Out of Antarctica: new insights into Antarctic Subcluster 5.2 picocyanobacteria based on high-quality genomes
Benoit Durieu, Valentina Savaglia, Mick Van Vlierberghe, Valérian Lupo, Denis Baurain, Annick Wilmotte, Luc Cornet
Synechococcus-like cyanobacteria are cosmopolitan unicellular picocyanobacteria that have colonized diverse aquatic and terrestrial habitats. The so-called ‘subcluster 5.2’ represents a particularly diversified subgroup, including marine and freshwater organisms adapted to extreme conditions, notably polar environments. We increased the genomic representation of polar taxa in this subcluster by reconstructing new high-quality genomes from five Antarctic lacustrine strains and one Arctic freshwater isolate using a combination of small Illumina and long Nanopore reads. A maximum likelihood (ML) phylogenomic analysis of these new assemblies combined with all publicly available good quality assemblies of the subcluster 5.2 suggests evidence of a dispersal process from Antarctica. Indeed, the topology of the phylogenomic tree indicates one basal Antarctic lineage followed by the emergence of two lineages, one Antarctic and one non-Antarctic (Spain). This finding is further supported by a 16S rRNA ML phylogenetic and a pangenomic analysis. Although secondary colonization of Antarctica by cyanobacteria following the cooling of the continent 34 million years ago has been reported, this study is the first to support an ‘Out-of-Antarctica’ scenario inside subcluster 5.2.
https://doi.org/10.64898/2025.12.17.694815