Deep biosphere-related bacteria within the subsurface of tidal flat sediments.
Biogeochemical and microbiological processes in the upper sediment layers of tidal flats were analysed in many investigations, while deeper zones remained largely unexplored. Therefore, denaturant gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments along the depth profile of up to 5.5 m-long sediment cores was performed in comparison with lithological and geochemical parameters. The investigation revealed that different compartments of the sediment columns were characterized by specific microbial communities. These compartments were analysed by sequencing of 113 DGGE bands. The upper layers down to 160-200 cm were dominated by gamma- and delta-Proteobacteria representing more than 60% of the total number of phylotypes. Underneath, a striking shift in community composition was observed, as the Proteobacteria were replaced by Chloroflexi with more than 60% of all sequences. As sulfate was still available as an electron acceptor in these layers, the abundance of Chloroflexi might be promoted by the electron donor or the quality of the carbon source. The dominance of this group, previously known as green non-sulfur bacteria, indicates the presence of a typical deep-biosphere microbial community in relatively young subsurface sediments. Thus, tidal flats might offer a convenient possibility to study and understand certain aspects of the deep biosphere in general.
Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Carl-von-Ossietzky Strasse, 9-11, D-26129 Oldenburg, Germany.
Reinhard
R
Wilms
Beate
B
Köpke
Henrik
H
Sass
Tae Soo
TS
Chang
Heribert
H
Cypionka
Bert
B
Engelen
D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development*; D004269:DNA, Bacterial / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D019015:Geologic Sediments / Q000382:microbiology*; D010802:Phylogeny; D012329:RNA, Bacterial / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012623:Seawater / Q000382:microbiology; D014871:Water Microbiology
D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S