Dissemination patterns and functional role of a symbiotic bacteria Stenotrophomonas maltophilia in Phytoseiulus persimilis

Symbiotic bacteria play a crucial role in various facets of host biology and physiology. The development and utilization of symbiotic bacteria in insects show promising potential for enhancing their reproduction, temperature tolerance, resistances to pathogens and insecticides. However, limited research has been conducted on symbiotic bacteria in predatory mites. In Phytoseiulus persimilis, we successfully cultivated a strain of Stenotrophomonas maltophilia, which has been noted for its significant contributions to pathogen control, pesticide and toxin resistance, and nutrition provision in some insect species. To explore the effect of S. maltophilia and its potential application on predatory mites, we fed S. maltophilia to P. persimilis and evaluated the transmission dynamics within mite generations. We examined its impacts on predator fitness and resistances to pesticides, pathogens, and starvation. The results showed that the S. maltophilia content in the offspring increased by 12.91 times when gravid mites were fed with the bacterial solution. P. persimilis that consumed prey treated with S. maltophilia showed a 25.20-fold increase in microbial content. Mating with treated males did not affect microbial levels in females. Moreover, S. maltophilia did not cause any discernible effect on the fitness of P. persimilis, including survival, developmental duration, fecundity, and longevity. Notably, it was found to improve P. persimilis survival following exposure to the pathogen Acaricomes phytoseiuli, resulting in a reduction of mortality by 20% compared to the control. This study serves as a foundational step for further utilization of beneficial microbes to improve the efficacy of predatory mite biological control.