Diversification, niche adaptation, and evolution of a novel phylum thriving in the deep Critical Zone

Deep soil is a neglected ecosystem within Earth’s Critical Zone. Our study sheds light on the adaptive traits of a successful bacterial phylum, CSP1-3, which thrives in these energy-limited environments. We document niche specialization and phylogenetic divergence during the evolutionary history of the phylum, revealing its capacities for the carbon, nitrogen, and sulfur cycling. This research enhances our understanding on the survival strategies of microbial life in energy-limited conditions and suggests greater physiological diversification than previously recognized for soil microbiomes. Overall, our study provides insights into the ecology of deep soil microbiomes and emphasizes the importance of deep soil ecosystems in global environmental processes.