Molecular Biological and Physiological Investigations of Heterotrophic Bacteria Associated with Marine Filamentous Cyanobacteria

The composition of the heterotrophic community within the cultures of the cyanobacteria Oscillatoria brevis and Nodularia harveyana was investigated. 51 heterotrophic strains were isolated, of which 4 were chosen for further investigations: a red, a pink, and a colourless one, grouping with Porphyrobacter, Roseobacter, and Rhodobacter respectively, and a yellow one grouping with Muricauda. For further investigations specific FISH probes were designed for Muricauda and for the Erythrobacteraceae. Axenic cultures of Nodularia and Oscillatoria were prepared, which then were mixed with single pure cultures of the four heterotrophs. A detrimental effect was determined only for Oscillatoria. It could be shown that in all cases new heterotrophic communities developed in the cultures. The occurrence of the heterotrophs was studied with ten further cyanobacterial cultures. Furthermore, the heterotrophs were characterised concerning their morphological, biochemical, and physiological properties.