Analysis of a Methanogen and an Actinobacterium Dominating the Thermophilic Microbial Community of an Electromethanogenic Biocathode.

Electromethanogenesis refers to the bioelectrochemical synthesis of methane from CO2 by biocathodes. In an electromethanogenic system using thermophilic microorganisms, metagenomic analysis along with quantitative real-time polymerase chain reaction and fluorescence in situ hybridization revealed that the biocathode microbiota was dominated by the methanogen Methanothermobacter sp. strain EMTCatA1 and the actinobacterium Coriobacteriaceae sp. strain EMTCatB1. RNA sequencing was used to compare the transcriptome profiles of each strain at the methane-producing biocathodes with those in an open circuit and with the methanogenesis inhibitor 2-bromoethanesulfonate (BrES). For the methanogen, genes related to hydrogenotrophic methanogenesis were highly expressed in a manner similar to those observed under H2-limited conditions. For the actinobacterium, the expression profiles of genes encoding multiheme c-type cytochromes and membrane-bound oxidoreductases suggested that the actinobacterium directly takes up electrons from the electrode. In both strains, various stress-related genes were commonly induced in the open-circuit biocathodes and biocathodes with BrES. This study provides a molecular inventory of the dominant species of an electromethanogenic biocathode with functional insights and therefore represents the first multiomics characterization of an electromethanogenic biocathode.

Petrothermobacter organivorans gen. nov., sp. nov., a thermophilic, strictly anaerobic bacterium of the phylum Deferribacteres isolated from a deep subsurface oil reservoir.

A novel thermophilic, anaerobic, chemoheterotrophic, acetate-oxidizing and iron(III)-, manganese(IV)-, nitrate- and sulfate-reducing bacterium, designated strain ANAT, was isolated from a deep subsurface oil field in Japan (Yabase oil field, Akita Pref.). Cells of strain ANAT were Gram-stain-negative, non-motile, non-spore forming and slightly curved or twisted rods (1.5-5.0 µm long and 0.6-0.7 µm wide). The isolate grew at 25-60 °C (optimum 55 °C) and pH 6.0-8.0 (optimum pH 7.0). The isolate was capable of reducing iron(III), manganese(IV), nitrate and sulfate as an electron acceptor. The isolate utilized a limited range of electron donors such as acetate, lactate, pyruvate and yeast extract for iron reduction. Strain ANAT also used pyruvate, fumarate, succinate, malate, yeast extract and peptone for fermentative growth. The major respiratory quinones were menaquinone-7(H8) and menaquinone-8. The strain contained C18 : 0, iso-C18 : 0 and C16 : 0 as the major cellular fatty acids. The G+C content of the genomic DNA was 34.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain ANAT was closely related to Calditerrivibrio nitroreducens in the phylum Deferribacteres with low sequence similarities (89.5 %), and formed a distinct clade within the family Deferribacteraceae. In addition, the isolate is the first sulfate-reducing member of the phylum Deferribacteres. Based on phenotypic, chemotaxonomic and phylogenetic properties, a novel genus and species, Petrothermobacter organivorans gen. nov., sp. nov., is proposed for the isolate (type strain=ANAT= NBRC 112621T=DSM 105015T).

Bioelectrochemical analyses of the development of a thermophilic biocathode catalyzing electromethanogenesis.

The use of thermophilic microorganisms as biocatalysts for electromethanogenesis was investigated. Single-chamber reactors inoculated with thermophiles and operated at 55 °C showed high CH4 production rates (max. 1103 mmol m(­2) day(­1) at an applied voltage of 0.8 V) with current-capture efficiencies >90%, indicating that thermophiles have high potential as biocatalysts. To improve the electromethanogenic activity, the developed biocathode was transferred to a two-chamber reactor and operated at a poised potential of −0.5 V vs SHE. The CH4 production rates of the biocathode were enhanced approximately 6-fold in 160 h of poised-potential incubation, indicating that the acclimation of the biocathode resulted in performance improvement. Compositional alteration of the cathodic microbiota suggested that a Methanothermobacter-related methanogen and synergistetes- and thermotogae-related bacteria were selected during the acclimation. Cyclic voltammetry of the "acclimated" biocathode showed an augmented cathodic catalytic wave with a midpoint potential at ca. −0.35 V vs SHE. Moreover, the biocathode was able to catalyze electromethanogenesis at −0.35 V vs SHE. These results suggested that the ability of the biocathode to catalyze electromethanogenesis via direct electron transfer was enhanced by the acclimation. This study provides new technological and fundamental information on electromethanogenic bioelectrochemical systems (BESs) that may be extended to other BESs.

Bioelectrochemical analysis of a hyperthermophilic microbial fuel cell generating electricity at temperatures above 80 °C.

We examined whether a hyperthermophilic microbial fuel cell (MFC) would be technically feasible. Two-chamber MFC reactors were inoculated with subsurface microorganisms indigenous to formation water from a petroleum reservoir and were started up at operating temperature 80 °C. The MFC generated a maximum current of 1.3 mA 45 h after the inoculation. Performance of the MFC improved with an increase in the operating temperature; the best performance was achieved at 95 °C with the maximum power density of 165 mWm(-2), which was approximately fourfold higher than that at 75 °C. Thus, to our knowledge, our study is the first to demonstrate generation of electricity in a hyperthermophilic MFC (operating temperature as high as 95 °C). Scanning electron microscopy showed that filamentous microbial cells were attached on the anode surface. The anodic microbial consortium showed limited phylogenetic diversity and primarily consisted of hyperthermophilic bacteria closely related to Caldanaerobacter subterraneus and Thermodesulfobacterium commune.

A thermophilic gram-negative nitrate-reducing bacterium, Calditerrivibrio nitroreducens, exhibiting electricity generation capability.

To exploit the potential diversity of thermophilic exoelectrogens, two-chamber microbial fuel cells (MFCs) were inoculated with thermophilic anaerobic digester sludge and operated at 55 °C without supplementing with exogenous redox mediator. The MFC generated a maximum power density of 823 mW m(-2) after 200 h of operation. Molecular phylogenetic analyses suggested that the microbial population on the anode was dominated by a species closely related to a thermophilic nitrate-reducing bacterium Calditerrivibrio nitroreducens, for which a strain (Yu37-1) has been isolated in pure culture. Thus, a pure culture of the C. nitroreducens strain Yu37-1 was inoculated into MFC to examine the electricity generation capability. Without an exogenous mediator, MFCs stably produced electricity with a maximum power density of 272 mW m(-2) for >400 h of operation. The MFC current recovered to the original level within few hours after medium replacement, suggesting that the electricity generation was caused by the anodic microorganisms. Cyclic voltammetry indicated that redox systems (E3 and Ec) with similar potentials (-0.14 and -0.17 V) made the main contributions to the exoelectrogenic activities of the sludge-derived consortium and C. nitroreducens Yu37-1, respectively. This study undertook the bioelectrochemical characterization of C. nitroreducens as the first example of a thermophilic Gram-negative exoelectrogen.

Main bronchial diverticula in the subcarinal region: their relation to airflow limitations.

BACKGROUND: To date, bronchial diverticula have generally been treated as a pathological condition associated with chronic obstructive pulmonary disease (COPD), although only a limited amount of published information is available on the relationship between bronchial diverticula as depicted by multidetector computed tomography (MDCT) and airflow limitations. PURPOSE: To evaluate the relationship between airflow limitations and main bronchial diverticula in the subcarinal region using spirometry and thin-section MDCT. MATERIAL AND METHODS: A total of 189 consecutive adult patients were retrospectively evaluated based on spirometry and thin-section MDCT of the chest. All examinations were performed at our institution between June and October 2008. The study group included 70 women and 119 men with a mean age of 65 years (range 19-86 years). The relationship between the FEV(1)% and bronchial diverticula in the subcarinal region was analyzed (Student's t-test). RESULTS: The indications for conducting the examinations were pulmonary diseases (82 patients), cardiovascular diseases (22), extrapulmonary malignancies (74), and other conditions (11). A total of 84/189 (44.4%) patients showed bronchial diverticula, and the FEV(1)% of 70/84 (83.3%) patients was above 70. The FEV(1)% of patients with lesions ranged from 26.0 to 97.8 (mean 76.8), whereas the range was 28.1-94.4 (mean 73.7) in those without lesions. There was no significant association between the FEV(1)% and the presence of subcarinal bronchial diverticula (P > 0.05). CONCLUSION: Our data demonstrate that thin-section chest CT commonly demonstrates main bronchial diverticula in the subcarinal region in patients without airflow limitations. We propose that the presence of a small number of tiny bronchial diverticula under the carina may not be a criterion for the diagnosis of COPD.

Evidence for syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the high-temperature petroleum reservoir of Yabase oil field (Japan).

The methanogenic communities and pathways in a high-temperature petroleum reservoir were investigated through incubations of the production water and crude oil, combined with radiotracer experiments and molecular biological analyses. The incubations were conducted without any substrate amendment and under high-temperature and pressurized conditions that mimicked the in situ environment (55°C, 5 MPa). Changes in methane and acetate concentrations during the incubations indicated stoichiometric production of methane from acetate. Rates of hydrogenotrophic methanogenesis measured using [(14)C]-bicarbonate were 42-68 times those of acetoclastic methanogenesis measured using [2-(14) C]-acetate, implying the dominance of methane production by syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the environment. 16S rRNA gene sequence analyses of the incubated production water showed bacterial communities dominated by the genus Thermacetogenium, known as a thermophilic syntrophic acetate-oxidizing bacterium, and archaeal communities dominated by thermophilic hydrogenotrophic methanogens belonging to the genus Methanothermobacter. Furthermore, group-specific real-time PCR assays revealed that 16S rRNA gene copy numbers of the hydrogenotrophic methanogens affiliated with the order Methanobacteriales were almost identical to those of archaeal 16S rRNA genes. This study demonstrates that syntrophic acetate oxidation is the main methanogenic pathway in a high-temperature petroleum reservoir.

Koleobacter methoxysyntrophicus gen. nov., sp. nov., a novel anaerobic bacterium isolated from deep subsurface oil field and proposal of Koleobacteraceae fam. nov. and Koleobacterales ord. nov. within the class Clostridia of the phylum Firmicutes.

An anaerobic thermophilic, rod-shaped bacterium possessing a unique non-lipid sheathed-like structure enveloping a single-membraned cell, designated strain NRmbB1T was isolated from at the deep subsurface oil field located in Yamagata Prefecture, Japan. Growth occurred with 40-60°C (optimum, 55°C), 0-2% (2%), NaCl and pH 6.0-8.5 (8.0). Fermentative growth with various sugars was observed. Glucose-grown cells generated acetate, hydrogen, pyruvate and lactate as the main end products. Syntrophic growth occurred with glucose, pyruvate and 3,4,5-trimethoxybenzoate in the presence of an H2-scavenging partner, and growth on 3,4,5-trimethoxybenzoate was only observed under syntrophic condition. The predominant cellular fatty acids were C16:0, iso-C16:0, anteiso-C15:0, and iso-C14:0. Respiratory quinone was not detected. The genomic G+C content was 40.8mol%. Based on 16S rRNA gene phylogeny, strain NRmbB1T belongs to a distinct order-level clade in the class Clostridia of the phylum Firmicutes, sharing low similarity with other isolated organisms (i.e., 87.5% for top hit Moorella thermoacetica DSM 2955T). In total, chemotaxonomic, phylogenetic and genomic characterization revealed that strain NRmbB1T (=KCTC 25035T, =JCM 39120T) represents a novel species of a new genus. In addition, we also propose the associated family and order as Koleobacteraceae fam. nov and Koleobacterales ord. nov., respectively.

Characteristics and CT features of subcarinal air collections/main bronchial diverticula.

The aim of this study was to evaluate the characteristics and CT features of subcarinal air collections on thin-section multidetector-row computed tomography (MDCT). Two hundred asymptomatic adult subjects without a history of pulmonary disease underwent MDCT. The CT appearances and characteristics of foci of extraluminal air contiguous to the main bronchus in the subcarinal region were retrospectively analysed. Subcarinal air collections were found in 81 of 200 subjects (41%) and were spotty or microtubular in 67 of 81 subjects and rounded or oval in the other 14. Each subcarinal air focus communicated, or seemed to communicate, with the adjacent bronchus in 76 of 81 cases. Our data demonstrate that extraluminal air foci in the subcarinal region are common CT findings and routinely depicted on thin-section MDCT, and that most of these lesions seem to be main bronchial diverticula. Cystic air foci in the subcarinal region should be called subcarinal air cysts. The precise recognition of these cysts improves the ability to avoid misidentification, such as pneumomediastinum.

Quantitative analysis of intracranial hypostasis: comparison of early postmortem and antemortem CT findings.

OBJECTIVE: The purpose of this study was to quantitatively analyze postmortem hypostasis in the intracranial venous sinus on head CT scans compared with the antemortem CT findings in the same patients with the aim of evaluating sedimentation in the heart and great vessels. MATERIALS AND METHODS: A total of 50 patients on whom head CT was performed before and after death were enrolled. Attenuation in the dorsal part of the superior sagittal sinus was measured at the level of the basal ganglia on both antemortem and postmortem CT scans. Increased attenuation in the transverse sinus and cerebellar tentorium and sedimentation in the heart and great vessels were evaluated visually. RESULTS: Attenuation in the dorsal part of the superior sagittal sinus increased significantly (p < 0.0001) between antemortem (42.77 ± 6.23 HU) and postmortem (49.72 ± 10.58 HU) CT in 80% of cases. Increased attenuation of the transverse sinus or cerebellar tentorium was observed in 48% of cases and sedimentation in the heart or great vessels in 62% of cases. Increased attenuation in the superior sagittal sinus was clearly evident in patients with sedimentation in the heart or great vessels (antemortem, 43.81 ± 6.17 HU; postmortem, 54.65 ± 8.51 HU) compared with the patients without evidence of sedimentation (antemortem, 41.06 ± 6.10 HU; postmortem, 41.66 ± 8.57 HU) (p < 0.0001). CONCLUSION: Intracranial hypostasis is a common postmortem CT finding. Radiologists and physicians who interpret postmortem neurologic images should be aware of intracranial hypostasis and differentiate this phenomenon from intracranial hemorrhage.

Correction to: The sternalis muscle: radiologic findings on MDCT.

In the original publication of the article, the seventh author name was incorrectly published as Hidehumi Aoyama. The correct author name should read as Hidefumi Aoyama.

Draft Genome Sequence of a Novel Coriobacteriaceae sp. Strain, EMTCatB1, Reconstructed from the Metagenome of a Thermophilic Electromethanogenic Biocathode.

A draft genome of Coriobacteriaceae sp. strain EMTCatB1 was determined through taxonomic binning of a metagenome of a thermophilic biocathode actively catalyzing electromethanogenesis. This genome will provide information about the biocathode ecosystem, as well as the natural diversity of the Coriobacteriaceae family.

Draft Genome Sequence of Methanothermobacter sp. Strain EMTCatA1, Reconstructed from the Metagenome of a Thermophilic Electromethanogenesis-Catalyzing Biocathode.

A draft genome of Methanothermobacter sp. strain EMTCatA1 was reconstructed from a metagenome of a thermophilic electromethanogenic biocathode. This genome will provide information about methanogens catalyzing methanogenesis at the biocathodes.

High-pressure thermophilic electromethanogenic system producing methane at 5 MPa, 55°C.

Toward applications of bio-electrochemical systems in industrial processes and extreme environments, electromethanogenesis under high-pressure conditions was examined. Stainless-steel single-chamber reactors specifically designed to examine bio-electrochemical reactions under pressurized conditions were inoculated with thermophilic microorganisms originated from an oilfield formation water. The reactors were incubated at 5 MPa, 55°C in fed-batch operational mode with an applied voltage of 0.7 V. In the first few fed-batch cycles, hydrogen was mainly produced. After the third cycle, however, the reactors produced only methane simultaneously with current generation. The methane-production rate of the reactors showed an applied-voltage dependence and increased from 34.9 to 168.4 mmol m-2 day-1 with an increase in the applied voltage from 0.4 to 0.9 V. The efficiency of capturing electrons in the produced methane on average exceeded 70% with the applied voltage of 0.4 V or higher. Cyclic voltammetry further confirmed abilities of the bioelectrodes to catalyze electrochemical reactions at 5 MPa. Performance of the electromethanogenesis system was not altered under lower pressure conditions (1.2 and 2.5 MPa). An exoelectrogenic bacterium affiliated with the genus Thermincola and a methanogen belonging to the genus Methanothermobacter were detected as the dominant species in the bioanode and biocathode microbiotas, respectively. Thus, our results indicated that electromethanogenesis systems could be developed and operated under highly-pressurized conditions, suggesting that applications of the bio-electrochemical system in high-pressure environments (including high-temperature subsurface reservoirs) can be technically feasible.

Localized air foci in the lower thorax in the patients with pneumothorax: skip pneumothoraces.

PURPOSE: To investigate the characteristics and imaging features of localized air foci in the lower thorax in patients with pneumothorax using thin-section multidetector computed tomography. MATERIALS AND METHODS: Of 10,547 consecutive CT examinations comprising the chest, the CT scans of 146 patients with ordinary pneumothoraces were identified and retrospectively evaluated. The study group included 110 male and 36 female patients (mean age, 50 years; range, 1-93 years). All examinations were performed at our institution between January 2009 and December 2009. Cause of pneumothorax was classified as traumatic or non-traumatic. Localized air foci in the lower thorax were defined as being localized air collections in the lower thorax that did not appear to be adjacent to the lung. If these criteria were met, the shape, size, location laterality, and number of foci were evaluated. Associations with trauma, sex, severity of the pneumothorax, and laterality were evaluated using the χ(2) test. All P values <0.05 were considered significant. RESULTS: Localized air foci in the lower thorax presented as slit-like or small ovoid air collections in the lowest part of the pleural space. These foci were observed in 79/146 (54.1%) patients. The traumatic pneumothoraces group showed a higher prevalence of these features than the non-traumatic group. Some foci that were situated in the anterior part mimicked the appearance of free intraperitoneal air. CONCLUSION: Patients with pneumothorax commonly had localized air foci in the lower thorax. Because such foci can mimic pneumoperitoneum, accurate recognition of them is required to avoid confusion with free intraperitoneal air, especially in traumatic cases.

Electrochemical and phylogenetic analyses of current-generating microorganisms in a thermophilic microbial fuel cell.

To explore diversity of thermophilic exoelectrogens, a thermophilic microbial fuel cell was constructed. Population analysis of the anodic microorganisms suggested possible involvement of Caloramator-related bacteria in electricity generation. Pure culture of Caloramator australicus showed electricity-generating ability, indicating that the bacterium is a new thermophilic exoelectrogen.

Bio-electrochemical property and phylogenetic diversity of microbial communities associated with bioelectrodes of an electromethanogenic reactor.

Electromethanogenesis is a new bio-electrochemical reaction potentially useful for energy conversion. As a first step toward its technical application, electromethanogenic reactors were built, and their bio-electrochemical properties were analyzed. Comparisons of the microbial compositions of the electromethanogenic cathode and the current-producing anode suggested an electromethanogenic pathway mediated by exoelectrogenic bacteria.

Carbon dioxide concentration dictates alternative methanogenic pathways in oil reservoirs.

Deep subsurface formations (for example, high-temperature oil reservoirs) are candidate sites for carbon capture and storage technology. However, very little is known about how the subsurface microbial community would respond to an increase in CO2 pressure resulting from carbon capture and storage. Here we construct microcosms mimicking reservoir conditions (55 °C, 5 MPa) using high-temperature oil reservoir samples. Methanogenesis occurs under both high and low CO2 conditions in the microcosms. However, the increase in CO2 pressure accelerates the rate of methanogenesis to more than twice than that under low CO2 conditions. Isotope tracer and molecular analyses show that high CO2 conditions invoke acetoclastic methanogenesis in place of syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis that typically occurs in this environment (low CO2 conditions). Our results present a possibility of carbon capture and storage for enhanced microbial energy production in deep subsurface environments that can mitigate global warming and energy depletion.

The sternalis muscle: radiologic findings on MDCT.

PURPOSE: The purpose of this study was to characterize and determine the prevalence of the sternalis muscle using 64-row multidetector computed tomography (MDCT). MATERIALS AND METHODS: We retrospectively reviewed MDCT chest scans that were performed in a hospital during the course of a month. The study population consisted of 948 consecutive patients (511 males and 467 females). On the MDCT scans the sternalis muscle was defined as the longitudinal muscle lying on and superficial to the pectoralis major muscle. RESULTS: The prevalence of the sternalis muscle was 10.5 %. The muscle was present more frequently in females (13.0 %) compared to males (8.4 %) (P = 0.02). In the majority of patients, the muscle was located longitudinally in the parasternal position; however, in two patients it was positioned across the sternum. One hundred twenty were flat types, while the remaining five had oblique shapes. The muscle mean height, width and depth were 77.9 ± 25.1, 19.4 ± 12.2 and 2.8 ± 1.3 mm, respectively. The muscle was wider in males compared to females (P < 0.001). CONCLUSION: Using MDCT, its prevalence was shown to be 10.5 %. This variant muscle can be differentiated from other pathological structures using its specific characteristic appearance.

Phylogenetic diversity of microbial communities associated with the crude-oil, large-insoluble-particle and formation-water components of the reservoir fluid from a non-flooded high-temperature petroleum reservoir.

The diversity of microbial communities associated with non-water-flooded high-temperature reservoir of the Niibori oilfield was characterized. Analysis of saturated hydrocarbons revealed that n-alkanes in crude oil from the reservoir were selectively depleted, suggesting that crude oil might be mildly biodegraded in the reservoir. To examine if any specific microorganism(s) preferentially attached to the crude oil or the other components (large insoluble particles and formation water) of the reservoir fluid, 16S rRNA gene clone libraries were constructed from each component of the reservoir fluid. The clones in the archaeal libraries (414 clones in total) represented 16 phylotypes, many of which were closely related to methanogens. The bacterial libraries (700 clones in total) were composed of 49 phylotypes belonging to one of 16 phylum-level groupings, with Firmicutes containing the greatest diversity of the phylotypes. In the crude-oil- and large-insoluble-particle-associated communities, a Methanosaeta-related phylotype dominated the archaeal sequences, whereas hydrogenotrophic methanogens occupied a major portion of sequences in the library of the formation-water-associated community. The crude-oil associated bacterial community showed the largest diversity, containing 35 phylotypes, 16 of which were not detected in the other bacterial communities. Thus, although the populations associated with the reservoir-fluid components largely shared common phylogenetic context, a specific fraction of microbial species preferentially attached to the crude oil and insoluble particles.