Endobacteria Have a Negative Effect on the Virulence of Metarhizium

Most organisms are associated with microorganisms, which influence their behavior during their life cycles. Fungi are no exception; they interact with plants, viruses, and bacteria in various environments, forming complex communities. These associations can occur externally around the mycelia and internally within the hyphae. Fungi can harbor bacteria, mycoviruses, and other fungi within their hyphae. Some endobacteria (EB) have been shown to alter fungal host function, development, and interactions with other organisms. Most fungi that host endobacteria (EB) are plant-associated. Although members of the genus <i>Metarhizium</i> are among the most abundant fungi isolated from soils, their associated EB have not been sufficiently studied. Endobacteria were recently detected in <i>M. bibiondarum</i> and <i>M. anisopliae</i>; however, the biological roles of these bacteria in the different <i>Metarhizium</i> life cycles remain unknown. In this study, <i>Metarhizium</i> strains were isolated from the rhizosphere and <i>Phyllophaga</i> spp. <i>Bacillus subtilis</i> was identified as an endobacterium, and its influence on the physiology of <i>Metarhizium</i> and entomopathogenic capacity was studied. Our analysis revealed that EB have a negative impact on the virulence of <i>Metarhizium</i> against <i>Galleria mellonella</i> and <i>Tenebrio molitor.</i>