Environmental, hydrological, and social impacts of coal and nonmetal minerals mining operations.

Mining and mineral exploration has many effects on the surrounding environment. The present study reviews the hydrological and environmental impacts of coal and nonmetal mining operations by mine lifecycle stages and facility patterns. Further, a critical review of regulations and policies in South Korea focusing on the mining-water interaction, conservation, and management was performed to emphasize the current state of legislation in the country. The counties where mining was the primary employer in Gangwon-do province in South Korea were assessed for the mining impact on the community's social life and com-pared to the non-mining counties in the same province. The results of the comparative study showed the less education, healthcare and employment chances in mining counties than the adjacent counties with no mining activities.

Microbial mediated reaction of dimethylarsinic acid in wetland water and sediments.

The biogeochemical reactions of dimethylarsinic acid (DMAs(V)) were investigated using simulated wetland systems in a laboratory. DMAs(V) was injected into the wetland water, and the As concentrations in the water, plants, and sediments were monitored. Aqueous and solid-phase As speciation was evaluated, and the results revealed that the DMAs(V) was completely transported to the sediments and plants. X-ray absorption spectroscopic measurement of the As in the sediment revealed that approximately 85-95% of As existed as inorganic As species, demonstrating the important role of microorganisms in the biogeochemical reaction of DMAs(V). The influences of microbes were further investigated in smaller batches under aerobic and anaerobic conditions. The microbial batch results showed that DMAs(V) demethylation reduced the total aqueous As concentration, demonstrating that As(V) has higher affinity to wetland sediment than DMAs(V). The redox conditions were also revealed as an important controlling factor of the As reaction and, under anaerobic conditions, we observed the presence of the most toxic form of inorganic As(III) in the aqueous phase. Although this study reports one example from a specific wetland, the important roles of the redox conditions and microbial influences were identified from the comprehensive analysis of As speciation and mass balance.

Effects of arginase inhibition on myocardial Ca2+ and contractile responses.

Nitric oxide (NO) is thought to increase cardiac contractility by increasing cytosolic Ca2+ concentration ([Ca2+ ]cyt ) during excitation. Alternatively, NO could increase the sensitivity of the contractile response to [Ca2+ ]cyt (Ca2+ sensitivity). Arginase regulates NO production by competing with NO synthase (NOS), and thus, arginase inhibition should increase cardiac contractility by increasing NO production. We hypothesized that arginase inhibition increases cardiac contractility by increasing both [Ca2+ ]cyt and Ca2+ sensitivity. [Ca2+ ]cyt and contractile (sarcomere length [SL] shortening) responses to electrical stimulation were measured simultaneously in isolated rat cardiomyocytes using an IonOptix system. In the same cardiomyocytes, measurements were obtained at baseline, following 3-min exposure to an arginase inhibitor (S-[2-boronoethyl]-l-cysteine; BEC) and following 3-min exposure to BEC plus a NOS inhibitor (NG -nitro-l-arginine-methyl ester; l-NAME). These responses were compared to time-matched control cardiomyocytes that were untreated. Compared to baseline, BEC increased the amplitude and the total amount of evoked [Ca2+ ]cyt , and the extent and velocity of SL shortening in cardiomyocytes, whereas addition of l-NAME mitigated these effects. The [Ca2+ ]cyt at 50% contraction and relaxation were not different across treatment groups indicating no effect of BEC on Ca2+ sensitivity. The [Ca2+ ]cyt and SL shortening responses in time-matched controls did not vary with time. Arginase inhibition by BEC significantly increased the amplitude and the total amount of evoked [Ca2+ ]cyt , and the extent and velocity of SL shortening in cardiomyocytes, but did not affect Ca2+ sensitivity. These effects of BEC were mitigated by l-NAME. Together, these results indicate an effect of NO on [Ca2+ ]cyt responses that then increase the contractile response of cardiomyocytes.

Conformational control of two-dimensional gold nanoparticle arrays in a confined geometry within a vesicular wall.

The two-dimensional (2D) assembly of gold nanoparticles (AuNPs) in a confined geometry is a rare phenomenon that has not been experimentally verified for complex systems. In this study, this process was investigated in detail using two types of block copolymers with hydrophobic and hydrophilic blocks and a series of AuNPs of three different sizes protected by hydrophobic ligands. In aqueous solutions, the selected block copolymers self-assembled into vesicular nanostructures with a hydrophobic domain in the wall, which functions as a confined geometrical space for hydrophobic AuNPs (i.e., it exerts a confinement effect and restricts the movement of AuNPs). Small-angle X-ray scattering studies revealed that AuNPs of different sizes assembled differently in the same confined geometry of the vesicular wall. In addition, optimal conditions for the formation of a regular NP array in the hydrophobic domain were determined. The AuNPs successfully self-assembled into a regular 2D lattice structure, forming a shell around the vesicle, when their size matched the thickness of the hydrophobic domain of the vesicular nanostructure. This study provides guidelines for the fabrication of nanoparticle arrays with controlled structures, which could enhance the functionality of materials and their physical properties.

Arsenic removal characteristics of natural Mn-Fe binary coating on waste filter sand from a water treatment facility.

In this study, the arsenic (As) removal characteristics of a Mn-Fe binary coating formed on waste sand filter of an acid mine drainage treatment facility are investigated. Owing to the Mn-Fe binary coating forming on the surfaces of the sand grains, its potential for arsenic removal, particularly As(III), was evaluated and characterized through batch experiments and x-ray absorption spectroscopy. Sorption isotherms reveal that the Mn-Fe binary coating exhibits comparable removal efficiencies for As(III) and As(V) under low initial As concentrations. However, at higher initial As(III) and As(V) concentrations, the As(III) removal efficiency increases because of newly formed active adsorption sites from reductive dissolution of Mn. The oxidation of the As(III) and reduction of the Mn oxide phases are verified through As K-edge and Mn K-edge X-ray absorption near edge fine structure analysis. The outstanding As(III) removal efficiency of the Mn-Fe binary coating suggests synergy of Fe- and Mn-oxides, highlighting a potential application for this coating system. The natural formation of binary coating through acid mine drainage treatment reported in this study indicates that similar coating can form naturally in other environments, thus, providing plausible natural attenuation processes for arsenic immobilization.

Precise control of heat-treatment conditions to improve the catalytic performance of V2O5/TiO2 for H2S removal.

The purpose of this study is to investigate the influences of atmospheric gas and temperature while preparing V2O5/TiO2 catalysts to find a suitable heat-treatment method to improve catalytic performance during the process of H2S removal. The catalysts prepared by wet-impregnation were heat-treated at different temperatures (400 or 600 â„ƒ) under various atmospheres (Air, N2, or H2). The catalytic tests demonstrated that the catalyst heat-treated at 400 â„ƒ under N2 atmosphere (N-400) possessed excellent catalytic activities regarding H2S conversion (96.4%) and sulfur yield (89.1%). The characterization results revealed that the mild reducing condition employed for N-400 led to the formation of partially reduced V2O5 crystals and a strong V-Ti interaction owing to the anatase TiO2 phase, resulting in the high oxygen vacancies on the catalyst surface. However, severe reducing conditions (H2 or N2 with 600 â„ƒ) or the higher temperature (600 â„ƒ) induced highly reduced V2O5-x or rutile TiO2 related to a weak V-Ti interaction, respectively, which facilitated lower oxygen vacancies. This study is the first to demonstrate the significance of a precisely controlled heat-treatment to enhance catalytic performance for H2S removal.

Effects of TNFα on Dynamic Cytosolic Ca2 + and Force Responses to Muscarinic Stimulation in Airway Smooth Muscle.

Previously, we reported that in airway smooth muscle (ASM), the cytosolic Ca2+ ([Ca2+] cyt ) and force response induced by acetyl choline (ACh) are increased by exposure to the pro-inflammatory cytokine tumor necrosis factor α (TNFα). The increase in ASM force induced by TNFα was not associated with an increase in regulatory myosin light chain (rMLC20) phosphorylation but was associated with an increase in contractile protein (actin and myosin) concentration and an enhancement of Ca2+ dependent actin polymerization. The sensitivity of ASM force generation to elevated [Ca2+] cyt (Ca2+ sensitivity) is dynamic involving both the shorter-term canonical calmodulin-myosin light chain kinase (MLCK) signaling cascade that regulates rMLC20 phosphorylation and cross-bridge recruitment as well as the longer-term regulation of actin polymerization that regulates contractile unit recruitment and actin tethering to the cortical cytoskeleton. In this study, we simultaneously measured [Ca2+] cyt and force responses to ACh and explored the impact of 24-h TNFα on the dynamic relationship between [Ca2+] cyt and force responses. The temporal delay between the onset of [Ca2+] cyt and force responses was not affected by TNFα. Similarly, the rates of rise of [Ca2+] cyt and force responses were not affected by TNFα. The absence of an impact of TNFα on the short delay relationships between [Ca2+] cyt and force was consistent with the absence of an effect of [Ca2+] cyt and force on rMLC20 phosphorylation. However, the integral of the phase-loop plot of [Ca2+] cyt and force increased with TNFα, consistent with an impact on actin polymerization and, contractile unit recruitment and actin tethering to the cortical cytoskeleton.

Wafer-Scale Unidirectional Alignment of Supramolecular Columns on Faceted Surfaces.

The long-range alignment of supramolecular structures must be engineered as a first step toward advanced nanopatterning processes aimed at miniaturizing features to dimensions below 5 nm. This study introduces a facile method of directing the orientation of supramolecular columns over wafer-scale areas using faceted surfaces. Supramolecular columns with features on the sub-5 nm scale were highly aligned in a direction orthogonal to that of the facet patterning on unidirectional and nanoscopic faceted surface patterns. This unidirectional alignment of supramolecular columns is also observed by varying the thickness of the supramolecular film or by altering the dimensions of the facet pattern. The ordering behavior of the supramolecular columns can be attributed to the triangular depth profile of the bottom facet pattern. Furthermore, this directed self-assembly principle allows for the continuous alignment of supramolecular structures across ultralarge distances on flexible patterned substrates.

Self-Assembly of 2D Gold Nanoparticle Superlattice in a Polymer Vesicle Layer Driven by Hydrophobic Interaction.

Self-assembly of gold nanoparticles (AuNPs) into highly ordered superstructures provides a promising route toward fabricating materials with new functionalities or enhanced physical properties. Although self-assembly of AuNPs has garnered significant research attention recently, a highly ordered superlattice of AuNPs under a low concentration in a confined geometry formed by nonfunctionalized materials has not been reported. Herein, we investigate the self-assembly of a 2D AuNPs superlattice in a polymer vesicle layer using hydrophobic interactions, which exhibits centered rectangular lattice symmetry. To create the highly ordered AuNPs superlattice, the P(EGx-b-iPGEy) block copolymers that form the thickness of the hydrophobic vesicle layer comparable to the size of the AuNP are used as a template to control the AuNP degree of freedom. To the best of our knowledge, this study provides the first demonstration of a centered rectangular structure formation of AuNPs at the vesicle layer in 2D confined geometry.

Association of Intereye Visual-Sensitivity Asymmetry With Progression of Primary Open-Angle Glaucoma.

Purpose: To investigate the relationship between intereye visual field defect (VFD) asymmetry and subsequent VF progression in primary open-angle glaucoma (POAG). Methods: Moderate-stage patients with POAG (226 eyes of 113 patients) with a single hemifield defect were followed for 8.7 years. Participants were categorized into three groups by initial VF pattern: (1) unilateral VFD, (2) bilateral VFD within same hemifield (superior-superior, inferior-inferior), (3) bilateral VFD within opposite hemifield (superior-inferior). The mean deviation (MD) difference between the intereye was defined as the intereye MD asymmetry index (iMAI). Intereye visual-sensitivity difference within the same hemifield was calculated as the intereye hemifield visual-sensitivity asymmetry index. Functional progression was detected by Glaucoma Progression Analysis. The overall rate of MD change and the association between new indices were evaluated by linear regression. A Kaplan-Meier survival analysis was performed and the factors associated with glaucoma progression were evaluated by Cox proportional hazard modeling. Results: Unilateral VFD eyes and bilateral VFD eyes within opposite VF hemifield showed significant progression and faster rate of MD change compared with bilateral VFD eyes within same VF hemifield (71.1% vs. 45.9% vs. 21.1% [P = 0.001]; -1.27 dB/y vs. -0.64 dB/y vs. -0.32 dB/y [P = 0.001]). Unilateral VFD eyes showed the fastest time to VF progression compared with other groups (P = 0.002). A faster rate of MD change was associated with greater intereye MD asymmetry index (P = 0.001) and greater intereye hemifield visual-sensitivity asymmetric index (P = 0.031), which were significant risk factors for glaucoma progression (all P < 0.001). Conclusions: Among POAG eyes with comparable hemifield VFDs, eyes without a corresponding hemifield defect in the fellow eye showed faster rates of progression compared with those with a corresponding hemifield defect.

Dynamic cytosolic Ca2+ and force responses to muscarinic stimulation in airway smooth muscle.

During agonist stimulation of airway smooth muscle (ASM), agonists such as ACh induce a transient increase in cytosolic Ca2+ concentration ([Ca2+]cyt), which leads to a contractile response [excitation-contraction (E-C) coupling]. Previously, the sensitivity of the contractile response of ASM to elevated [Ca2+]cyt (Ca2+ sensitivity) was assessed as the ratio of maximum force to maximum [Ca2+]cyt. However, this static assessment of Ca2+ sensitivity overlooks the dynamic nature of E-C coupling in ASM. In this study, we simultaneously measured [Ca2+]cyt and isometric force responses to three concentrations of ACh (1, 2.6, and 10 µM). Both maximum [Ca2+]cyt and maximum force responses were ACh concentration dependent, but force increased disproportionately, thereby increasing static Ca2+ sensitivity. The dynamic properties of E-C coupling were assessed in several ways. The temporal delay between the onset of ACh-induced [Ca2+]cyt and onset force responses was not affected by ACh concentration. The rates of rise of the ACh-induced [Ca2+]cyt and force responses increased with increasing ACh concentration. The integral of the phase-loop plot of [Ca2+]cyt and force from onset to steady state also increased with increasing ACh concentration, whereas the rate of relaxation remained unchanged. Although these results suggest an ACh concentration-dependent increase in the rate of cross-bridge recruitment and in the rate of rise of [Ca2+]cyt, the extent of regulatory myosin light-chain (rMLC20) phosphorylation was not dependent on ACh concentration. We conclude that the dynamic properties of [Ca2+]cyt and force responses in ASM are dependent on ACh concentration but reflect more than changes in the extent of rMLC20 phosphorylation.

Molecular Weight-Dependent, Flexible Phase Behaviors of Amphiphilic Block Copolymer/Additive Complexes in Aqueous Solution.

Pluronic amphiphilic block copolymers, well known to have a phase behavior can be controlled by external conditions, have a wide range of potential for applications such as nanotemplates or nanobuilding blocks. However, the phase behaviors of Pluronic block copolymer/additive complexes with highly ordered phases have not been fully investigated. Here, we report the unusual molecular weight-dependent self-assembly of Pluronic block copolymer/additive complexes. Depending on the temperature and additive, Pluronic P65 block copolymer with a lower molecular weight showed the closed loop-like (CLL) phase behavior with the disorder-order-disorder-order phase transition in aqueous solution, whereas Pluronic P105 and P85 block copolymers with higher molecular weights underwent highly ordered continuous phase transitions with face centered cubic (FCC), hexagonal, and lamellar phases. It is expected that the specific phase behavior of the block copolymer/additive complex can be applied in optical devices such as nanotemplates or optical sensors for a highly ordered superlattice. Furthermore, this study provides a new route to control the phase behavior of the block copolymers without a complicated process.

Field demonstration of solar-powered electrocoagulation water treatment system for purifying groundwater contaminated by both total coliforms and arsenic.

People who drink groundwater in rural areas of Southeast Asia are exposed to pathogens and arsenic (As)-related health problems. A water treatment system consisting of electrocoagulation reactors, using iron (Fe) electrodes and a filtration tank, was designed to treat complex contaminated groundwater for drinking. Its applicability was demonstrated near the Red River in Vietnam. The water treatment system reduced 10.3 CFU/mL of total coliform and 376 µg/L of As(III) in the groundwater to 0 CFU/mL and 6.68 µg/L, respectively. Total coliforms were attenuated by Fe(II) infiltration or enmeshed during Fe precipitate formation. Of the total As, 43% formed As(III) complexation with the Fe precipitates and the other 57% was oxidized to As(V) then adsorbed to Fe precipitates. The Fe precipitates, containing total coliforms and As, were separated from the discharge water in the filtration tank. The system required 49 W of power to operate, which equates to 423 kWh/year, to continuously purify 0.5 t water/day. This requirement was powered by a 380-750 W solar panel, without external energy supply, making the water treatment system an appropriate option for addressing drinking water problems in rural areas.

Morphological characteristics of parapapillary atrophy and subsequent visual field progression in primary open-angle glaucoma.

BACKGROUND/AIMS: To investigate the associations between the morphological characteristics of beta-zone parapapillary atrophy (ß-zone PPA) and subsequent visual field (VF) progression in eyes with primary open-angle glaucoma (POAG). METHODS: One hundred and twenty-one POAG eyes with ß-zone PPA along with 48 normal eyes with ß-zone PPA were included. ß-zone PPA area was calculated based on the PPA pixel area/optic-disc pixel area ratio and the optical coherence tomography (OCT)-measured disc area. ß-zone PPA margin irregularity was quantified as a function of both area (A) and perimeter (P, calculated as 1/(4πA/P²)). VF progression was defined using standard automated perimetry's guided progression analysis software. RESULTS: Of the 121 POAG eyes, 49 (40.5%) showed VF progression during the 10.1±1.9 years of follow-up. The baseline ß-zone PPA area was similar among the three groups (Progressors, Non-progressors and Controls, p=0.995). However, the ß-zone PPA irregularity index was significantly higher in the Progressors (p<0.001). The cumulative probability of VF progression was greater in the higher PPA irregularity index group (p<0.001, log-rank test). A Cox proportional hazards model showed the significant influences of optic disc haemorrhage (HR: 2.661, p=0.034) and higher baseline PPA irregularity index (HR: 1.455, p=0.007) on subsequent progression. CONCLUSIONS: In POAG eyes, baseline ß-zone PPA margin regularity was significantly associated with subsequent VF progression. Irregular margin of ß-zone PPA might be the mark of vulnerability in the parapapillary area to further glaucomatous damage.

Explaining the Rationale of Deep Learning Glaucoma Decisions with Adversarial Examples.

PURPOSE: To illustrate what is inside the so-called black box of deep learning models (DLMs) so that clinicians can have greater confidence in the conclusions of artificial intelligence by evaluating adversarial explanation on its ability to explain the rationale of DLM decisions for glaucoma and glaucoma-related findings. Adversarial explanation generates adversarial examples (AEs), or images that have been changed to gain or lose pathologic characteristic-specific traits, to explain the DLM's rationale. DESIGN: Evaluation of explanation methods for DLMs. PARTICIPANTS: Health screening participants (n = 1653) at the Seoul National University Hospital Health Promotion Center, Seoul, Republic of Korea. METHODS: We trained DLMs for referable glaucoma (RG), increased cup-to-disc ratio (ICDR), disc rim narrowing (DRN), and retinal nerve fiber layer defect (RNFLD) using 6430 retinal fundus images. Surveys consisting of explanations using AE and gradient-weighted class activation mapping (GradCAM), a conventional heatmap-based explanation method, were generated for 400 pathologic and healthy patient eyes. For each method, board-trained glaucoma specialists rated location explainability, the ability to pinpoint decision-relevant areas in the image, and rationale explainability, the ability to inform the user on the model's reasoning for the decision based on pathologic features. Scores were compared by paired Wilcoxon signed-rank test. MAIN OUTCOME MEASURES: Area under the receiver operating characteristic curve (AUC), sensitivities, and specificities of DLMs; visualization of clinical pathologic changes of AEs; and survey scores for locational and rationale explainability. RESULTS: The AUCs were 0.90, 0.99, 0.95, and 0.79 and sensitivities were 0.79, 1.00, 0.82, and 0.55 at 0.90 specificity for RG, ICDR, DRN, and RNFLD DLMs, respectively. Generated AEs showed valid clinical feature changes, and survey results for location explainability were 3.94 ± 1.33 and 2.55 ± 1.24 using AEs and GradCAMs, respectively, of a possible maximum score of 5 points. The scores for rationale explainability were 3.97 ± 1.31 and 2.10 ± 1.25 for AEs and GradCAM, respectively. Adversarial example provided significantly better explainability than GradCAM. CONCLUSIONS: Adversarial explanation increased the explainability over GradCAM, a conventional heatmap-based explanation method. Adversarial explanation may help medical professionals understand more clearly the rationale of DLMs when using them for clinical decisions.

Thermal effect on the leachability of extraframework Co2+ in zeolite X.

A partially Co2+-exchanged zeolite X was thermally treated to simulate the effect of decay heat on the leachability of extraframework Co2+. To have a mechanistic insight into thermal effect, X-ray diffraction, scanning electron microscopy, 27Al magic angle spinning nuclear magnetic resonance spectroscopy, and Co K-edge X-ray absorption spectroscopy were employed with leaching tests. Although thermal treatment at ≤ 600 °C did not lead to the collapse of zeolite framework, it removed H2O molecules from the coordination shell of extraframework Co2+, which in turn changed its coordination structure in a way to strengthen the interaction between Co2+ and the lattice oxygens. In leaching tests, the sample treated at higher temperature for a longer period showed less remobilized Co2+ by forming a Co(OH)2-like surface precipitate and a Co hydrotalcite-like phase. Notably, the formation of the latter phase indicated the abstraction of the framework Al, the extent of which increased with the treatment temperature and duration. Two mechanisms, the concurrent extraction of Al with Co2+ remobilization and the hydrolysis-promoted Al abstraction, were proposed to account for thermally promoted dealumination. This study suggests that the exposure of Co2+-exchanged zeolite X to decay heat lessen the risk of extraframework Co2+ to be reintroduced into groundwater.

Aging effects on fractionation and speciation of redox-sensitive metals in artificially contaminated soil.

Artificially contaminated soil is often used in laboratory experiments as a substitute for actual field contaminated soils. In the preparation and use of laboratory contaminated soils, questions remain as to how much and how long metals remain in labile form and in their oxidation state during the contamination process. Therefore, the objectives of this study were to determine if the speciation of added contaminants can be retained in the original form and to observe the change in lability of each element with aging time. In this study, natural soil was artificially polluted with five redox-sensitive toxic elements in their oxidized or reduced forms, i.e., As(III)/As(V), Sb(III)/Sb(V), Cr(III)/Cr(VI), Mo(VI), and W(V). Metal distribution was measured in progressive chemical fractionation using sequential extraction methods in contaminated soils after 3, 100, and 300 days of aging. The results indicated that the more strongly bound fraction of metals increased by day 100; whereas the fractions were not significantly different from those in the 300-day-aged soil. Among five metals, the ratio of weakly-bound fractions remained highest in As- and lowest in Cr-contaminated soils. The W(VI)-contaminated soil showed strong sorption without changes in speciation during aging. The oxidized or reduced metal species converged to occur as a single species under given soil conditions, regardless of the initial form of metal used to spike the soil. Both As and Sb existed as their oxidized form while Cr existed as its reduced form. The results of this study may provide a useful and practical guideline for artificial soil contamination.

Normal-tension Glaucoma Management: A Survey of Glaucoma Sub-specialists in Korea.

PURPOSE: To investigate the current management patterns of glaucoma subspecialists with regard to normal-tension glaucoma (NTG) in Korea and to determine the effect of the two largest NTG trials on their clinical practice. METHODS: A questionnaire survey was sent to glaucoma subspecialist members of the Korean Glaucoma Society. The questionnaire concerned regular practice with respect to NTG and the extent to which it has been influenced by the Collaborative Normal-tension Glaucoma Study and the Low-pressure Glaucoma Treatment Study (LoGTS). RESULTS: A total of 134 glaucoma subspecialists completed the survey, with a response rate of 56%. The survey reported that 88% and 78% of glaucoma subspecialists were familiar with the Collaborative Normal-tension Glaucoma Study and the LoGTS, respectively. With respect to mild or moderate NTG, most of the respondents (87%-91%) tended to treat their patients immediately without waiting for structural or functional progression. Among the respondents, 47 indicated that the LoGTS results-according to which, 20% of the respondents tended to use brimonidine more often-affected their management. The first-choice topical drugs for NTG were prostaglandin analogues (76%), brimonidine (9%), beta-blockers (8%), and topical carbonic anhydrase inhibitor (6%). CONCLUSIONS: Regarding mild-to-moderate NTG, Korean glaucoma subspecialists tended to initiate treatment without waiting for further progression. The impact of the LoGTS on NTG management was not dominant in clinical practice in Korea. Prostaglandin analogs are the most frequently selected first-choice drugs for the management of NTG in Korea.

Genomic and Physiological Properties of a Facultative Methane-Oxidizing Bacterial Strain of Methylocystis sp. from a Wetland.

Methane-oxidizing bacteria are crucial players in controlling methane emissions. This study aimed to isolate and characterize a novel wetland methanotroph to reveal its role in the wetland environment based on genomic information. Based on phylogenomic analysis, the isolated strain, designated as B8, is a novel species in the genus Methylocystis. Strain B8 grew in a temperature range of 15 °C to 37 °C (optimum 30-35 °C) and a pH range of 6.5 to 10 (optimum 8.5-9). Methane, methanol, and acetate were used as carbon sources. Hydrogen was produced under oxygen-limited conditions. The assembled genome comprised of 3.39 Mbp and 59.9 mol% G + C content. The genome contained two types of particulate methane monooxygenases (pMMO) for low-affinity methane oxidation (pMMO1) and high-affinity methane oxidation (pMMO2). It was revealed that strain B8 might survive atmospheric methane concentration. Furthermore, the genome had various genes for hydrogenase, nitrogen fixation, polyhydroxybutyrate synthesis, and heavy metal resistance. This metabolic versatility of strain B8 might enable its survival in wetland environments.