“This review covers essentially all aspects of the organisms in the green algal family Volvocaceae and suggests the genetic history of the various steps in their evolution from their unicellular ancestors. “
“The availability and composition of dissolved nitrogen in ocean waters are factors that influence species composition in natural phytoplankton communities. The same factors affect the ratio of organic to inorganic carbon incorporation Panobinostat supplier in calcifying species, such as the coccolithophore Emiliania huxleyi (Lohman) W. W.
Hay et H. Mohler. E. huxleyi has been shown to thrive on various nitrogen sources, including dissolved organic nitrogen. Nevertheless, assimilation of dissolved nitrogen under nitrogen-replete and -limited conditions is not well understood in this ecologically important species. In this study, the complete amino acid sequences for three functional genes involved in nitrogen metabolism in E. huxleyi were identified: a putative formamidase, a glutamine synthetase (GSII family), and assimilatory BMN 673 in vivo nitrate reductase. Expression patterns of the three
enzymes in cells grown on inorganic as well as organic nitrogen sources indicated reduced expression levels of nitrate reductase when cells were grown on NH4+ and a reduced expression level of the putative formamidase when growth was on NO3−. The data DOK2 reported here suggest the presence of a nitrogen preference hierarchy in E. huxleyi. In addition, the gene encoding for a phosphate repressible phosphate permease was more highly expressed in cells growing on formamide than in cells growing on inorganic nitrogen sources. This finding suggests a coupling between phosphate and nitrogen metabolism, which might give this species a competitive advantage in nutrient-depleted environments. The potential of using expression of genes investigated
here as indicators of specific nitrogen-metabolism strategies of E. huxleyi in natural populations of phytoplankton is discussed. “
“A high degree of pseudo-cryptic diversity was reported in the well-studied diatom genus Pseudo-nitzschia. Studies off the coast of Washington State revealed the presence of hitherto undescribed diversity of Pseudo-nitzschia. Forty-one clonal strains, representing six different taxa of the P. pseudodelicatissima complex, were studied morphologically using LM and EM, and genetically using genes from three different cellular compartments: the nucleus (D1–D3 of the LSU of rDNA and internal transcribed spacers [ITSs] of rDNA), the mitochondria (cytochrome c oxidase 1), and the plastids (LSU of RUBISCO). Strains in culture at the same time were used in mating studies to study reproductive isolation of species, and selected strains were examined for the production of the neurotoxin domoic acid (DA).