NO3– nutrition and salt tolerance in the cyanobacterium Anabaena sp. PCC 7120 and mutant strains

Growth of the cyanobacterium Anabaena sp. PCC 7120 and its nitrate assimilation-defective mutants was inversely proportional to the NaCl concentration in the medium. Presence of nitrate in the saline medium protected the growth of the parent but not of the mutant strains from salt toxicity. On the other hand, ammonium nitrogen protected the growth of all the strains from salt toxicity. However, the effect was less than that of nitrate. An altered sodium transport system was evident in the mutant strains and was most marked in mutant SP9. The cellular sodium concentration in parent and mutant strains also varied. Although mutant SP9 exhibited the lowest level of cellular sodium, it was as sensitive to salt toxicity as other strains. It is assumed that merely the presence of a toxic level of NaCl in the ambient environment is sufficient to damage the structural and functional components of the plasma membrane.     

Learning to swim in a sea of genomic data

A report on the 63rd American Society of Human Genetics (ASHG) meeting held in Boston, USA, 22–26 October 2013.     

The measurement of primary productivity in a high-rate oxidation pond (HROP)

A high-rate oxidation pond is studied as a model system forcomparing ¹⁴C and oxygen evolution methods as tools for measuringprimary productivity in hypertrophic aquatic systems. Our resultsindicate that at very dense algal populations (up to 5 mg chl.a l^–1) and high photosynthetic rates, ¹⁴C based resultsmay severely underestimate primary productivity, unless a wayis found to keep incubation times very short. Results obtainedwith our oxygen electrode were almost an order of magnitudehigher than those obtained by all ¹⁴C procedures. These highervalues correspond fairly well with a field-tested computer-simulationmodel, as well as with direct harvest data obtained at the samepond when operated under similar conditions. The examinationof the size-fractionation of the photosynthetic activity underscoredthe important contribution of nannoplanktonic algae to the totalproduction of the system. ^*This paper is the result of a study made at the Group for AquaticPrimary Productivity (GAP), Second International Workshop heldat the Technion-Israel Institute of Technology in Haifa in May1984     

Fast Charge-Transfer Rates in Li-CO2 Batteries with a Coupled Cation-Electron Transfer Process

Li-CO₂ batteries with a high theoretical energy density (1876 Wh kg⁻¹) have unique benefits for reversible carbon fixation for energy storage systems. However, due to lack of stable and highly active catalysts, the long-term operation of Li-CO₂ batteries is limited to low current densities (mainly <0.2 mA cm⁻²) that are far from practical conditions. In this work, it is discovered that, with an ionic liquid-based electrolyte, highly active and stable transition metal trichalcogenide alloy catalysts of Sb_0.67Bi_1.33X₃ (X = S, Te) enable operation of the Li-CO₂ battery at a very high current rate of 1 mA cm⁻² for up to 220 cycles. It is revealed that: i) the type of chalcogenide (Te vs S) significantly affects the electronic and catalytic properties of the catalysts, ii) a coupled cation-electron charge transfer process facilitates the carbon dioxide reduction reaction (CO₂RR) occurring during discharge, and iii) the concentration of ionic liquid in the electrolyte controls the number of participating CO₂ molecules in reactions. A combination of these key factors is found to be crucial for a successful operation of the Li-CO₂ chemistry at high current rates. This work introduces a new class of catalysts with potential to fundamentally solve challenges of this type of batteries.     

Differential stomatal closure by abscisic acid in epidermal strips of green and pigmented leaves or leaf parts

Response of stomata in epidermal strips from green leaves ofTradescantia sillamontana and anthocyanin-rich purple leaves ofT. virginiana and from green and pigmented regions ofPedilanthus tithymaloides leaves, to ABA have been compared. Stomata from anthocyanin-rich leaves or leaf parts appeared to be relatively insensitive to ABA as compared to those from green leaves or leaf parts. Observations indicate the possibility of the involvement of endogenous anthocyanins in antagonising ABA in preventing the stomatal opening.