Metabolically diverse microorganisms mediating hydrocarbon cycling in the subseafloor sediment of the Challenger Deep

, suggests that hadal heterotrophic microorganisms may synthesize hydrocarbons. These findings provide evidence for microbial hydrocarbon production and thereby support a previously unrecognized sedimentary hydrocarbon cycle.IMPORTANCEOur findings suggest that hydrocarbon degradation may play an important role in organic matter decomposition and carbon cycling in the hadal subseafloor. This degradation capacity is likely distributed through diverse metabolic pathways across a wide range of phylogenetic taxa. The detection of genes likely encoding enzymes involved in aerobic and anaerobic hydrocarbon degradation, as well as the identification of novel hydrocarbon-degrading (HYD) phyla, highlights the complexity and significance of microbial processes in hadal subsurface sediment. The widespread distribution of hydrocarbon degradation capacity in different hadal sediments suggests hydrocarbons as a potential carbon source sustaining microbial life in this extreme environment. Moreover, the presence of genes associated with hydrocarbon synthesis suggests that hadal sediment microbes possess the genetic potential for both degrading and producing hydrocarbons, pointing to a dynamic and multifaceted hydrocarbon cycle within hadal subsurface sediment.