Exploring diatom diversity through cultures - a case study from the Bow River, Canada

Diatom cultures can help answer taxonomic, biogeographic and ecological questions on a local and global scale. Unialgal cultures are derived from a single cell and provide abundant material for morphological and molecular analyses. The link between the historic morphological species concept and the molecular data is becoming increasingly important with the use of eDNA metabarcoding. Additionally, cultures provide insights into the life cycle of diatoms and thereby complement taxonomy and species ecology. In this study, we present an approach to extract benthic diatoms from an environmental sample to generate unialgal cultures. We explored diatom diversity in preserved assemblages and by culturing as many different taxa as possible from benthic freshwater samples taken on the same day from the Bow River in Calgary, Canada. With both methods we found a total of 221 different benthic diatom taxa, of which 182 were identified in the preserved diatom assemblages. Interestingly, an additional 39 taxa only appeared in the cultures. In total 129 strains were cultivated representing 71 different taxa. This study includes pictures of living cells demonstrating the additional merits of unialgal cultures, as they provide information on plastid details, auxospores and endosymbionts. Both, the identification of the diatom assemblages and the generation and identification of strains provide the foundation for additional water quality assessment tools, taxonomic insights and molecular references libraries

Murine Gamma-herpesvirus Immortalization of Fetal Liver-Derived B Cells Requires both the Viral Cyclin D Homolog and Latency-Associated Nuclear Antigen

Human gammaherpesviruses are associated with the development of lymphoproliferative diseases and B cell lymphomas, particularly in immunosuppressed hosts. Understanding the molecular mechanisms by which human gammaherpesviruses cause disease is hampered by the lack of convenient small animal models to study them. However, infection of laboratory strains of mice with the rodent virus murine gammaherpesvirus 68 (MHV68) has been useful in gaining insights into how gammaherpesviruses contribute to the genesis and progression of lymphoproliferative lesions. In this report we make the novel observation that MHV68 infection of murine day 15 fetal liver cells results in their immortalization and differentiation into B plasmablasts that can be propagated indefinitely in vitro, and can establish metastasizing lymphomas in mice lacking normal immune competence. The phenotype of the MHV68 immortalized B cell lines is similar to that observed in lymphomas caused by KSHV and resembles the favored phenotype observed during MHV68 infection in vivo. All established cell lines maintained the MHV68 genome, with limited viral gene expression and little or no detectable virus production - although virus reactivation could be induced upon crosslinking surface Ig. Notably, transcription of the genes encoding the MHV68 viral cyclin D homolog (v-cyclin) and the homolog of the KSHV latency-associated nuclear antigen (LANA), both of which are conserved among characterized γ2-herpesviruses, could consistently be detected in the established B cell lines. Furthermore, we show that the v-cyclin and LANA homologs are required for MHV68 immortalization of murine B cells. In contrast the M2 gene, which is unique to MHV68 and plays a role in latency and virus reactivation in vivo, was dispensable for B cell immortalization. This new model of gammaherpesvirus-driven B cell immortalization and differentiation in a small animal model establishes an experimental system for detailed investigation of the role of gammaherpesvirus gene products and host responses in the genesis and progression of gammaherpesvirus-associated lymphomas, and presents a convenient system to evaluate therapeutic modalities

Comparing limnological changes associated with 19th century canal construction and other catchment disturbances in four lakes within the Rideau Canal system, Ontario, Canada

Paleolimnological analysis of microfossils and physical sediment characteristics in 210Pb and Ambrosia dated sediment cores, along with diatom-inferred total phosphorus concentration [TP] reconstructions, were used to determine the trophic histories (ca 200 years) of four lakes within the Rideau Canal system, Ontario, Canada. Paleoecological information of the dominant diatom taxa that flourished during the pre-settlement period indicated that these lakes were naturally oligo-mesotrophic. At the estimated time of canal construction, all lakes demonstrated an increase in nutrients but their responses varied in magnitude. These differences were likely related to a number of variables, but the surface-area:watershed ratio appeared to be an important explanatory variable. Additionally, the similar trophic response of the control lake (not part of the canal), Otter Lake, illustrated the regional impact of past watershed disturbance (e.g. logging, settlement, mining, agriculture), not directly related to canal construction. In more recent years (~1970 to present), less productive planktonic species (e.g. Cyclotella comensis and Cyclotella aff. gordonensis) increased in all the study lakes. These recent water quality changes were attributed to improved nutrient retention of developing soils in secondary growth forests, the potential effects of climate warming, as well as mitigation efforts (e.g. decreased phosphorus concentrations in detergents, etc.). Eutrophication patterns determined for the deeper study lakes were similar to paleolimnological studies of other deep lakes in the canal system. However, the trophic response in the shallow lake, Lower Rideau Lake, is more pronounced at the time of canal construction than those of other shallow canal lake responses (e.g. nearby Lake Opinicon) and suggests that both alternative equilibrium states have occurred. This heightened response was attributed to increased nutrient export in Lower Rideau Lake’s limestone catchment and/or higher watershed disturbance. Finally, results from this study furthers our understanding of impacts in an integrated system of lakes and this information can be used to help set realistic mitigation targets for these and other lakes in the Rideau Canal system