Physiological, Biochemical, and Molecular Characters for the Taxonomy of the Subgenera of Scenedesmus (Chlorococcales, Chlorophyta)

Abstract

Biochemical and physiological properties of 16 Scenedesmus species representing the three subgenera Scenedesmus. Acutodesmus. and Desmodesmus are not suitable for species differentiation. All Scenedesmus species studied thus far produce secondary carotenoids, e.g. astaxanthin and canthaxanthin, under nitrogen-deficient conditions. In addition, with the exception of one strain, hydrogenase activity under anaerobic conditions is generally present. Sequence analyses of ribosomal 185 RNAs indicate that the subgenus Desmodesmus is phylogenetically well separated from the other subgenera, whereas the separation of Scenedesmus and Acutodesmus appears less convincing and is dismissed in favour of a single subgenus, Scenedesmus. Three taxa formerly assigned to the genus Chlorella are shown to be unicellular species of the genus Scenedesmus. "Chlorella" fusca var. vacuolata and "C." fusca var. rubescens. which is closely related to 5. obliquus. belong to the Scenedesmus/Acutodesmus group. "C." fusca var. fusca is closely related to 5. communis and thus belongs to the subgenus Desmodesmus. Inclusion of Kermatia pupukensis into the genus Scenedesmus is also strongly supported by the RNA data which furthermore indicate a relationship with the subgenus Desmodesmus.

Characterization of marine microalga, Scenedesmus sp. strain JPCC GA0024 toward biofuel production

“…Especially, S. rubescens (formerly Chlorella fusca var. rubescens) (Kessler et al 1997) shows salt (NaCl) tolerance up to 3% NaCl (Huss et al 1999), but is not halophile. On the other hand, strain JPCC GA0024 was expected to have a halophilic behavior because the seawater requirement for efficient growth and lipid accumulation was observed (Fig.…”

Phenotypic plasticity in the green algae Desmodesmus and Scenedesmus with special reference to the induction of defensive morphology

“…Sequence analysis of the 18S-rDNA gene clearly supported the designation of just two subgenera, Desmodesmus and Scenedesmus. The existing separation in the two subgenera Acutodesmus and Scenedesmus (Hegewald 1978) was not supported by this analysis and combined into one subgenus Scenedesmus (Kessler et al 1997). Subsequent sequence analysis of the more variable internal transcribed spacer 2 (ITS-2) region was used to further clarify the taxonomy of Scenedesmus .…”

“…Kessler and co-workers using sequence analyses of 18S rDNA showed that two taxa of the unicellular Chlorella were in fact unicellular Scenedesmus while one Chlorella and one Kermatia had to be designated to Desmodesmus (Kessler et al 1997) ! A decade ago, an interesting dialogue took place between Trainor and Egan (1990) and Hegewald and Schmidt (1990) on Lagerheimia hindakii being the unicellular stage of D. subspicatus illustrative of the firmly anchored dogma of Desmodesmus and Scenedesmus being colonial.…”

“…They characterized the two groups as the non-spiny and the spiny group ). Attempts to reassess the taxonomy of Scenedesmus by biochemical and physiological properties failed and molecular techniques such as DNA/DNA hybridization and nucleotide sequence analysis were introduced to assist the reclassification of Scenedesmus (Kessler et al 1997). Sequence analysis of the 18S-rDNA gene clearly supported the designation of just two subgenera, Desmodesmus and Scenedesmus.…”

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“…For examp le, some researchers discussed the aforementioned characteristics in some cultured strains of D. communis (e.g., Ko marek & Ru zicka, 1969;Brezina, Hrib, & Ko marek, 1972;Steenbergen, 1978;Hegewald, 1989;Trainor, 1992;Bica et al, 2012). Kessler et al (1997) pointed out that the morphological characteristics and metabolic capacities are considered not only enough to clearly distinguish the different Scenedesmus and Desmodesmus taxa. Recently, the molecu lar phylogenetic analysis was imp lemented to solve some this taxonomic pu zzle (e.g., An, Friedl, & Hegewald, 1999;Van Hannen, Fin k, & Lurling, 2002;Hegewald & Wolf, 2003;Johnson, Fawley Vanormelingen et al, 2007;Fawley, M .W., Fawley, K.P.…”