii bacteria in the eighteenth generation of the wax moth treated with amikacin was increased 73 fold compared to E. faecalis, the dominant bacteria in the native line of the wax moth. These changes were accompanied by increased activity of acidic protease and glutathione-S-transferase in the midgut tissues of larvae. Ultra-thin section electron microscopy detected no changes in the structure of the midgut tissues. In addition, reduced pupa weight and resistance of larvae to B. thuringiensis were observed in the eighteenth generation of the wax moth reared on a diet with amikacin. We suggest that long-term cultivation of wax moth larvae on an artificial diet with an antibiotic leads to its adaptation due to changes in both the gut microbiota community and the physiological state of the insect organism.