Microbial diversity and activities within
the subsurface of tidal-flat sediments
Tidal flats are young and dynamic ecosystems showing intense microbial activities with a variety of metabolic processes occuring along the depth profile of the sediment column. To understand the function and composition of microbial communities within the sediment subsurface, we have used a combination of geochemical, microbiological and molecular biological techniques. This polyphasic approach was applied to sediment cores from different locations of a German tidal flat area from the sediment surface down to a depth of 5.5 m. The molecular biological investigation by DGGE analysis revealed that different compartments of the sediment columns were characterized by specific microbial communities. In total, 113 DGGE bands were sequenced. The upper sandy layers were dominated by various Proteobacteria. Below this zone, a dramatical shift with depth was observed. Here the Proteobacteria were replaced by the Chloroflexus group, a typical deep subsurface phylum. A slightly different shift was also detected by the cultivation approach. In total, 112 pure cultures were isolated, that could be grouped into 53 different operational taxonomical units (OTU). In the deeper mud-dominated sediment layers almost exclusively endospore-forming bacteria were detected. To link the information of who is there with geochemical profiles, the abundance of sulfate reducers and methanogens was determined by quantitative PCR. Additionally, exoenzyme activities and sulfate reduction rates were measured.
Köpke, Beate (2007) Dissertation: "Verteilung, Zusammensetzung und Aktivitäten mikrobieller Gemeinschaften in Wattsedimenten von der Oberfläche bis in mehrere Meter Tiefe"
Wilms, Reinhard (2006) Dissertation: "Molekularbiologische Erfassung und Charakterisierung der mikrobiellen Gemeinschaften im Rückseitenwatt der Insel Spiekeroog"
Köpke B, Wilms R, Engelen B, Cypionka H, Sass H (2005) Microbial diversity in coastal subsurface sediments - a cultivation approach using various electron acceptors and substrate gradients. Appl Environ Microbiol 71:7819-7830
Wilms R, Sass H, Köpke B, Cypionka H, Engelen B (2007) Methane and sulfate profiles within the subsurface of a tidal flat are reflected by the distribution of sulfate-reducing bacteria and methanogenic archaea. FEMS Microbiol Ecol 59:611621
Wilms R, Sass H, Köpke B, Köster J, Cypionka H, Engelen B (2006) Specific bacterial, archaeal, and eukaryotic communities in tidal-flat sediment along a vertical profile of several meters. Appl Environ Microbiol 72:2756-2764
Wilms R, Köpke B, Sass H, Chang TS, Cypionka H, Engelen B (2006) Deep biosphere-related bacteria within the subsurface of tidal flat sediments. Environ Microbiol 8:709-719