Species and Fatty Acid Diversity of Desmodesmus (Chlorophyta) in a Local Japanese Area and Identification of New Docosahexaenoic Acid-Producing Species

Abstract

Desmodesmus is a green microalgal genus that is frequently found in aquatic environments. Its high biomass productivity and potential as a source of lipids have attracted considerable attention. Although Desmodesmus is ubiquitous, it is difficult to identify; even within a small area, the diversity of the species and the fatty acids they produce are unknown. In this study, we performed scanning electron microscopy (SEM) and analyzed the genetic diversity of the internal transcribed spacer (ITS) region to accurately identify Desmodesmus in a local area of Japan (Saga City, Saga Pref.) and to assess its existence as a biological resource. In addition, we analyzed the fatty acid composition and content of the newly established strains. In total, 10 new strains were established, and 9 previously described species were identified. The presence of a cosmopolitan species indicated the global distribution of Desmodesmus. However, only regional species were found. One strain, dSgDes-b, did not form a clear clade with any described species in the phylogenetic analysis and had a characteristic ITS2 secondary structure. The cell wall of this strain exhibited a distinctive microstructure, and it produced docosahexaenoic acid (DHA); hence, the strain was described as a new species, Desmodesmus dohacommunis Demura sp. nov. Thus, useful information regarding the use of Desmodesmus as a bioresource was provided.