Summary Chemoautotrophic bacteria belonging to the genus Sulfurimonas (class Campylobacteria ) were previously identified as key players in the turnover of zero‐valence sulfur, a central intermediate in the marine sulfur cycle. S. denitrificans was further shown to be able to oxidize cyclooctasulfur (S 8 ). However, at present the mechanism of activation and metabolism of cyclooctasulfur is not known. Here, we assessed the tra...

Summary Coastal oceans receive large amounts of anthropogenic fixed nitrogen (N), most of which is denitrified in the sediment before reaching the open ocean. Sandy sediments, which are common in coastal regions, seem to play an important role in catalysing this N‐loss. Permeable sediments are characterized by advective porewater transport, which supplies high fluxes of organic matter into the sediment, but also leads to fluct...

Summary Molecular hydrogen (H 2 ) is the key intermediate in the anaerobic degradation of organic matter. Its removal by H 2 ‐oxidizing microorganisms is essential to keep anaerobic degradation energetically favourable. Sulfate‐reducing microorganisms (SRM) are known as the main H 2 scavengers in anoxic marine sediments. Although the community of marine SRM has been extensively studied, those consuming H 2 in situ are complete...

Summary Among the dominant deltaproteobacterial sulfate‐reducing bacteria ( SRB ), members of the genus D esulfobacula are not only present in (hydrocarbon‐rich) marine sediments, but occur also frequently in the anoxic water bodies encountered in marine upwelling areas. Here, we present the 5.2 Mbp genome of D esulfobacula toluolica Tol2 , which is the first of an aromatic compound‐degrading, marine SRB . The genome has appar...

Summary Members of the Bacteroidetes , formerly known as the Cytophaga‐Flavobacteria‐Bacteroides (CFB) phylum, are among the major taxa of marine heterotrophic bacterioplankton frequently found on macroscopic organic matter particles (marine snow). In addition, they have been shown to also represent a significant part of free‐living microbial assemblages in nutrient‐rich microenvironments. Their abundance and distribution patt...