A non-redundant genomic catalog of the class UBA4738 within the phylum Actinomycetota.

Terrestrial deep soils are vast, oligotrophic habitats. This study reveals the adaptive strategies of UBA4738, a dominant bacterial class in these environments. Despite its streamlined genome (small size, high GC content, and low C/N-ratio proteins), UBA4738 possesses high metabolic flexibility to utilize diverse energy sources. Notably, evolutionary analyses show that UBA4738 acquired predatory traits (e.g., Tad/Type IV pili and pore-forming toxins) through functional expansion during adaptation to oligotrophy. This lineage represents a unique survival paradigm that balances genome streamlining with functional complexity, expanding our understanding of microbial adaptive evolution under extreme resource constraints.