title: A new addition to the cell plan of anammox bacteria: "Candidatus Kuenenia stuttgartiensis" has a protein surface layer as the outermost layer of the cell.
abstract: Anammox bacteria perform anaerobic ammonium oxidation (anammox) and have a unique compartmentalized cell consisting of three membrane-bound compartments (from inside outwards): the anammoxosome, riboplasm, and paryphoplasm. The cell envelope of anammox bacteria has been proposed to deviate from typical bacterial cell envelopes by lacking both peptidoglycan and a typical outer membrane. However, the composition of the anammox cell envelope is presently unknown. Here, we investigated the outermost layer of the anammox cell and identified a proteinaceous surface layer (S-layer) (a crystalline array of protein subunits) as the outermost component of the cell envelope of the anammox bacterium "Candidatus Kuenenia stuttgartiensis." This is the first description of an S-layer in the phylum of the Planctomycetes and a new addition to the cell plan of anammox bacteria. This S-layer showed hexagonal symmetry with a unit cell consisting of six protein subunits. The enrichment of the S-layer from the cell led to a 160-kDa candidate protein, Kustd1514, which has no homology to any known protein. This protein is present in a glycosylated form. Antibodies were generated against the glycoprotein and used for immunogold localization. The antiserum localized Kustd1514 to the S-layer and thus verified that this protein forms the "Ca. Kuenenia stuttgartiensis" S-layer.
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Faculty of Science, Radboud University Nijmegen, Nijmegen, the Netherlands.
authors.forename: Muriel C F
authors.initials: MC
authors.lastname: van Teeseling
authors.forename: Naomi M
authors.initials: NM
authors.lastname: de Almeida
authors.forename: Andreas
authors.initials: A
authors.lastname: Klingl
authors.forename: Daan R
authors.initials: DR
authors.lastname: Speth
authors.forename: Huub J M
authors.initials: HJ
authors.lastname: Op den Camp
authors.forename: Reinhard
authors.initials: R
authors.lastname: Rachel
authors.forename: Mike S M
authors.initials: MS
authors.lastname: Jetten
authors.forename: Laura
authors.initials: L
authors.lastname: van Niftrik
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism; D001419:Bacteria / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D008562:Membrane Glycoproteins / Q000032:analysis*; D008854:Microscopy, Electron; D010084:Oxidation-Reduction; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism
chemical_list: D064751:Ammonium Compounds; D008562:Membrane Glycoproteins; D021122:Protein Subunits; C055764:S-layer proteins