Natural Organic Matter (NOM) in Aquatic Systems: Interactions with Radionuclides (234Th (IV), 129 I) and Biofilms

A series of laboratory and field investigations were carried out to elucidate the importance of natural organic matter in aquatic systems, i.e., trace element scavenging (e.g., 234Th) by exopolymeric substances (EPS), formation of biofilms, as well as interactions with 129I. A method involving cross flow ultrafiltration, followed by a three-step cartridge soaking and stirred-cell diafiltration, was developed for isolating EPS from phytoplankton cultures, especially in seawater media. EPS isolated from a marine diatom, Amphora sp. was then subjected to semi-quantitative (e.g., carbohydrate, proteins) and quantitative analysis (e.g., neutral sugars, acidic sugars, sulfate). It appeared that Th (IV) binding by EPS was dominated by the acidic polysaccharides of fraction. For EPS of biofilms collected from polluted streams, hydrophobic proteins were the most abundant components in EPS, followed by more hydrophilic carbohydrates. However, chemical composition of carbohydrates or proteins, i.e., monosaccharides and amino acids, respectively, varied with environmental conditions and substrata applied, which suggests that the formation of biofilms on different substrates is regulated by specific properties of microorganisms, environmental conditions and nature of substratum. No correlation between relative hydrophobicity of substratum and development of biofilm was found in this study. A sensitive and rapid GC-MS method was developed to enable the determination of isotopic ratios (129I/127I) of speciated iodine in natural waters. At the F-area of the Savannah River Site (SRS), iodine species in the groundwater consisted of 48.8 percent iodide, 27.3 percent iodate and 23.9 percent organo-iodine. Each of these iodine species exhibited vastly different transport behavior in the column experiments using surface soil from the SRS. Results demonstrated that mobility of iodine species depended greatly on the iodine concentration, mostly due to the limited sorptive capacity for anions of the soil. EPS, especially enzymes (e.g., haloperoxidases) could facilitate the incorporation of iodide to natural organic carbon. At high input concentrations of iodate (78.7 μM), iodate was found to be completely reduced and subsequently followed the transport behavior of iodide. The marked reduction of iodate was probably associated with natural organic carbon and facilitated by bacteria, besides inorganic reductants (e.g., Fe2 ) in sediments and pore water

The Role of Microbial Exopolymers in Determining the Fate of Oil and Chemical Dispersants in the Ocean

The production of extracellular polymeric substances (EPS) by planktonic microbes can influence the fate of oil and chemical dispersants in the ocean through emulsification, degradation, dispersion, aggregation, and/or sedimentation. In turn, microbial community structure and function, including the production and character of EPS, is influenced by the concentration and chemical composition of oil and chemical dispersants. For example, the production of marine oil snow and its sedimentation and flocculent accumulation to the seafloor were observed on an expansive scale after the Deepwater Horizon oil spill in the Northern Gulf of Mexico in 2010, but little is known about the underlying control of these processes. Here, we review what we do know about microbially produced EPS, how oil and chemical dispersant can influence the production rate and chemical and physical properties of EPS, and ultimately the fate of oil in the water column. To improve our response to future oil spills, we need a better understanding of the biological and physiochemical controls of EPS production by microbes under a range of environmental conditions, and in this paper, we provide the key knowledge gaps that need to be filled to do so

Superoxide Production by a Manganese-Oxidizing Bacterium Facilitates Iodide Oxidation

The release of radioactive iodine (i.e., iodine-129 and iodine-131) from nuclear reprocessing facilities is a potential threat to human health. The fate and transport of iodine are determined primarily by its redox status, but processes that affect iodine oxidation states in the environment are poorly characterized. Given the difficulty in removing electrons from iodide (I(−)), naturally occurring iodide oxidation processes require strong oxidants, such as Mn oxides or microbial enzymes. In this study, we examine iodide oxidation by a marine bacterium, Roseobacter sp. AzwK-3b, which promotes Mn(II) oxidation by catalyzing the production of extracellular superoxide (O(2)(−)). In the absence of Mn(2+), Roseobacter sp. AzwK-3b cultures oxidized ∼90% of the provided iodide (10 μM) within 6 days, whereas in the presence of Mn(II), iodide oxidation occurred only after Mn(IV) formation ceased. Iodide oxidation was not observed during incubations in spent medium or with whole cells under anaerobic conditions or following heat treatment (boiling). Furthermore, iodide oxidation was significantly inhibited in the presence of superoxide dismutase and diphenylene iodonium (a general inhibitor of NADH oxidoreductases). In contrast, the addition of exogenous NADH enhanced iodide oxidation. Taken together, the results indicate that iodide oxidation was mediated primarily by extracellular superoxide generated by Roseobacter sp. AzwK-3b and not by the Mn oxides formed by this organism. Considering that extracellular superoxide formation is a widespread phenomenon among marine and terrestrial bacteria, this could represent an important pathway for iodide oxidation in some environments

Effects of Engineered Nanoparticles on the Assembly of Exopolymeric Substances from Phytoplankton

The unique properties of engineered nanoparticles (ENs) that make their industrial applications so attractive simultaneously raise questions regarding their environmental safety. ENs exhibit behaviors different from bulk materials with identical chemical compositions. Though the nanotoxicity of ENs has been studied intensively, their unintended environmental impacts remain largely unknown. Herein we report experimental results of EN interactions with exopolymeric substances (EPS) from three marine phytoplankton species: Amphora sp., Ankistrodesmus angustus and Phaeodactylum tricornutum. EPS are polysaccharide-rich anionic colloid polymers released by various microorganisms that can assemble into microgels, possibly by means of hydrophobic and ionic mechanisms. Polystyrene nanoparticles (23 nm) were used in our study as model ENs. The effects of ENs on EPS assembly were monitored with dynamic laser scattering (DLS). We found that ENs can induce significant acceleration in Amphora sp. EPS assembly; after 72 hours EN-EPS aggregation reached equilibrium, forming microscopic gels of ∼4–6 µm in size. In contrast, ENs only cause moderate assembly kinetic acceleration for A. angustus and P. tricornutum EPS samples. Our results indicate that the effects of ENs on EPS assembly kinetics mainly depend on the hydrophobic interactions of ENs with EPS polymers. The cycling mechanism of EPS is complex. Nonetheless, the change of EPS assembly kinetics induced by ENs can be considered as one potential disturbance to the marine carbon cycle

Anomaly Detection of Control Moment Gyroscope Based on Working Condition Classification and Transfer Learning

The process of human exploration of the universe has accelerated, and aerospace technology has developed rapidly. The health management and prognosis guarantee of spacecraft systems has become an important basic technology. However, with thousands of telemetry data channels and massive data scales, spacecraft systems are increasingly complex. The anomaly detection that relied on simple threshold judgment and expert manual annotation in the past is no longer applicable. In addition, the particularity of the anomaly detection task leads to the lack of fault data for training. Therefore, a data-driven deep transfer learning-based approach is needed for rapid analysis and accurate detection of large-scale data. The control moment gyroscope (CMG) is a significant inertial actuator in the process of large-scale, long-life spacecraft in-orbit operation and mission execution. Its anomaly detection plays a major role in the prevention and elimination of early failures. Based on the research of SincNet and Long Short-Term Memory (LSTM) networks, this paper proposed a Sinc-LSTM neural network based on transfer learning and working condition classification for CMG anomaly detection. First, a two-stage pre-training method is proposed to alleviate the data imbalance, using the Mars Reconnaissance Orbiter (MRO) dataset and a satellite dataset from NASA. Second, the Sinc-LSTM network is designed to enhance the local fitting and long-period memory ability of the model for CMG time series data. Finally, a dynamic threshold judgment anomaly detection method based on working condition classification is designed to accommodate threshold changes for CMG full-cycle anomaly detection. The method is validated on the spacecraft CMG dataset

Dorsal Fin Spines as a Non-invasive Alternative Calcified Structure for Microelemental Studies in Atlantic Bluefin Tuna

Chemical signatures in calcified structures of fishes represent natural tags of chemical and physical characteristics of the environment. The suitability of dorsal spines of Atlantic bluefin tuna (Thunnus thynnus) was investigated as an alternative non-invasive structure to otoliths. The spatial and temporal variability of trace elements was examined, for the first time, throughout the annual growth increments (i.e. translucent and opaque bands) of Bluefin tuna spines from the Bay of Biscay. Four scanning-ablation line transects were drawn and examined using LA-ICPMS to test for differences in tracer concentrations for each spine sections. Firstly, results confirm the questionable spatial stability of tracers in dorsal fin spines. Secondly, most of the elements analyzed 88Sr, 137Ba, 24Mg, 55Mn, 7Li (biological essential elements), 66Zn and 65Cu (priority pollutants) were consistenly found above the limit of detection (LOD). Strontium and Barium showed a similar pattern throughout annuli with concentrations significantly higher in the translucent bands in the second annulus (i.e. second winter). The concentration of Magnesium displayed an increasing pattern with annulus with no differences between translucent and opaque bands. In contrast, the concentration of Manganese showed a decreasing pattern throughout annuli, with concentrations significantly higher in the opaque bands (i.e. summer bands) regardless of annulus. Lithium, Copper and Zinc showed unclear pattern, although the concentration of Zinc seems to be in sync with the deposition of annuli currently interpreted in the ageing process. Findings indicate that the chemical signature of certain biologically essential elements is preserved stable in the dorsal fin spines strengthening its use as a non-invasive alternative structure for chemistry studies in Atlantic bluefin tuna

Iodide Accumulation by Aerobic Bacteria Isolated from Subsurface Sediments of a 129I-Contaminated Aquifer at the Savannah River Site, South Carolina ▿

129I is of major concern because of its mobility in the environment, excessive inventory, toxicity (it accumulates in the thyroid), and long half-life (∼16 million years). The aim of this study was to determine if bacteria from a 129I-contaminated oxic aquifer at the F area of the U.S. Department of Energy's Savannah River Site, SC, could accumulate iodide at environmentally relevant concentrations (0.1 μM I−). Iodide accumulation capability was found in 3 out of 136 aerobic bacterial strains isolated from the F area that were closely related to Streptomyces/Kitasatospora spp., Bacillus mycoides, and Ralstonia/Cupriavidus spp. Two previously described iodide-accumulating marine strains, a Flexibacter aggregans strain and an Arenibacter troitsensis strain, accumulated 2 to 50% total iodide (0.1 μM), whereas the F-area strains accumulated just 0.2 to 2.0%. Iodide accumulation by FA-30 was stimulated by the addition of H2O2, was not inhibited by chloride ions (27 mM), did not exhibit substrate saturation kinetics with regard to I− concentration (up to 10 μM I−), and increased at pH values of <6. Overall, the data indicate that I− accumulation likely results from electrophilic substitution of cellular organic molecules. This study demonstrates that readily culturable, aerobic bacteria of the F-area aquifer do not accumulate significant amounts of iodide; however, this mechanism may contribute to the long-term fate and transport of 129I and to the biogeochemical cycling of iodine over geologic time

Comparative Evaluation of Sediment Trap and Th-234-derived POC Fluxes From the Upper Oligotrophic Waters of the Gulf of Mexico and the Subtropical Northwestern Pacific Ocean

To better understand the inter-relationships between particulate organic carbon (POC) fluxes and phytoplankton and bacteria biomass and production, we compared POC fluxes determined in sediment traps and approaches based on size-fractionated (1-10, 10-50, 50-150 and \u3e150 mu m) suspended particulate Th-234 and POC concentrations in oligotrophic sections of the Gulf of Mexico during August 2005 and May 2006 and in the oligotrophic northwestern Pacific Ocean during 2009. In 2005, the sediment trap POC flux near the bottom of the euphotic zone (120 m) ranged from 71 to 94 mg C m(-2) day(-1), while Th-234-derived POC fluxes using POC/Th-234 ratios in the 10-50 mu m and 50-150 mu m varied from 71 to 150 mg C m-2 day-1. In 2006, the sediment trap POC flux at 120 m ranged from 24 to 67 mg C m(-2) day(-1), while the 234Th-derived POC fluxes in the 10-50 mu m fraction were comparable or somewhat higher, ranging from 71 to 119 mg C m(-2) day-1. The POC fluxes in 2006, calculated by using POC/234Th ratios in the 1-10 mu m and the 50-150 mu m fractions were much higher, ranging from 847 to 1369 mg C m(-2) day(-1). Correlations with biological and chemical parameters support a likely mechanism of sinking aggregates of haptophytes (0.2-20 mu m) of higher density held together by Th-complexing and uronic acid containing exopolymeric substances. The observations that 234Th (and POC) is mainly associated with medium-sized (10-15 mu m) suspended particles rather than larger (50-150 mu m) ones may be caused by the use of a one-filter method and standard filtration and processing procedures that were applied here for collecting suspended particles. This then raises the question of what constitutes representative material from the ocean that settles on the characteristic time scale of 234Th. As a comparison, size-fractionated trap-collected particles in the oligotrophic northwestern Pacific Ocean showed that the 10-50 mu m fraction contained the largest proportion of POC (22-41%), followed by the 50-150 mu m (22-37%). the \u3e150 mu m (15-27%), and the 1-10 mu m (17-23%) fraction. The partitioning of 234Th in trap-collected particles was slightly different from that of POC, with the 1-10 mu m fraction representing the largest proportion (27-48%) of Th-234 flux. Together, the \u3c50 mu m particles contributed, on average, 52 +/- 6% of POC, which suggests that the POC/Th-234 ratios traditionally derived from large (\u3e50 mu m) pump-collected particles may not accurately reflect the majority of sinking particles. Therefore, estimated POC fluxes may be significantly biased using a conventional 234Th based approach, i.e., using POC/Th-234 ratios from a single filter obtained from large (\u3e50 mu m) pump-collected particles. (C) 2010 Elsevier B.V. All rights reserved

CD39-Expressing CD8⁺ T Cells as a New Molecular Marker for Diagnosis and Prognosis of Esophageal Squamous Cell Carcinoma

We aimed to explore the effect of CD39 expression on CD8+ T cells and on the diagnosis and prognosis of esophageal squamous cell carcinoma (ESCC). The independent prognostic factors for the surgical specimens of the 95 ESCC patients were screened by multivariate Cox regression analysis. Differential gene expression analysis was performed by the NetworkAnalyst platform based on data from the Gene Expression Omnibus (GEO). The expression of CD39 on CD8+ T cells in the CK+ region was higher in cancer tissue than in paracancerous tissue (p = 0.011), and high CD39-expressing CD8+ T cells in the CK+ region (HR, 2.587; p = 0.033) and high CD39-expressing CD8+ T cells in the CK− region (HR, 3.090; p = 0.008) were independent risk factors for prognosis in ESCC patients; the expression of ENTPD1 was upregulated in ESCC tissues compared to normal tissues (adjusted p 2 fold change = 1.99), and its expression was significantly positively correlated with the expression of PDCD1, CTLA4, and HAVCR2. High CD39-expressing CD8+ T cells can be used as a new molecular marker for the diagnosis and prognosis of ESCC, and the restoration of partially exhausted CD8+ T cells by inhibiting CD39 may be a new strategy for treating ESCC