Effects of nitrogen sources on the nitrate assimilation in Haloferax mediterranei: growth kinetics and transcriptomic analysis

The haloarchaeon Haloferax mediterranei is able to grow in a defined culture media not only in the presence of inorganic nitrogen salt but also with amino acid as the sole nitrogen source. Assimilatory nitrate and nitrite reductases, respectively, catalyze the first and second reactions. The genes involved in this process are nasA, which encodes nitrate reductase and is found within the operon nasABC, and nasD, which encodes nitrite reductase. These genes are subjected to transcriptional regulation, being repressed in the presence of ammonium and induced with either nitrate or nitrite. This type of regulation has also been described when the amino acids are used as nitrogen source in the minimal media. Furthermore, it has been observed that the microorganism growth depends on nitrogen source, obtaining the lowest growth rate in the presence of nitrate and aspartate. In this paper, we present the results of a comparative study of microorganism growth and transcriptomic analysis of the operon nasABC and gene nasD in different nitrogen sources. The results are the first ever produced in relation to amino acids as nitrogen sources within the Halobacteriaceae family.

Nitrate reduction at Pt(1 0 0) single crystals and preferentially oriented nanoparticles in neutral media

The electroreduction of nitrate on Pt(1 0 0) electrodes in phosphate buffer neutral solution, pH 7.2, is reported. The sensitivity of the reaction to the crystallographic order of the surface is studied through the controlled introduction of defects by using stepped surfaces with (1 0 0) terraces of different length separated by monoatomic steps, either with (1 1 1) or (1 1 0) symmetry. The results of this study show that nitrate reduction occurs mainly on the well defined (1 0 0) terraces in the potential region where H adsorption starts to decrease, allowing the nitrate anion to access the surface. Adsorbed NO has been detected as a stable intermediate in this media. An oxidation process observed at 0.8 V has been identified as leading to the formation of adsorbed NO and being responsible for a secondary reduction process observed in the subsequent negative scan. Using in situ FTIRS, ammonium was found to be the main product of nitrate reduction. This species can be oxidized at high potentials resulting in adsorbed NO and nitrate (probably with nitrite as intermediate).

A methodology for evacuation route planning inside buildings using geospatial technology

Evacuation route planning is a fundamental task for building engineering projects. Safety regulations are established so that all occupants are driven on time out of a building to a secure place when faced with an emergency situation. As an example, Spanish building code requires the planning of evacuation routes on large and, usually, public buildings. Engineers often plan these routes on single building projects, repeatedly assigning clusters of rooms to each emergency exit in a trial-and-error process. But problems may arise for a building complex where distribution and use changes make visual analysis cumbersome and sometimes unfeasible. This problem could be solved by using well-known spatial analysis techniques, implemented as a specialized software able to partially emulate engineer reasoning. In this paper we propose and test an easily reproducible methodology that makes use of free and open source software components for solving a case study. We ran a complete test on a building floor at the University of Alicante (Spain). This institution offers a web service (WFS) that allows retrieval of 2D geometries from any building within its campus. We demonstrate how geospatial technologies and computational geometry algorithms can be used for automating the creation and optimization of evacuation routes. In our case study, the engineers’ task is to verify that the load capacity of each emergency exit does not exceed the standards specified by Spain’s current regulations. Using Dijkstra’s algorithm, we obtain the shortest paths from every room to the most appropriate emergency exit. Once these paths are calculated, engineers can run simulations and validate, based on path statistics, different cluster configurations. Techniques and tools applied in this research would be helpful in the design and risk management phases of any complex building project.