Morphology and molecular characterization of a new Chloroidium (Trebouxiophyceae, Chlorophyta) species isolated from lichen in Antarctica

Abstract

Antarctica's harsh environment supports a unique diversity of microalgae that inhabit freshwater, soil and snow, and engage in symbiotic associations with lichens. Among these, the photosynthetic eukaryotic algae in lichens primarily exhibit Chlorella-like morphology, which complicates their identification as a result of the simplicity of their form. In the present study, we aimed to identify a Chlorella-like strain isolated from the lichen Psoroma antarcticum in Antarctica based on its morphological and molecular characteristics. The strain PAMC 29142 showed ellipsoidal to almost spherical cells with parietal chloroplasts and reproduced through equally sized autospores, closely resembling other members of the genus Chloroidium. The phylogenetic analyses using nuclear small subunit and internal transcribed spacer rDNA sequences data confirmed that PAMC 29142 represents a distinct lineage within the genus. Internal transcribed spacer 2 secondary structures and the compensatory base changes approach were used to compare this strain with other Chloroidium species. Based on comprehensive morphological and molecular data, we propose the designation of PAMC 29142 as a new species, Chloroidium psoromicola sp. nov.