Structural characterization of diabolic acid-based tetraester, tetraether and mixed ether/ester, membrane-spanning lipids of bacteria from the order Thermotogales

The distribution of core lipids in the membranes of nine different species of the order Thermotogales, one of the early and deep branching lineages in the Bacteria, were examined by HPLC/MS and demonstrated to consist of membrane-spanning diglycerol lipids comprised of diabolic acid-derived alkyl moieties. In the Thermotoga species the core membrane lipids are characterized by the presence of both ester and ether bonds, whereas in the phylogenetically more distinct Thermosipho and Fervidobacterium spp. only ester bonds occur. A tentative biosynthetic route for the biosynthesis of these membrane-spanning lipids is proposed. Since species of the order Thermotogales are assumed to have occurred early during the evolution of life on Earth, as suggested by its position in the phylogenetic tree of life, these data suggest that the ability to produce both ether and ester glycerol membrane lipids developed relatively early during microbial evolution

Mycosporine-glutamicol-glucoside: A natural UV-absorbing secondary metabolite of rock-inhabiting microcolonial fungi

Microcolonial ascomycetes are known to inhabit bare rock surfaces in cold and hot deserts and thus are habitually exposed to high levels of solar radiation. Several of these stress-tolerant fungal isolates, cultivated in the laboratory under daylight illumination, were studied for the presence of effective UV-radiation protection substances. Liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses allowed for efficient separation and structure clarification of two mycosporines. It was demonstrated that both mycosporine-glutamicol-glucoside and mycosporine-glutaminol-glucoside are natural and constitutive secondary metabolites of microcolonial fungi. The function and relation of these substances in the fungal cell are discussed

2D reactive transport simulations of CO2 streams containing impurities in a saline aquifer, Heletz, Israel

In order to evaluate the chemical impacts of CO2 stream impurities on reservoir rocks, 2D reactive transport simulations using the code TOUGHREACT V3.0 were performed. The underlying reservoir properties are based on in-situ data from the CO2 injection test site Heletz, Israel. Two different CO2 compositions (mole fractions 99 % CO2 + 1 % SO2 and 98.8 % CO2 + 1 % SO2 + 0.2 % NO2, respectively) were chosen to represent oxidising impurities. Different modelling approaches, namely trace gas transport (TGT) and additional brine injection (ABI), were applied to investigate the influence of these modelling approaches on qualitative and quantitative simulation results. The simulations using either approach show an accumulation of SO2 and NO2 close to the injection well due to the preferential dissolution of these acidic impurities compared to CO2. Both modelling approaches indicate the same general chemical impact and related mineral reactions. Within the affected rock volume a distinct ankerite to anhydrite conversion occurs, which slightly enhances porosity. While the same qualitative conclusions independently from the chosen modelling approach were obtained, the quantitative magnitude of mineral conversion and the spatial extent of impurity affected rock material depend on the chosen modelling approach and thus need further investigation with respect to e.g. validation by field test data. (C) 2017 The Authors. Published by Elsevier Ltd

Potential impacts on groundwater resources of deep CO2 storage

Research into carbon dioxide (CO2) geological storage has been carried out over two decades, as part of studies to evaluate the feasibility of Carbon Dioxide Capture and Storage (CCS). Recently, there has been an increasing focus on potential impacts to surrounding geological formations and particularly, shallow aquifers and associated potable groundwater resources. Potential leakage of CO2 in supercritical and gaseous form from onshore or nearshore deep saline formations (DSF), or of the associated formation brines, is frequently cited as a key risk scenario for the overlying or neighbouring shallower groundwater. To date, the impact of CO2 storage has mainly been studied at near-well and reservoir scale, whereas risks in the context of regional multilayered groundwater systems have not yet been systematically assessed. Recent studies have begun to address this topic, using hydrodynamic and geochemical modelling approaches, and have identified several potential mechanisms that can lead to negative impact on groundwater quantity and/or quality. The IEA Greenhouse Gas R&D Programme (IEAGHG) recently commissioned the CO2GeoNet Association to undertake a literature review and unpublished original work on this topic, with the aim of summarising ‘state of the art’ knowledge and identifying knowledge gaps and research priorities in this field. This paper is a summary of this report