Iron- and sulfur-oxidizing bacteria

The oldest putative fossils occur as hematite filaments and tubes in jasper-carbonate banded iron formations from the 4280-to 3750-Ma Nuvvuagittuq Supracrustal Belt, Québec. If biological in origin, these filaments might have affinities with modern descendants; however, if abiotic, they could indicate complex prebiotic forms on early Earth. Here, we report images of centimeter-size, autochthonous hematite filaments that are pectinate-branching, parallel-aligned, undulated, and containing Fe 2+-oxides. These microstructures are considered microfossils because of their mineral associations and resemblance to younger microfossils, modern Fe-bacteria from hydrothermal environments, and the experimental products of heated Fe-oxidizing bacteria. Additional clusters of irregular hematite ellipsoids could reflect abiotic processes of silicification, producing similar structures and thus yielding an uncertain origin. Millimeter-sized chalcopyrite grains within the jasper-carbonate rocks have 34 Sand 33 S-enrichments consistent with microbial S-disproportionation and an O 2-poor atmosphere. Collectively, the observations suggest a diverse microbial ecosystem on the primordial Earth that may be common on other planetary bodies, including Mars.

The abandoned Sitarjevec mine represents a specific environment (complete darkness; 10 C) with waters of pH 3 and it contains various ores (e.g. lead, mercury, zinc, iron, copper) and many different minerals (e.g. anglesite, baryte, cinnabar, pyrite, cerussite, quartz, siderite). The aim of this study was to characterize the iron oxide/hydroxide speleothems that show rapid growth of up to 5 cm/year. Their morphological and chemical characterization showed that they have a layered structure with different ferrihydrite minerals (i.e. goethite, feroxyhyte, lepidocrocite). Scanning electron microscopy-energy dispersive X-ray spectrometry confirmed that the surface layers were very porous, while for the inner parts, the bulk was compact. Bacterial populations in these speleothems and their environment were analyzed using 16S rRNA sequencing. These data revealed a great diversity of bacteria, which included 19-34 phyla across different samples. Proteobacteria were dominant in all of the samples (60-95%), although the highest bacterial diversity was seen for a water sample from the base of the speleothem, with 670 different genera and 100 different species detected. Among these there were typical iron-oxidizing bacteria, like Gallionella capsiferriformans, Sideroxydans lithotrophicus, Sphingomonas echinoides, Candidatus Nitrotoga Nitrotoga, Leptospirillum ferrooxidans, and Ferrovum myxofaciens. These iron-oxidizing bacteria were not present in other samples from the mine. Therefore, these bacteria might be involved in the structural growth of these speleothems. The specific bacterial interactions with the minerals under the environmental conditions in the mine need to be further analyzed and evaluated.

Esterases are a class of enzymes that split esters into an acid and an alcohol in a chemical reaction with water, having high potential in pharmaceutical, food and biofuel industrial applications. To advance the understanding of esterases, we have identified and characterized E53, an alkalophilic esterase from a marine bacterium Erythrobacter longus. The crystal structures of wild type E53 and three variants were solved successfully using the X-ray diffraction method. Phylogenetic analysis classified E53 as a member of the family IV esterase. The enzyme showed highest activity against p-nitrophenyl butyrate substrate at pH 8.5-9.5 and 40 • C. Based on the structural feature, the catalytic pocket was defined as R1 (catalytic center), R2 (pocket entrance), and R3 (end area of pocket) regions. Nine variants were generated spanning R1-R3 and thorough functional studies were performed. Detailed structural analysis and the results obtained from the mutagenesis study revealed that mutations in the R1 region could regulate the catalytic reaction in both positive and negative directions; expanding the bottleneck in R2 region has improved the enzymatic activity; and R3 region was associated with the determination of the pH pattern of E53. N166A in R3 region showed reduced activity only under alkaline conditions, and structural analysis indicated the role of N166 in stabilizing the loop by forming a hydrogen bond with L193 and G233. In summary, the systematic studies on E53 performed in this work provide structural and functional insights into alkaliphilic esterases and further our knowledge of these enzymes.

The article says that the formation of pyrophoric deposits on the inner walls of the equipment storage of petroleum and petroleum products is the risk of occurrence of emergency situations. Classification of emergency situations proposed, offered to which emergencies may cause the spontaneous combustion of pyrophoric deposits

Long term data series (1996 through 2009) for trace metals were analyzed from a large number of streams and rivers across Sweden varying in tributary watershed size from 0.05 to 48 193 km 2. The final data set included 139 stream sites with data for arsenic (As), cobalt (Co), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), and vanadium (V). Between 7 % and 46 % of the sites analyzed showed significant trends according to the seasonal Kendall test. However, in contrast to previous studies and deposi-tional patterns, a substantial portion of the trends were positive , especially for V (100 %), As (95 %), and Pb (68 %). Other metals (Zn and Cr) generally decreased, were mixed (Ni and Zn), or had very few trends (Co) over the study period. Trends by region were also analyzed and some showed significant variation between the north and south of Swe-den. Regional trends for both Cu and Pb were positive (60 % and 93 %, respectively) in the southern region but strongly negative (93 % and 75 %, respectively) in the northern region. Kendall's τ coefficients were used to determine dependence between metals and potential in-stream drivers including total organic carbon (TOC), iron (Fe), pH, and sulphate (SO 2− 4). TOC and Fe correlated positively and strongly with As, V, Pb, and Co while pH and SO 2− 4 generally correlated weakly, or not at all with the metals studied.

Filamentous macroscopic algae were observed in slightly acidic to circumneutral (pH 5.9-6.5), metal-rich stream water that leaked out from a former uranium mining district (Ronneburg, Germany). These algae differed in color and morphology and were encrusted with Fedeposits. To elucidate their potential interaction with Fe(II)oxidizing bacteria (FeOB), we collected algal samples at three time points during summer 2013 and studied the algaebacteria-mineral compositions via confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectra, and a 16S and 18S rRNA gene-based bacterial and algae community analysis. Surprisingly, sequencing analysis of 18S rRNA gene regions of green and brown algae revealed high homologies with the freshwater algae Tribonema (99.9-100 %). CLSM imaging indicated a loss of active chloroplasts in the algae cells, which may be responsible for the change in color in Tribonema. Fe(III)-precipitates on algal cells identified as ferrihydrite and schwertmannite by FTIR were associated with microbes and extracellular polymeric substances (EPS)like glycoconjugates. SEM imaging revealed that while the green algae were fully encrusted with Fe-precipitates, the brown algae often exhibited discontinuous series of precipitates. This pattern was likely due to the intercalary growth of algal filaments which allowed them to avoid detrimental encrustation. 16S rRNA gene-targeted studies revealed

Long term data series (1996 through 2009) for trace metals were analyzed from a large number of streams and rivers across Sweden varying in tributary watershed size from 0.05 to 48 193 km 2 . The final data set included 139 stream sites with data for arsenic (As), cobalt (Co), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), and vanadium (V). Between 7 % and 46 % of the sites analyzed showed significant trends according to the seasonal Kendall test. However, in contrast to previous studies and depositional patterns, a substantial portion of the trends were positive, especially for V (100 %), As (95 %), and Pb (68 %). Other metals (Zn and Cr) generally decreased, were mixed (Ni and Zn), or had very few trends (Co) over the study period. Trends by region were also analyzed and some showed significant variation between the north and south of Sweden. Regional trends for both Cu and Pb were positive (60 % and 93 %, respectively) in the southern region but strongly negative (93 % and 75 %, respectively) in the northern region. Kendall's τ coefficients were used to determine dependence between metals and potential in-stream drivers including total organic carbon (TOC), iron (Fe), pH, and sulphate (SO 2− 4 ). TOC and Fe correlated positively and strongly with As, V, Pb, and Co while pH and SO 2− 4 generally correlated weakly, or not at all with the metals studied.