title: Phylogeny of Proteobacteria and Bacteroidetes from oxic habitats of a tidal flat ecosystem.
abstract: Bacteria of the phyla Proteobacteria and Bacteroidetes are known to be the most prominent heterotrophic organisms in marine surface waters. In order to investigate the occurrence of these phyla in a coastal environment, the tidal flat ecosystem German Wadden Sea, we analyzed a clone library of PCR-amplified and sequenced 16S rRNA gene fragments and isolated 46 new strains affiliated with these phyla from the water column with various polymers and complex media as substrates. The phylogenetic affiliation of these strains was analyzed on the basis of sequenced 16S rRNA gene fragments. Subsequently, a comprehensive phylogenetic analysis of Proteobacteria and Bacteroidetes including available sequences from oxic habitats of earlier studies of this ecosystem was performed. Sequences of the earlier studies were derived from isolation approaches and from denaturing gradient gel electrophoresis (DGGE) analyses of environmental samples and high dilution steps of MPN (most probable number) cultures. The majority of the 265 sequences included in this analysis affiliated with alpha-Proteobacteria (45.3%), gamma-Proteobacteria (31.7%), and Bacteroidetes (16.2%). Almost 7% belong to the delta-Proteobacteria and several of these clones affiliated with the Myxococcales, a group comprising obligate aerobic organisms. Within the alpha- and gamma-Proteobacteria specific clusters were identified including isolates from high dilution steps of dilution cultures and/or clones from the clone library or DGGE gels, implying a high abundance of some of these organisms. Within the gamma-Proteobacteria a new cluster is proposed, which consists of marine surface-attached organisms. This SAMMIC (Surface Attached Marine MICrobes) cluster comprises only uncultured phylotypes and exhibits a global distribution. Overall, the analysis indicates that Proteobacteria and Bacteroidetes of the Wadden Sea have a surprisingly high diversity, presumably a result of the signature of this ecosystem as a melting pot at the land-sea interface and comprising a great habitat variety.
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment ICBM, University of Oldenburg, P.O. Box 2503, D-26111 Oldenburg, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Stevens
authors.forename: Matthias
authors.initials: M
authors.lastname: Stübner
authors.forename: Meinhard
authors.initials: M
authors.lastname: Simon
authors.forename: Thorsten
authors.initials: T
authors.lastname: Brinkhoff
mesh_terms: D041963:Bacteroidetes / Q000235:genetics*; D001483:Base Sequence; D017753:Ecosystem; D015723:Gene Library; D005858:Germany; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D020560:Proteobacteria / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D014871:Water Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S