Intestinal probiotics restore the ecological fitness decline of <i>Bactrocera dorsalis</i> by irradiation

Abstract

The sterile insect technique (SIT) as an eco-friendly and reliable strategy has been used to control populations of insect pests of agricultural, veterinary and human health importance. Successful applications of SIT rely on the high-level ecological fitness of sterile males. A suitable and stable gut microbiome can contribute to the ecological fitness of insect by influencing their physiology, biochemistry and development processes. Here, we show that a shift in the gut bacterial composition and structure by sterilizing irradiation, characterized by a decrease in the major gut microbiota community Enterobacteriaceae, an expansion of the minor members (e.g., Bacillaceae) and a higher richness and diversity, is tightly linked to radiation-induced ecological fitness (male mating competitiveness, flight capacity, survival rate and life span) decline in <i>Bactrocera dorsalis</i> (Hendel) sterile males. Function prediction of gut microbiota indicated that changes in microbiome taxonomy tend to drive microbiome functional shifts. A higher nutrient consumption of the flourishing minor gut microbiota may cause a decline in nutrients and energy metabolic activity of host and then result in the reduced ecological fitness of irradiated flies. Furthermore, we found that a gut bacterial strain <i>Klebsiella oxytoca</i> (BD177) can restore ecological fitness by improving food intake and increasing haemolymph sugar and amino acid levels of irradiated <i>B. dorsalis</i> flies. Our findings suggest that gut symbiont-based probiotics can be used as agents for reversing radiation-induced ecological fitness decrease.