Abstract
SummaryAlmost the entire seafloor is covered with sediments that can be more than 10 000 m thick and represent a vast microbial ecosystem that is a major component of Earth's element and energy cycles. Notably, a significant proportion of microbial life in marine sediments can exploit energy conserved during transformations of sulfur compounds among different redox states. Sulfur cycling, which is primarily driven by sulfate reduction, is tightly interwoven with other important element cycles (carbon, nitrogen, iron, manganese) and therefore has profound implications for both cellular‐ and ecosystem‐level processes. Sulfur‐transforming microorganisms have evolved diverse genetic, metabolic, and in some cases, peculiar phenotypic features to fill an array of ecological niches in marine sediments. Here, we review recent and selected findings on the microbial guilds that are involved in the transformation of different sulfur compounds in marine sediments and emphasise how these are interlinked and have a major influence on ecology and biogeochemistry in the seafloor. Extraordinary discoveries have increased our knowledge on microbial sulfur cycling, mainly in sulfate‐rich surface sediments, yet many questions remain regarding how sulfur redox processes may sustain the deep‐subsurface biosphere and the impact of organic sulfur compounds on the marine sulfur cycle.
Highlights
Marine sediments are dynamic environments that are shaped by interactions among biotic and abiotic processes including the redox reactions by which microorganisms harness energy (Schrenk et al, 2010)
Contemporary research has revealed that remarkably diverse microorganisms have evolved to fulfil an array of niches in marine sediments by transforming sulfur compounds among various redox states (Fig. 1)
From the recent deciphering of the molecular underpinnings of key biochemical pathways for fundamentally important sulfur metabolisms such as sulfate reduction, to developing understandings of the various highly interlinked biogeochemical implications associated with the sulfur cycle, we have acquired a solid grasp about the importance of the sulfur cycle in one of the world’s largest biospheres, i.e. the marine sedimentary seabed
Summary
Almost the entire seafloor is covered with sediments that can be more than 10 000 m thick and represent a vast microbial ecosystem that is a major component of Earth’s element and energy cycles. A significant proportion of microbial life in marine sediments can exploit energy conserved during transformations of sulfur compounds among different redox states. We review recent and selected findings on the microbial guilds that are involved in the transformation of different sulfur compounds in marine sediments and emphasise how these are interlinked and have a major influence on ecology and biogeochemistry in the seafloor. Extraordinary discoveries have increased our knowledge on microbial sulfur cycling, mainly in sulfate-rich surface sediments, yet many questions remain regarding how sulfur redox processes may sustain the deepsubsurface biosphere and the impact of organic sulfur compounds on the marine sulfur cycle
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