title: Distribution, ecology and molecular identification of Thioploca from Danish brackish water sediments.
abstract: The distribution of Thioploca populations was investigated in Danish fjords, brackish lakes and coastal waters. Thioploca was found in three geographically distinct populations, where biomasses reached 33.8+/-14.3 g wet weight m(-2) (mean+/-SD). Mats or lawns were not formed at the sediment surfaces and Thioploca biomasses peaked 4-7 cm into the sediment and extended down to 18 cm depth. Morphology and 16S rRNA gene sequences classified all populations as Thioploca ingrica. A sequence divergence of 1.7-2.2% indicated that T. ingrica comprise at least two genotypes. Physiological analysis showed that T. ingrica accumulate nitrate in concentrations of approximately 3 mM and that bicarbonate and acetate are used as a carbon source. The presence of oxygen promoted carbon incorporation, but T. ingrica could survive up to 3 months without an external supply of nitrate or oxygen. Thioploca ingrica populations were exclusively found close to river outlets in a bioturbated sediment with separate sulphidic spots and worm burrow walls containing nitrate and oxygen. It is hypothesized that the subsurface T. ingrica have a special advantage in this heterogeneous environment using their sheath surrounding the bacterial trichomes when navigating between electron donor and acceptor.
authors.affiliation: Department of Biological Sciences, Aarhus University, Ny Munkegade 114, Aarhus C, Denmark.
authors.forename: Signe
authors.initials: S
authors.lastname: Høgslund
authors.forename: Jeppe Lund
authors.initials: JL
authors.lastname: Nielsen
authors.forename: Lars Peter
authors.initials: LP
authors.lastname: Nielsen
mesh_terms: D018533:Biomass; D004269:DNA, Bacterial / Q000235:genetics; D003718:Denmark; D005618:Fresh Water / Q000382:microbiology; D019015:Geologic Sediments / Q000382:microbiology*; D009566:Nitrates / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D041962:Thiotrichaceae / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D009566:Nitrates; D010710:Phosphates; D012336:RNA, Ribosomal, 16S