Deciphering common bean (Phaseolus Vulgaris L.) microbiome assemblages reveal mechanistic insights into host-pathogen-microbiome interactions

Abstract

Common bean (Phaseolus vulgaris L.) is the primary source of proteins and nutrients in most households in sub-Saharan Africa. However, production of this crop is constrained by several biotic factors. While research on common bean plant-pathogen interactions has predominantly focused on binary relationships, the diversity of microbes naturally inhabiting plant tissues and their interactions has often been overlooked. Recent findings, however, show that these resident microbes actively contribute to plant defense mechanisms, rather than merely acting as passive bystanders. This study aimed to document and explore potential interactions within the common bean microbiome assemblages through field investigations in selected locations across the western regions of Kenya. Common bean leaf samples were collected from farmer's fields along motorable roads 3–5 km apart. Shotgun metagenomic analysis identified a diverse range of microorganisms, including bacteria, fungi, yeast, phytoplasmas, viruses, and bacteriophages, across multiple taxonomic levels—spanning 4 Kingdoms, 136 Phyla, 168 Classes, 360 Orders, 792 Families, 2039 Genera, and 6130 Species—both epiphytic and endophytic, and pathogenic or non-pathogenic. Pseudomonadota consistently showed the highest taxonomic annotation for antimicrobial-resistant organisms, highlighting its central role in resistance across the studied area. The sequences obtained were mapped to the EggNOG, CAZy, and KEGG databases to explore, assign, and predict gene functions. The EggNOG database emphasized the importance of “Replication, recombination, and repair” processes in maintaining genomic stability, along with amino acid transport, energy production, and metabolism. CAZy analysis revealed a significant presence of glycosyltransferases, particularly from GT1 and GT32 families, and noted the role of enzymes like Glycoside Hydrolases in plant defense against pathogens. KEGG pathway analysis underscored the central role of metabolic processes such as energy metabolism, translation, and carbohydrate metabolism. Key pathways linked to plant defense and resilience, including 2-oxocarboxylic acid metabolism, amino acid biosynthesis, and secondary metabolite biosynthesis, were identified. These findings underscore the role of metabolic and enzymatic processes in strengthening plant defenses and stress tolerance while laying the groundwork for multidisciplinary research to advance sustainable agriculture and food safety.