Abstract :
[en] Cyanobacteria are a phylum of photosynthetic bacteria that played an important role in the evolution of the planet by oxygenating its early atmosphere and provoking the Great Oxydation Event around 2.3 billion years ago. Early cyanobacteria were the ancestors of plastids and thus, at the origin of the highly successful algae and plants. Nowadays, they still are the basis of the food chain in many biotopes, as long as there is liquid water, light, air and some minerals. Some cyanobacterial taxa are very resistant to harsh environmental conditions, and thus, grow in polar, hypersaline, alkaline and/or arid biotopes, but also in spatial conditions. Furthermore, they are also a prolific source of secondary compounds with bioactivies. The BCCM/ULC public collection funded by the Belgian Science Policy Office since 2011 presently includes 224 cyanobacterial strains, with 140 being of Antarctic origin (catalogue: http://bccm.belspo.be/catalogues/ulc-catalogue-search). The strains are unicyanobacterial but not axenic, due to the well known difficulties of purifying them. Morphological identification showed that the strains belong to the orders of Synechococcales, Oscillatoriales, Pleurocapsales, Chroococcidiopsidales and Nostocales. Furthermore, 16S rRNA and ITS sequences of the strains are being characterized. Recent sequencing efforts increased the amount of available 16S rRNA sequences of BCCM/ULC strains to 190. Those sequences belong to 75 OTUs (groups of sequences with > 99 % 16S rRNA similarity), which represents a quite large diversity. To better characterize the microbiome of the cultures, a metagenomic analysis was performed for 12 polar or subpolar strains and three temperate ones, including three early-branching organisms that will be useful for phylogenomics. The design of a specific metagenomic pipeline enabled the easy recovery of the cyanobacterial genomes from the non-axenic cultures. In parallel, 31 genomes of co-cultivated bacteria (12 nearly complete) from the same cultures were determined. They mostly belonged to Bacteroidetes and Proteobacteria, some of them being very closely related, in spite of sometimes geographically distant sampling sites (Cornet et al. 2018). In summary, the BCCM/ULC public collection serves as a Biological Resource Centre to conserve ex situ and document the biodiversity of cyanobacteria and their microbiomes, as well as a repository for discovery of novel bioactive compounds.
Cornet, L., Bertrand, A., Hanikenne, M., Javaux, E., Wilmotte, A., & Baurain, D. (2018). Metagenomic assembly of new (sub)polar Cyanobacteria and their associated microbiome from non-axenic cultures. Microbial Genomics.4. DOI 10.1099/mgen.0.000212.
