Phylogenetic characterization and morphological and physiological aspects of a novel acidotolerant and halotolerant microalga Coccomyxa onubensis sp. nov. (Chlorophyta,Trebouxiophyceae)

The genus Coccomyxa comprises green microalgae, which can be found worldwide in remarkably versatile aquatic and terrestrial ecosystems including symbiotic associations with a number of different hosts. In this study, we describe a new species, Coccomyxa onubensis, based on 18S and ITS ribosomal DNA (rDNA) sequence data. Coccomyxa onubensis was isolated from acidic water, and its ability to adapt to a wide range of acidic and alkaline pH values and to high salinity was analyzed. The long-term adaptation capacity of the microalga to such extreme conditions was evaluated by performing continuous repeated batches at selected salt concentrations and pH values. Adapted cultures of C. onubensis were found to yield high biomass productivities from pH 2.5 to 9, with maximum yields at acidic pH between 2.5 and 4.5. Moreover, C. onubensis was also found to adapt to salinities as high as 0.5 M NaCl, reaching biomass productivities that were similar to those of control cultures. Ultrastructural analysis by transmission electron microscopy of C. onubensis cells adapted to high salinity showed a robust response to hyperosmotic shock. Thus, C. onubensis was found to be acidotolerant and halotolerant. High biomass productivity over a wide range of pH and salinities denotes C. onubensis as an interesting candidate for various biotechnological applications including outdoor biomass production.