Research

A. Gittel, Y. C. Hilker, B. Engelen, H. Cypionka, H. Sass

Detecting sulfate-reducing bacteria in coastal subsurface sediments by means of geochemical and molecular approaches

Sulfate-reducing bacteria (SRB) are responsible for essential steps of the anaerobic degradation of organic matter in marine sediments. To investigate ecological adaptations and physiological capacities pure cultures are crucial. However, the in situ most abundant types of SRB escaped isolation so far. Thus, the aim of the present study was to improve the enrichment and isolation of SRB using a combined geochemical and molecular approach. This method was applied to samples from a sediment core of six meter length taken on a North Sea tidal flat (Germany). The geochemical data comprised sulfate reduction rates (35S-sulfate) as well as porewater profiles of sulfate and acetate (IC, HPLC). These data were compared to a vertical profile of the gene encoding the key enzyme of dissimilatory sulfate reduction (dsrAB) obtained by quantitative polymerase chain reaction (qPCR). Enrichment experiments from the identified most active layers were started following a novel approach: Successional changes of the species composition were monitored by DGGE and CARD-FISH in order to detect and isolate the dominant types of SRB at the time of their maximum development. In this way, promising horizons for the isolation of pure cultures of SRB were offered.