Cyanobacteria and Protists

As primary producers Cyanobacteria are often engaged in close physical and physiological interactions with heterotrophic microorganisms in nature, like bacteria, fungi and protozoa (Fig. 2). For laboratory investigations, it is accordingly difficult to obtain pure, axenic cyanobacterial cultures. Most cyanobacterial strains in our collection are thus non-axenic (98%). For a comprehensive characterisation and phylogenetic classification of cyanobacterial strains and to explore the biological diversity of heterotrophs in non-axenic cyanobacterial cultures, a pilot project has been initiated: the microbiomes present in mixed cultures of Planktothrix, Phormidium, and Oculatella strains were analysed by metagenomic sequencing using the PacBio Sequel IIe technology available at the DSMZ. The complete genome sequence of the corresponding cyanobacterium was obtained in a single run from each of the cultures. In addition, up to five genomes of accompanying bacteria occurring in the cyanosphere were completely deciphered per cyanobacterial culture. The genome sequences of the cyanobacteria were analysed bioinformatically, resulting in the genome-based taxonomic assessment of the strains, the determination of their toxigenic potential and the elucidation of their axenity status. With the further implementation of this approach, Cyanobacteria of the DSMZ collection will contribute to an improvement of the cyanobacterial phylogeny and taxonomy. Furthermore, the DSMZ will provide the scientific community and their industrial partners with in-depth characterized cyanobacterial cultures.