Pleurastrosarcina terriformae, a new species of a rare desert trebouxiophycean alga discovered by an integrative approach

Biological soil crusts of extreme habitats (semi-deserts and deserts) are dominated by cyanobacteria and microalgae. The most abundant taxa are green algae belonging to the classes Chlorophyceae and Trebouxiophyceae. Specimens with sarcinoid-like morphology (cells arranged in packages) represent one group of these microalgae. The genus Pleurastrosarcina consists of two species, which were originally described as Chlorosarcina (P. brevispinosa and P. longispinosa). Both species are exclusively found from arid soils. However, these species were only reported few times and probably overlooked especially if no akinetes were present. During studying soil samples collected from different regions of the Atacama desert (Chile), we isolated two strains, which were morphologically similar to both Pleurastrosarcina species. The phylogenetic analyses confirmed that they belong to this genus. The ITS-2/CBC approach revealed that both new isolates represent a new species, P. terriformae. The comparison with other available strains demonstrated that this new species is not restricted to South America and was also found in coastal area in Europe. The six investigated strains showed a high phenotypic plasticity, which is reflected in the descriptions of several varieties.