title: Calcite-accumulating large sulfur bacteria of the genus Achromatium in Sippewissett Salt Marsh.
abstract: Large sulfur bacteria of the genus Achromatium are exceptional among Bacteria and Archaea as they can accumulate high amounts of internal calcite. Although known for more than 100 years, they remain uncultured, and only freshwater populations have been studied so far. Here we investigate a marine population of calcite-accumulating bacteria that is primarily found at the sediment surface of tide pools in a salt marsh, where high sulfide concentrations meet oversaturated oxygen concentrations during the day. Dynamic sulfur cycling by phototrophic sulfide-oxidizing and heterotrophic sulfate-reducing bacteria co-occurring in these sediments creates a highly sulfidic environment that we propose induces behavioral differences in the Achromatium population compared with reported migration patterns in a low-sulfide environment. Fluctuating intracellular calcium/sulfur ratios at different depths and times of day indicate a biochemical reaction of the salt marsh Achromatium to diurnal changes in sedimentary redox conditions. We correlate this calcite dynamic with new evidence regarding its formation/mobilization and suggest general implications as well as a possible biological function of calcite accumulation in large bacteria in the sediment environment that is governed by gradients. Finally, we propose a new taxonomic classification of the salt marsh Achromatium based on their adaptation to a significantly different habitat than their freshwater relatives, as indicated by their differential behavior as well as phylogenetic distance on 16S ribosomal RNA gene level. In future studies, whole-genome characterization and additional ecophysiological factors could further support the distinctive position of salt marsh Achromatium.
authors.affiliation: Department of Microbiology, Cornell University, Ithaca, NY, USA.|Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Verena
authors.initials: V
authors.lastname: Salman
authors.affiliation: Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Tingting
authors.initials: T
authors.lastname: Yang
authors.affiliation: Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Tom
authors.identifier: http://orcid.org/0000-0003-1833-8731
authors.initials: T
authors.lastname: Berben
authors.affiliation: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
authors.forename: Frieder
authors.initials: F
authors.lastname: Klein
authors.affiliation: Department of Microbiology, Cornell University, Ithaca, NY, USA.
authors.forename: Esther
authors.initials: E
authors.lastname: Angert
authors.affiliation: Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Teske
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D017610:Calcium Compounds; D005618:Fresh Water / Q000382:microbiology*; D020563:Gammaproteobacteria / Q000235:genetics; D006088:Gram-Negative Aerobic Bacteria / Q000235:genetics*; D008404:Massachusetts; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012965:Sodium Chloride; D013440:Sulfides; D013455:Sulfur / Q000737:chemistry; D016999:Sulfur-Reducing Bacteria / Q000235:genetics*; D014871:Water Microbiology; D053833:Wetlands
chemical_list: D017610:Calcium Compounds; D012336:RNA, Ribosomal, 16S; D013440:Sulfides; C033907:calcium sulfide; D012965:Sodium Chloride; D013455:Sulfur; D002119:Calcium Carbonate