Diplosphaera elongata sp. nova: Morphology and Phenotypic Plasticity of This New Microalga Isolated from Lichen Thalli

Abstract

Lichen phycobiomes have recently emerged as a source of biodiversity and new species of microalgae. Although in the genus Diplosphaera free-living microalgae are common, numerous strains belonging to this genus have frequently been recognized or isolated from lichen thalli. In this study, a comprehensive analysis of the strain Diplosphaera sp. ASUV135, isolated from a lichen thallus, has been carried out using an integrative taxonomic approach. The SSU and nuclear-encoding ITS rDNA, as well as the chloroplast rbcL gene, were sequenced and analyzed to ascertain its taxonomic position and phylogenetic relationships within the genus Diplosphaera. This strain was also analyzed by light, confocal and transmission microscopy for morphological and ultrastructural characterization. The phenotypic plasticity in this strain was also confirmed by changes in its morphology under different growth conditions, as well as those of modulated Chlorophyll a fluorescence emissions, to understand its photosynthetic functioning. Our results pointed out that this strain represents a new taxon within the genus Diplosphaera (Prasiola group), described here as Diplosphaera elongate sp. nova. This study also provides tools for future research on organisms with high phenotypic plasticity by using molecular, morphological, ultrastructural and physiological approaches.