Metaproteomics and metagenomics analysis reveal distinct metabolic and adaptive functions of euphotic and bathypelagic microbial communities in the South China Sea

Marine microorganisms inhabiting the bathypelagic zone (1000 m - 4000 m) are pivotal to biogeochemical cycling. However, a comprehensive understanding of microbial community structure and their metabolic activities adaptations to the extreme deep-sea conditions remains elusive. In this study, we employed a metaproteomic approach to investigate the protein profiles of microbial communities spanning the surface and bathypelagic layers of the South China Sea (SCS) and performed a comparative analysis with metagenomic data. The metaproteome and metagenome showed low correlation in functional expression but a high correlation at the phylum level. High-abundance genes were more likely to be translated into proteins, with protein over-representation observed in energy conversion and matter transport processes. Short-chain amide porins facilitate substance exchange and maintain cellular homeostasis, enabling Methylococcales to adapt to deep-sea conditions and actively oxidize methane. Flexible energy utilization strategies, such as CO oxidation, enable Propionibacteriales to thrive in deep-sea environments. This study highlights the significance of microbial enzyme resources and offers valuable insights into the adaptations of deep-sea microorganisms, emphasizing their considerable application potential.