Global ubiquity and local endemism of free-living terrestrial protists: phylogeographic assessment of the streptophyte alga Klebsormidium.

Despite considerable research attention during the last 10 years, the distribution and biogeography of protists remain as highly controversial issues. The presumably huge population sizes and unlimited dispersal capabilities should result in protist ubiquity. However, recent molecular investigations suggest that protist communities exhibit strong biogeographic patterns. Here, we examined the biogeographic pattern of a very common green algal genus Klebsormidium. We evaluated the geographic distribution of rbcL genotypes for 190 isolates sampled in six sampling regions located in Europe, North America and Asia. Measures of correlation between genetic and geographic distance matrices revealed a differential distribution pattern on two geographic levels. Globally, the populations were genetically homogeneous; locally, the genotypes were patchily distributed. We hypothesized that a local fine-scale structuring of genotypes may be caused by various ecological factors, in particular, by the habitat differentiation of particular genotypes. Our investigations also identified a large number of new, previously unrecognized lineages. A total of 44 genotypes were identified and more than 66% of these were reported for the first time.

Morphological and molecular characterization within 26 strains of the genus Cylindrospermum (Nostocaceae, Cyanobacteria), with descriptions of three new species.

Twenty-six strains morphologically identified as Cylindrospermum as well as the closely related taxon Cronbergia siamensis were examined microscopically as well as phylogenetically using sequence data for the 16S rRNA gene and the 16S-23S internal transcribed spacer (ITS) region. Phylogenetic analysis of the 16S rRNA revealed three distinct clades. The clade we designate as Cylindrospermum sensu stricto contained all five of the foundational species, C. maius, C. stagnale, C. licheniforme, C. muscicola, and C. catenatum. In addition to these taxa, three species new to science in this clade were described: C. badium, C. moravicum, and C. pellucidum. Our evidence indicated that Cronbergia is a later synonym of Cylindrospermum. The phylogenetic position of Cylindrospermum within the Nostocaceae was not clearly resolved in our analyses. Cylindrospermum is unusual among cyanobacterial genera in that the morphological diversity appears to be more evident than sequence divergence. Taxa were clearly separable using morphology, but had very high percent similarity among ribosomal sequences. Given the high diversity we noted in this study, we conclude that there is likely much more diversity remaining to be described in this genus.

Completion of cell division is associated with maximum telomerase activity in naturally synchronized cultures of the green alga Desmodesmus quadricauda.

Telomerase maintains the ends of eukaryotic chromosomes, and its activity is an important parameter correlating with the proliferative capacity of cells. We have investigated cell cycle-specific changes in telomerase activity using cultures of Desmodesmus quadricauda, a model alga naturally synchronized by light/dark entrainment. A quantitative telomerase assay revealed high activity in algal cultures, with slight changes during the light period. Significantly increased telomerase activity was observed at the end of the dark phase, when cell division was complete. In contrast to other models, a natural separation between nuclear and cellular division typical for the cell cycle in D. quadricauda made this observation possible.