Unravelling the genomic and functional arsenal of Bacilli endophytes from plants with different lifestyles

Abstract

Endophytic microbiomes of crop wild relatives (CWRs) adapted to extreme environments, such as halophytes, are promising sources of plant-beneficial bacteria and secondary metabolites for sustainable food production. Here, we analyzed 25 Bacilli isolates obtained from CWRs, halophytes, and other plant species in Crete, Greece. Using a hybrid Illumina-PacBio sequencing approach, we generated high-quality genomes and performed comparative genomics, phylogenetic, and pangenome analyses, complemented by in vitro assays. We identified 312 biosynthetic gene clusters (BGCs), nearly 60% of which showed no similarity to known clusters, revealing extensive unexplored biosynthetic potential. These unique BGCs may constitute an adaptive feature enabling endophytic Bacilli to colonize and interact with host plants. The isolates spanned diverse genera (Bacillus, Paenibacillus, Peribacillus, Neobacillus, Cytobacillus, Rossellomorea), including three novel species. Phenotypic assays of our isolates demonstrated high salinity tolerance (up to 17.5% w/v NaCl) and strong antagonism against major bacterial and fungal phytopathogens. Genome mining further revealed a broad array of putatively plant-beneficial traits related to growth promotion, stress adaptation, host interaction and inhibition of pathogens. Together, these findings show that Bacilli endophytes from wild and halophytic plants possess exceptional phylogenetic novelty, functional diversity, and biosynthetic capacity, providing new genomic and ecological insights into Bacilli associated with plants inhabiting extreme environments.