Comprehensive in silico analysis of eggNOG-annotated orthologous genes infers functional dynamics and energy metabolism in the microbiome of Abutilon fruticosum

Abutilon fruticosum is an ecologically and pharmacologically important wild Malvaceae species whose rhizospheric microbiome remains poorly resolved at the level of orthologous-group (OG) genes. Shotgun metagenomic sequencing and eggNOG/COG-based annotation were used to compare rhizosphere and bulk-soil microbiomes, quantify OG repertoires, and infer in silico functional modules. Principal coordinate and Bray–Curtis analyses of COG categories revealed clear functional segregation between rhizosphere and bulk communities, with the rhizosphere enriched in high-abundance OGs linked to energy metabolism, nutrient transport, stress response, and secondary metabolism. Computational ranking identified a cohort of highly recurrent OGs, predominantly associated with Actinobacteria and Proteobacteria but also with Streptophyta, that dominate the predicted functional landscape and are markedly more abundant in silico in rhizospheric soil. Using eggNOG/COG assignments, ten interacting putative functional modules were delineated in silico, encompassing NADH–quinone oxidoreductase–centered bioenergetics, ABC-type nitrogen and sulfur acquisition, fatty-acid and propionate catabolism, sulfur scavenging and detoxification, cell-envelope and biofilm formation, multidrug efflux, DNA maintenance, environmental sensing and transcriptional regulation, specialized competition/protection, and mobile genetic elements. Conceptual, hypothesis-generating frameworks integrating selected modules posit that rhizosphere dominance could arise from the coordinated coupling of ATP/proton motive force (PMF) generation with high-affinity nutrient uptake, sulfur and carbonyl detoxification, iron-sequestering and antioxidant secondary metabolism, and stress-responsive multidrug efflux, based on our analyses. These predictions suggest that specific OG cohorts act as keystone energetic, metabolic, and defense hubs in the A. fruticosum rhizosphere and provide testable hypotheses for future experimental work linking module-level functions to root colonization, stress tolerance, and plant performance. (249 words)