BACTERIA IN THE MARINE SPONGE PACHYMATISMA JOHNSTONIA: STABLE ASSOCIATION OR TEMPORARILY CHANGING BIOCOENOSIS?Antje Wichels1, Steffen Kuppardt2, Gunnar Gerdts11Alfred Wegener Institute Foundation for Polar and Marine Research, Marine Station 2Helgoland, Dept. Ecological Chemistry, 27498 Helgoland, GermanyUniversity of Rostock, FB Biowissenschaften, 18051 Rostock, GermanyThe marine sponge Pachymatisma johnstonia (Demospongia) is a massive and compact sponge which grows in temperate and cold waters (North Sea, Northern Atlantic). The surface of Pachymatisma is plain and leathery, of grayish color and always without epibionts. The sponge is known to produce a potent bioactive glycoprotein (Pachymatismin) which inhibits cancer cells and has anti-leishmanial activity. The source of this protein, either sponges-born or produced by associated bacteria, still needs to be resolved. Since most of the marine bacteria are not culturable until now, we started to identify the bacteria associated with Pachymatisma using culture independent methods. Specimens, collected at different locations around the Orkney Isles (North Scotland) were analyzed regarding their associated bacteria directly after sampling and after 1 year of cultivation in a flow-through sea water aquarium on Helgoland. Molecular fingerprinting techniques (RISA and DGGE) were used to estimate the diversity of the bacteria associated with sponges of different origin. Similar band patterns in specimens of different locations were found but after 1 year of cultivation a shift in community composition was observed. Clonal databases of these samples also display a shift of the bacterial community composition. In their natural habitat, amongst other groups the majority of the clones belong to the Acidobacteria. After 1 year of cultivation the main groups were a Proteobacteria and Actinobacteria, no Acidobacteria were found. Consistently in both samples bacteria of the a Proteobacteria and Chloroflexi group were found. These two groups are presumed to live in close association with Pachymatisma johnstonia.