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Thylakoid and cytoplasmic membranes of the cyanobacterium Syncchocystis sp. PCC 6803 were purified by sucrose gradient centrifugation. Both membranes oxidize NADH in a rotenone-sensitive reaction. Antibodies prepared against psbG/ndhKand ndhJ fusion proteins detect the corresponding polypeptides in both membrane preparations. This demonstrates that a NADH-dehydrogenase, homologous to the mitochondrial NADHubiquinone-oxidoreductase (complex I of the respiratory chain) is present in cyanobacteria, The NADH-dehydrogenase can be solubilized with the detergent /-D-dodecylmaltoside. Sedimentation analysis of the solubilized enzyme on a sucrose gradient indicates that it is a multisubunit protein complex.
An antibody against the NDH-K subunit of the NAD(P)H-dehydrogenase from the cyanobacterium Synechocystis sp. PCC6803 was used to isolate a subcomplex ofthe enzyme from Triton X-lOO solubilized total membranes by immunoaffinity chromatography. The isolated subcomplex consisted of seven major polypeptides with molecular masses of 43, 27, 24, 21, 18, 14 and 7 kDa. The amino-terminal amino acid sequences of the polypeptides were determined. By comparing the sequences with the amino acid sequences deduced from DNA. three proteins were identified as NDH-H (43 kDa). NDH-K (27 kDa) and NDH-J (24 kDa). A fourth subunit (NDH-J, 21 kDa) was identified by Western blot analysis with an NDH-J antibody.
While beneficial sponge-microbe associations have received much attention in recent years, less effort has been undertaken to investigate the interactions of sponges with potentially pathogenic microorganisms. Thus, the aim of this study was to examine two selected Caribbean disease conditions, termed “Sponge Orange Band” and “Sponge White Patch”, via ecological and molecular methods. Sponge Orange Band (SOB) disease affects the prominent Caribbean barrel sponge Xestospongia muta that is counted among the high-microbial-abundance (HMA) sponges, whereas Sponge White Patch (SWP) disease affects the abundant rope sponge Amphimedon compressa that belongs to the low-microbial-abundance (LMA) sponges. I have documented for both Caribbean sponge diseases a disease progression going along with massive tissue destruction as well as loss of the characteristic microbial signatures. Even though new bacteria were shown to colonize the bleached areas, the infection trials revealed in both cases no indication for the involvement of a microbial pathogen as an etiologic agent of disease leaving us still in the dark about the cause of Sponge Orange Band as well as Sponge White Patch disease.