BbCFEM7 plays an important role in the pathogenicity and gut microbial community formation in the co-infection of Beauveria bassiana with Metarhizium rileyi

ABSTRACT This study investigated the effects of the BbCFEM7 gene in Beauveria bassiana on host pathogenicity and the gut microbial community during co-infection with Metarhizium rileyi in Spodoptera litura . Our results showed that BbCFEM7 significantly enhanced the virulence of B. bassiana and significantly reduced the host LT 50 in the 1:0, 9:1, and 1:1 (Bb:Mr) groups. Sequencing of the gut microbial diversity showed that the presence of BbCFEM7 significantly altered the structure of the host gut microbial community, particularly in the 9:1 group. The presence of BbCFEM7 increased the relative abundance of Enterococcus and decreased that of Thomasclavelia. Furthermore, BbCFEM7 was found to play a pivotal role in enhancing B. bassiana ’s tolerance to chemical stress and promoting its rapid colonization of the host’s hemolymph, thereby giving it an advantage over M. rileyi . These results suggest that BbCFEM7 plays an important role not only in fungal pathogenicity but also in indirectly influencing host health by regulating gut microbial communities. This study provides a new perspective on the interactions between entomopathogenic fungi, hosts, and gut microorganisms and establishes a theoretical basis for optimizing the application of entomopathogenic fungi in pest control. IMPORTANCE This study investigates the role of BbCFEM7 in B. bassiana during co-infection with M. rileyi in S. litura . It reveals that BbCFEM7 significantly enhances fungal pathogenicity, shortens the time taken for the host to die, and alters gut microbial communities. These findings provide novel insights into the interactions between entomopathogenic fungi, hosts, and gut microbes, offering a theoretical basis for optimizing the application of entomopathogenic fungi in pest control, while also contributing to our understanding of the insect microbiome and immunology.