Metagenomic and metatranscriptomic analysis reveal genetic adaptation of deep-sea microbial communities

The water body underlying the photic zone in oceans represents the largest water mass on earth (comprising 1.3×10¹⁸ m³), and is also the largest aqueous habitat for various microorganisms. This realm differs distinctly from the photic zone, in terms of its relatively lower temperature (approximately 2~4°C), higher pressure and richer inorganic nutrients. Differences in physical geochemical parameters between uppersea and deep-sea environments create fundamentally different challenges to microbial communities living in these environments. Recent studies found that prokaryotic microbes in deep-sea environments are welladapted to the special dwelling environments after long evolution, carrying genetic features that enable them to live and reproduce in the extreme environmental conditions. Recent progress in sequencing technologies is fueling a rapid increase in the number and scope of deepsea microbial community-targeted studies. While metagenomic analysis can provide information on the taxonomic composition and metabolic potential of microbial communities in the deep sea, metatranscriptomics serves to unveil the actual metabolic activities of the communities at a specific time and location, and how those activities are changing in response to environmental and biotic challenges. Here we provide a summary of recent progress in applying integrated metagenomic and metatranscriptomic analyses to uncover the special genetic features in the well-adapted deep-sea microbial communities.