The life sulfuric: microbial ecology of sulfur cycling in marine sediments

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.

Bacterial interactions during sequential degradation of cyanobacterial necromass in a sulfidic arctic marine sediment

“…S5), which besides sulfate can also use nitrate, sulfite and thiosulfate as electron acceptor (Lie et al, 1999). Iron and nitrate reduction contribute to organic carbon oxidation in Svalbard fjord sediments (Kostka et al, 1999;Finke et al, 2007;Canion et al, 2014) and many SRM use intermediate sulfur species for respiration (Wasmund et al, 2017). Thus, iron, nitrate or intermediate sulfur species might have been utilized by the phylotypes that were not inhibited by molybdate.…”

Microbial diversity and metabolic potential in cyanotoxin producing cyanobacterial mats throughout a river network

“…Their identification in mats in a river network suggests that they play important and previously unrecognized roles in aquatic biofilms, both via carbon turnover and impacts on host organisms. Many Cyanobacteria and Proteobacteria contain genes for sulfur and sulfide oxidation, both of which can occur in oxygenated environments, but often in proximity to anoxic regions where reduced sulfur compounds are formed or accumulate (Wasmund et al, 2017). However, most rivers do not have high concentrations of elemental or reduced sulfur in the water column (Meybeck, 1993).…”

PeatlandAcidobacteriawith a dissimilatory sulfur metabolism

“…The capability for characteristic sulfur redox reactions such as dissimilatory sulfate reduction or sulfide oxidation is not confined to single taxa but distributed across different, often unrelated taxa. The true extent of the taxon-diversity within the different guilds of sulfur microorganisms is unknown (Wasmund et al, 2017). However, ecological studies employing specific sulfur metabolism genes (e.g., dissimilatory adenylyl-sulfate reductaseencoding aprBA, dissimilatory sulfite reductase-encoding dsrAB, or soxB that codes for a part of the thiosulfate-oxidizing Sox enzyme machinery) as phylogenetic and functional markers have repeatedly demonstrated that only a minor fraction of the sulfur metabolism gene diversity in many environments can be linked to recognized taxa (Meyer et al, 2007;Müller et al, 2015;Watanabe et al, 2016).…”