Unravelling the ultramafic rock-driven serpentine soil formation leading to the geo-accumulation of heavy metals: An impact on the resident microbiome, biogeochemical cycling and acclimatized eco-physiological profiles

In the present study, we have underpinned the serpentine rock, serpentinized ultramafic soil and rhizosphere's microbial communities, signifying their heavy metals-exposed taxa signatures and functional repertoires in comparison to non-serpentine soils. The results revealed that the serpentine rock embedded soil highlighted the geo-accumulation of higher amount of Cr and Ni impacting soil microbial diversity negatively by metal stress -driven selection. Biolog Ecoplate CLPP defined a restricted spectrum of C-utilization in the higher heavy metal-containing serpentine samples compared to non-serpentine. The linear discriminant analysis (LDA) score identified a higher abundance of Desulfobacterota, Opitutales, and Bacteroidales in low Cr and Ni-stressed non -serpentine-exposed samples. Whereas the abundance of Propionibacteriales and Actinobacteriota were signifi-cantly enriched in the serpentine niche. Further, the C, N, S, Fe, and methane biogeochemical cycles linked functional members were identified, and showing higher functional diversity in low Cr and Ni concentration -containing rhizosphere JS-soils. The Pearson correlation coefficient (r) value confirmed the abundance of functional members linked to specific biogeochemical cycle, positively correlated with relevant pathway enrichment. Ultimately, this study highlighted the heavy metal stress within a serpentine setting that could limit the resident microbial community's metabolic diversity and further select the bacteria that could thrive in the serpentine-associated heavy metal-stressed soils. These acclimatized microbes could pave the way for the future applications in the soil conservation and management.