Snapshot prediction of carbon productivity,carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy

Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region''s phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a ‘snapshot'' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system.     

Statistical Mechanics of Zooplankton

Statistical mechanics provides the link between microscopic properties of many-particle systems and macroscopic properties such as pressure and temperature. Observations of similar “microscopic” quantities exist for the motion of zooplankton, as well as many species of other social animals. Herein, we propose to take average squared velocities as the definition of the “ecological temperature” of a population under different conditions on nutrients, light, oxygen and others. We test the usefulness of this definition on observations of the crustacean zooplankton Daphnia pulicaria. In one set of experiments, D. pulicaria is infested with the pathogen Vibrio cholerae, the causative agent of cholera. We find that infested D. pulicaria under light exposure have a significantly greater ecological temperature, which puts them at a greater risk of detection by visual predators. In a second set of experiments, we observe D. pulicaria in cold and warm water, and in darkness and under light exposure. Overall, our ecological temperature is a good discriminator of the crustacean’s swimming behavior.     

Apical Scaffolding Protein NHERF2 Modulates the Localization of Alternatively Spliced Plasma Membrane Ca2+ Pump 2B Variants in Polarized Epithelial Cells

The membrane localization of the plasma membrane Ca²⁺-ATPase isoform 2 (PMCA2) in polarized cells is determined by alternative splicing; the PMCA2w/b splice variant shows apical localization, whereas the PMCA2z/b and PMCA2x/b variants are mostly basolateral. We previously reported that PMCA2b interacts with the PDZ protein Na⁺/H⁺ exchanger regulatory factor 2 (NHERF2), but the role of this interaction for the specific membrane localization of PMCA2 is not known. Here we show that co-expression of NHERF2 greatly enhanced the apical localization of GFP-tagged PMCA2w/b in polarized Madin-Darby canine kidney cells. GFP-PMCA2z/b was also redirected to the apical membrane by NHERF2, whereas GFP-PMCA2x/b remained exclusively basolateral. In the presence of NHERF2, GFP-PMCA2w/b co-localized with the actin-binding protein ezrin even after disruption of the actin cytoskeleton by cytochalasin D or latrunculin B. Surface biotinylation and fluorescence recovery after photobleaching experiments demonstrated that NHERF2-mediated anchorage to the actin cytoskeleton reduced internalization and lateral mobility of the pump. Our results show that the specific interaction with NHERF2 enhances the apical concentration of PMCA2w/b by anchoring the pump to the apical membrane cytoskeleton. The data also suggest that the x/b splice form of PMCA2 contains a dominant lateral targeting signal, whereas the targeting and localization of the z/b form are more flexible and not fully determined by intrinsic sequence features.     

Zum Sauerstoffverbrauch von Myzus persicae (Sulz.) vor und nach Aufnahme des Blattrollvirus

Zusammenfassung Der Sauerstoffverbrauch virusfreier Myzus persicae (Sulz.) wird mit demjenigen blattrollvirusinfizierter Läuse verglichen. Der O₂-Verbrauch ist bei infizierten Tieren um rund 30% gegenüber virusfreien Kontrolltieren erniedrigt. Auf verschiedenen. Wirtspflanzen gehaltene Läuse zeigen keinen signifikanten Unterschied in ihrer Atmungsintensität. Die grö\te Erniedrigung des O₂-Bedarfs ist etwa 30 Stunden nach Ende des Infektionssaugens (d.h 38 Stunden nach Beginn der Nahrungsaufnahme) erreicht und steigt dann im Verlauf der folgenden 50 Stunden nicht weiter an. Der Stoffwechsel der Läuse wird offensichtlich durch die Aufnahme des Blattrollvirus gestört.

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Summary The intensity of respiration of virus-free aphids was compared with that of the same insects infected with potato leafroll virus. The former showed an average oxygen-consumption of 3.018 cm³/gm/hour, and the latter 1.992 cm³/gm/hour; which indicates a reduction of 33.9% in the oxygen-uptake in the infected animals. This reduction is associated with the infection and the multiplication of the virus in the insect. The oxygen-consumption was the same before the beginning and at the end of the infective suction period, falling afterwards over a period of 30 hours by about 30% of the first reading, and then remaining almost constant. This indicates a correlation between this variation in the oxygen-consumption and the multiplication of the virus in the aphid.

     

Time to Pregnancy: A Computational Method for Using the Duration of Non-Conception for Predicting Conception

An important problem in reproductive medicine is deciding when people who have failed to become pregnant without medical assistance should begin investigation and treatment. This study describes a computational approach to determining what can be deduced about a couple''s future chances of pregnancy from the number of menstrual cycles over which they have been trying to conceive. The starting point is that a couple''s fertility is inherently uncertain. This uncertainty is modelled as a probability distribution for the chance of conceiving in each menstrual cycle. We have developed a general numerical computational method, which uses Bayes'' theorem to generate a posterior distribution for a couple''s chance of conceiving in each cycle, conditional on the number of previous cycles of attempted conception. When various metrics of a couple''s expected chances of pregnancy were computed as a function of the number of cycles over which they had been trying to conceive, we found good fits to observed data on time to pregnancy for different populations. The commonly-used standard of 12 cycles of non-conception as an indicator of subfertility was found to be reasonably robust, though a larger or smaller number of cycles may be more appropriate depending on the population from which a couple is drawn and the precise subfertility metric which is most relevant, for example the probability of conception in the next cycle or the next 12 cycles. We have also applied our computational method to model the impact of female reproductive ageing. Results indicate that, for women over the age of 35, it may be appropriate to start investigation and treatment more quickly than for younger women. Ignoring reproductive decline during the period of attempted conception added up to two cycles to the computed number of cycles before reaching a metric of subfertility.