Distribution and expression of the cyanate acquisition potential among cyanobacterial populations in oligotrophic marine waters

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 58 (2013): 1959-1971, doi:10.4319/lo.2013.58.6.1959.We assessed the significance of cyanate utilization in marine primary productivity from the distribution of a dedicated transporter (encoded by cynABD) in different ocean environments. Several lines of evidence indicate that the cyanate utilization potential is associated mainly with surface populations of Prochlorococcus. Spatial and temporal dimensions of cynA, cynS, and ntcA expression by picocyanobacteria in the northern Red Sea supported our previous finding that cynA transcripts accumulate under more stringent N-limiting conditions. At the same time, cyanate utilization appeared to be more complex than suggested in our earlier publication, as we showed that picocyanobacteria also express their cyanate utilization potential under conditions where labile organic N compounds, such as urea, accumulate. These include N-sufficient transient conditions that result from nutrient upwelling during early mixing events in autumn as well as during spring bloom conditions that follow deep mixing events. Our finding that cynA occurrence is common in diverse marine environments suggests that cyanate utilization may be of a more fundamental importance to picophytoplankton productivity than previously considered.Financial support for experimental work was provided by Israel Science Foundation grant 135/05; DNA sequencing, phylogenetic analyses, data processing, and manuscript preparation were supported by the National Science Foundation grant 1155566 in Chemical Oceanography

Characterization of cyanate metabolism in marine Synechococcus and Prochlorococcus spp.

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Applied and Environmental Microbiology 77 (2011): 291-301, doi:10.1128/AEM.01272-10.Cyanobacteria of the genera Synechococcus and Prochlorococcus are the most abundant photosynthetic organism on Earth occupying a key position at the base of marine food webs. The cynS gene that encodes cyanase was identified among bacterial, fungi and plant sequences in public databases and the gene was particularly prevalent among cyanobacteria, including numerous Prochlorococcus and Synechococcus strains. Phylogenetic analysis of cynS sequences retrieved from the Global Ocean Survey database identified >60% as belonging to unicellular marine cyanobacteria, suggesting an important role for cyanase in their nitrogen metabolism. Here we showed that marine cyanobacteria have a functionally active cyanase, the transcriptional regulation of which varies among strains and reflects the genomic context of cynS. In Prochlorococcus sp. MED4, cynS was presumably transcribed as part of the cynABDS operon, implying cyanase involvement in cyanate utilization. In Synechococcus sp. WH8102, expression was not related to nitrogen stress responses and here cyanase presumably serves in the detoxification of cyanate resulting from intracellular urea and/or carbamoyl phosphate decomposition. Lastly, we report on a cyanase activity encoded by cynH, a novel gene found in marine cyanobacteria only. The presence of dual cyanase genes in genomes of seven marine Synechococcus strains and their respective roles in nitrogen metabolism remain to be clarified.The Niedersachsen State Fund at the Hebrew University, the Israel Science Foundation (grant 135/05) and the NATO Science for Peace program (grant SfP 98216) all provided financial support

Maxwell's theory on a post-Riemannian spacetime and the equivalence principle

The form of Maxwell's theory is well known in the framework of general relativity, a fact that is related to the applicability of the principle of equivalence to electromagnetic phenomena. We pose the question whether this form changes if torsion and/or nonmetricity fields are allowed for in spacetime. Starting from the conservation laws of electric charge and magnetic flux, we recognize that the Maxwell equations themselves remain the same, but the constitutive law must depend on the metric and, additionally, may depend on quantities related to torsion and/or nonmetricity. We illustrate our results by putting an electric charge on top of a spherically symmetric exact solution of the metric-affine gauge theory of gravity (comprising torsion and nonmetricity). All this is compared to the recent results of Vandyck.Comment: 9 pages, REVTeX, no figures; minor changes, version to be published in Class. Quantum Gra

Predicting hydrologic response from physio-climatic attributes: an application to ungauged sub-catchments of the Burdekin River, North Queensland

The Burdekin is a large (140,000 square kilometres) catchment located in the dry tropics of North Queensland, Australia. To assess the water resources of this catchment, we require a methodology which will allow us to determine the daily streamflow at any point within the catchment. To this end, we have utilised a simple, lumped parameter model, IHACRES. Of the five parameters in the model, three have been set to default values, while the other two have been related to the physio-climatic attributes of the sub-catchment under consideration. The parameter defining total catchment water yield was constrained using %yield, which is related to summer precipitation, while the streamflow recession time constant was related to the total length of stream reaches in the catchment. These relationships were applicable over a range of scales from 68 square kilometres to 130,000 square kilometres, however three separate relationships were required to define c in the three major regions of the Burdekin – the upper Burdekin, Bowen, and Belyando Suttor. This research has provided a valuable insight into the hydrologic behaviour of the Burdekin catchment, while also providing a useful methodology for water resources assessment. The invariance of the relationships with scale indicates that the dominant processes may be similar for a range of scales, while the fact that different relationships were required for each of the three major regions indicates the geographic limitations of this regionalisation approach

Renal health after long-term exposure to tenofovir disoproxil fumarate (TDF) in HIV/HBV positive adults in Ghana

Objectives: The study assessed markers of renal health in HIV/HBV co-infected patients receiving TDF- containing antiretroviral therapy in Ghana. Methods: Urinary protein-to-creatinine ratio (uPCR) and albumin-to-protein ratio (uAPR) were measured cross-sectionally after a median of four years of TDF. At this time, alongside extensive laboratory testing, patients underwent evaluation of liver stiffness and blood pressure. The estimated glomerular filtration rate (eGFR) was measured longitudinally before and during TDF therapy. Results: Among 101 participants (66% women, median age 44 years, median CD4 count 572 cells/mm 3 ) 21% and 17% had detectable HIV-1 RNA and HBV DNA, respectively. Overall 35% showed hypertension, 6% diabetes, 7% liver stiffness indicative of cirrhosis, and 18% urinary excretion of Schistosoma antigen. Tubular proteinuria occurred in 16% of patients and was independently predicted by female gender and hypertension. The eGFR declined by median 1.8 ml/min/year during TDF exposure (IQR −4.4, −0.0); more pronounced declines ( ≥5 ml/min/year) occurred in 22% of patients and were associated with receiv-ing ritonavir-boosted lopinavir rather than efavirenz. HBV DNA, HBeAg, transaminases, and liver stiffness were not predictive of renal function abnormalities. Conclusions: The findings mandate improved diagnosis and management of hypertension and suggest targeted laboratory monitoring of patients receiving TDF alongside a booster in sub-Saharan Africa