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 sh ore at Dangast (Germany) were subjected to quantitative chlorophyll and pro tein extractions followed by SDS-PAGE and Western immunoblotting. During th e study, benthic diatoms were almost exclusively the only group of microphy tobenthos in this area performing oxygenic photosynthesis. Three successive extractions with 90% acetone yielded more than 98% of the extractable pigm ents. The absorption spectra of the extracts of sediment samples were nearl y identical to those obtained from the diatom Phaeodactylum,tricornutum. Te n repetitive extractions with SDS containing loading buffer used for SDS-PA GE ensured that more than 98% of the extractable protein was recovered. Sub sequent Western immunoblotting with an antiserum directed against the subun its of the main light harvesting complex of the diatom Cyclotella cryptica showed that the antiserum immunodecorated selectively subunits of diatomace ous light harvesting complexes. This finding demonstrated that a taxon spec ific class of polypeptides could be visualized and quantified directly in s ediment samples. In shading experiments, shaded sediment areas generally re vealed higher amounts of light harvesting subunits which could be immunodec orized. The improved methodological approach and the results are discussed in the context of the current development of direct molecular methods for t he investigation of activities and adaptation processes of specific groups of microorganisms in their natural habitats. (C) 1999 Elsevier Science B.V. All rights reserved.