Britt Abrahamson (@brittabrahamson.bsky.social)

Novel insights into microbial DMSP/DMS cycling: from surface to deep ocean | mBio The organic sulfur cycle, centered around dimethylsulfoniopropionate (DMSP) and its climatically active metabolite dimethyl sulfide (DMS) (1), is a complex and dynamic component of global sulfur cycling, involving biochemical transformations of diverse organosulfur compounds. Since algae were considered to be the dominant producers of abundant DMSP in the ocean (2), research has primarily focused on the upper ocean layers, where massive DMSP production by algae and its subsequent microbial conversion to DMS were established as key processes. While the significance of DMSP/DMS-related organic sulfur cycling has been recognized, it was largely limited to the euphotic zones. The vast dark ocean, representing over 90% of the ocean volume (3), has traditionally been viewed as a major reservoir for exported organic matter, where organosulfur compounds are rapidly processed and largely remineralized back to sulfate through microbially mediated transformations (4, 5). However, intermediate transformations within the organic sulfur pool and release of DMS in the deep oceans remain poorly understood (5). Recent discoveries from the deep sea, including hadal trenches and abyssal sediments, have revealed not only detectable concentrations of DMSP in these extreme environments, but more importantly, an unexpected genetic and metabolic capacity for organic sulfur cycling among deep-sea microbes (6–9). This emerging evidence, including the direct detection of DMSP and the widespread occurrence of genes and metabolic pathways involved in the conversion of organic sulfur compounds, suggests that the deep ocean represents an active, metabolically distinct environment where microbes drive organosulfur transformation. This review aims to summarize these recent discoveries, delineating how deep-sea microbes drive a unique sulfur cycle network and elucidating the potential influence of this previously hidden process on global sulfur fluxes. https://journals.asm.org/doi/10.1128/mbio.01207-26