An immunochemical in situ approach to detect adaptation processes in the photosynthetic apparatus of diatoms of the Wadden Sea sediment surface layers.

Intertidal Wadden Sea sediment surface layers located near the North Sea shore at Dangast (Germany) were subjected to quantitative chlorophyll and protein extractions followed by SDS-PAGE and Western immunoblotting. During the study, benthic diatoms were almost exclusively the only group of microphytobenthos in this area performing oxygenic photosynthesis. Three successive extractions with 90% acetone yielded more than 98% of the extractable pigments. The absorption spectra of the extracts of sediment samples were nearly identical to those obtained from the diatom Phaeodactylum tricornutum. Ten repetitive extractions with SDS containing loading buffer used for SDS-PAGE ensured that more than 98% of the extractable protein was recovered. Subsequent Western immunoblotting with an antiserum directed against the subunits of the main light harvesting complex of the diatom Cyclotella cryptica showed that the antiserum immunodecorated selectively subunits of diatomaceous light harvesting complexes. This finding demonstrated that a taxon specific class of polypeptides could be visualized and quantified directly in sediment samples. In shading experiments, shaded sedimient areas generally revealed higher amounts of light harvesting subunits which could be immunodecorized. The improved mnethodological approach and the results are discussed in the context of the current development of direct molecular methods for the investigation of activities and adaptation processes of specific groups of microorganisms in their natural habitats.