Uranium Biogeochemistry in the Rhizosphere of a Contaminated Wetland.

The objective of this study was to determine if U sediment concentrations in a U-contaminated wetland located within the Savannah River Site, South Carolina, were greater in the rhizosphere than in the nonrhizosphere. U concentrations were as much as 1100% greater in the rhizosphere than in the nonrhizosphere fractions; however and importantly, not all paired samples followed this trend. Iron (but not C, N, or S) concentrations were significantly enriched in the rhizosphere. XAS analyses showed that in both sediment fractions, U existed as UO22+ coordinated with iron(III)-oxides and organic matter. A key difference between the two sediment fractions was that a larger proportion of U was adsorbed to Fe(III)-oxides, not organic matter, in the rhizosphere, where significantly greater total Fe concentrations and greater proportions of ferrihydrite and goethite existed. Based on 16S rRNA analyses, most bacterial sequences in both paired samples were heterotrophs, and population differences were consistent with the generally more oxidizing conditions in the rhizosphere. Finally, U was very strongly bound to the whole (unfractionated) sediments, with an average desorption Kd value (Usediment/Uaqueous) of 3972 ± 1370 (mg-U/kg)/(mg-U/L). Together, these results indicate that the rhizosphere can greatly enrich U especially in wetland areas, where roots promote the formation of reactive Fe(III)-oxides.

Antibiotics, passive smoking, high socioeconomic status and sweetened foods contribute to the risk of paediatric inflammatory bowel disease: A systematic review with meta-analysis.

OBJECTIVE: Genetic and environmental factors influence pathogenesis and rising incidence of paediatric inflammatory bowel disease (PIBD). The aim was to meta-analyse evidence of diet and environmental factors in PIBD. METHODS: A systematic search was conducted to identify diet and environmental factors with comparable risk outcome measures and had been reported in two or more PIBD studies for inclusion in meta-analyses. Those with ≥2 PIBD risk estimates were combined to provide pooled risk estimates. RESULTS: Of 4763 studies identified, 36 studies were included. PIBD was associated with higher risk with exposure to ≥/=4 antibiotic courses (includes prescriptions/purchases/courses), passive smoking, not being breastfed, sugary drink intake, being a non-Caucasian child living in a high-income country and infection history (odds ratio [OR] range: 2-3.8). Paediatric Crohn's disease (CD) was associated with higher risk with exposure to antibiotics during early childhood, ≥/=4 antibiotic courses, high socioeconomic status (SES), maternal smoking, history of atopic conditions and infection history (OR range: 1.6-4.4). A history of infection was also associated with higher risk of paediatric ulcerative colitis (UC) (OR: 3.73). Having a higher number of siblings (≥2) was associated with lower risk of paediatric CD (OR: 0.6) and paediatric UC (OR: 0.7). Pet exposure was associated with lower risk of paediatric UC (OR: 0.5). CONCLUSION: Several factors associated with PIBD risk were identified that could potentially be used to develop a disease screening tool. Future research is needed to address risk reduction in PIBD.

Effect of Siderophore DFOB on U(VI) Adsorption to Clay Mineral and Its Subsequent Reduction by an Iron-Reducing Bacterium.

Uranium mining and nuclear fuel production have led to significant U contamination. Past studies have focused on the bioreduction of soluble U(VI) to insoluble U(IV) as a remediation method. However, U(IV) is susceptible to reoxidation and remobilization when conditions change. Here, we demonstrate that a combination of adsorption and bioreduction of U(VI) in the presence of an organic ligand (siderophore desferrioxamine B, DFOB) and the Fe-rich clay mineral nontronite partially alleviated this problem. DFOB greatly facilitated U(VI) adsorption into the interlayer of nontronite as a stable U(VI)-DFOB complex. This complex was likely reduced by bioreduction intermediates such as the Fe(II)-DFOB complex and/or through electron transfer within a ternary Fe(II)-DFOB-U(VI) complex. Bioreduction with DFOB alone resulted in a mobile aqueous U(IV)-DFOB complex, but in the presence of both DFOB and nontronite U(IV) was sequestered into a solid. These results provide novel insights into the mechanisms of U(VI) bioreduction and the stability of U and have important implications for understanding U biogeochemistry in the environment and for developing a sustainable U remediation approach.

Carbonate Minerals and Dissimilatory Iron-Reducing Organisms Trigger Synergistic Abiotic and Biotic Chain Reactions under Elevated CO2 Concentration.

Increasing CO2 emission has resulted in pressing climate and environmental issues. While abiotic and biotic processes mediating the fate of CO2 have been studied separately, their interactions and combined effects have been poorly understood. To explore this knowledge gap, an iron-reducing organism, Orenia metallireducens, was cultured under 18 conditions that systematically varied in headspace CO2 concentrations, ferric oxide loading, and dolomite (CaMg(CO3)2) availability. The results showed that abiotic and biotic processes interactively mediate CO2 acidification and sequestration through "chain reactions", with pH being the dominant variable. Specifically, dolomite alleviated CO2 stress on microbial activity, possibly via pH control that transforms the inhibitory CO2 to the more benign bicarbonate species. The microbial iron reduction further impacted pH via the competition between proton (H+) consumption during iron reduction and H+ generation from oxidization of the organic substrate. Under Fe(III)-rich conditions, microbial iron reduction increased pH, driving dissolved CO2 to form bicarbonate. Spectroscopic and microscopic analyses showed enhanced formation of siderite (FeCO3) under elevated CO2, supporting its incorporation into solids. The results of these CO2-microbe-mineral experiments provide insights into the synergistic abiotic and biotic processes that alleviate CO2 acidification and favor its sequestration, which can be instructive for practical applications (e.g., acidification remediation, CO2 sequestration, and modeling of carbon flux).

Combined Effects of Fe(III)-Bearing Clay Minerals and Organic Ligands on U(VI) Bioreduction and U(IV) Speciation.

Reduction of U(VI) to U(IV) drastically reduces its solubility and has been proposed as a method for remediation of uranium contamination. However, much is still unknown about the kinetics, mechanisms, and products of U(VI) bioreduction in complex systems. In this study, U(VI) bioreduction experiments were conducted with Shewanella putrefaciens strain CN32 in the presence of clay minerals and two organic ligands: citrate and EDTA. In reactors with U and Fe(III)-clay minerals, the rate of U(VI) bioreduction was enhanced due to the presence of ligands, likely because soluble Fe3+- and Fe2+-ligand complexes served as electron shuttles. In the presence of citrate, bioreduced U(IV) formed a soluble U(IV)-citrate complex in experiments with either Fe-rich or Fe-poor clay mineral. In the presence of EDTA, U(IV) occurred as a soluble U(IV)-EDTA complex in Fe-poor montmorillonite experiments. However, U(IV) remained associated with the solid phase in Fe-rich nontronite experiments through the formation of a ternary U(IV)-EDTA-surface complex, as suggested by the EXAFS analysis. Our study indicates that organic ligands and Fe(III)-bearing clays can significantly affect the microbial reduction of U(VI) and the stability of the resulting U(IV) phase.

Pediatric third liver transplantation-A single-center experience.

BACKGROUND: Pediatric retransplantation is an accepted practice for graft failure and complications in Australasia. As 15% of children require a third transplant, this is a growing cohort with limited data in the literature. METHODS: We review nine patients from the commencement of our transplantation program in 1986 up to 2020 assessing demographics, prognosis, and outcome measures. RESULTS: Third transplant patient survival was comparative to first and second transplant patient survival at 5 years. All deaths were within the post-operative period and secondary to sepsis. Operative times and transfusion volumes were increased at third transplant (1.8 and 4.5 times compared to first transplant, respectively). Learning difficulties and psychological disturbances were prevalent (83% and 66.6%, respectively). CONCLUSIONS: While recent mortality outcomes appear comparable to undergoing a second liver transplant, third transplant operations were more complex. Neurological impairment and psychological disturbance appear to be prevalent and need to be considered in pre-transplant counseling.

Impact of organic acids and sulfate on the biogeochemical properties of soil from urban subsurface environments.

Urban subsurface environments are often different from undisturbed subsurface environments due to the impacts of human activities. For example, deterioration of underground infrastructure can introduce elevated levels of Ca, Fe, and heavy metals into subsurface soils and groundwater. Likewise, leakage from sewer systems can lead to contamination by organic C, N, S, and P. However, the impact of these organic and inorganic compounds on biogeochemical processes including microbial redox reactions, mineral transformations, and microbial community transitions in urban subsurface environments is poorly understood. Here we conducted a microcosm experiment with soil samples from an urban construction site to investigate the possible biotic and abiotic processes impacted when sulfate and acetate or lactate were introduced into an urban subsurface environment. In the top-layer soil (0-0.3 m) microcosms, which were highly alkaline (pH > 10), the major impact was on abiotic processes such as secondary mineral precipitation. In the mid-layer (2-3 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were greatly impacted by the specific organic acid added, and sulfate-reduction was not observed until after Fe(III)-reduction was complete. Near the end of the incubation, some genera related to syntrophic acetate oxidation and methanogenesis were observed in the lactate-amended microcosms. In the bottom-layer (7-8 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were affected by the concentration of amended sulfate. Sulfate-reduction was concurrent with Fe(III)-reduction, suggesting that Fe(II) production was likely due to abiotic reduction of Fe(III) by sulfide produced by microbial sulfate reduction. The slightly acidic initial pH (~5.8) of the mid-soil system was a major factor controlling sequential microbial Fe(III) and sulfate reduction versus parallel Fe(III) and sulfate reduction in the bottom soil system, which had a neutral initial pH (~7.2). 16S rRNA gene-based community analysis revealed a variety of indigenous microbial groups including alkaliphiles, dissimilatory iron and sulfate reducers, syntrophes, and methanogens tightly coupled with, and impacted by, these complex abiotic and biogeochemical processes occurring in urban subsurface environments.

Geochemical and microbial characteristics of seepage water and mineral precipitates in a radwaste disposal facility impacted by seawater intrusion and high alkalinity.

The construction of an underground facility can dramatically change the quality, flow direction, and level of groundwater. It may also impact subsurface microbial composition and activity. Groundwater quality was monitored over eight years in two observational wells near an underground disposal facility on the east coast of South Korea. The results showed dramatic increases in dissolved ions such as O2, Na, Ca, Mg, and SO4 during facility construction. Seepage water samples downgradient from the silos and tunnels, and precipitates deposited along the seepage water flow path were collected to determine the impact inside the disposal facility. X-ray analysis (powder X-ray diffraction (pXRD) and X-ray absorption fine structure (XAFS)) were used to characterize the mineral precipitates. Microbial community composition was determined by 16S rRNA gene sequencing. The seepage water composition was of two types: Ca-Cl and Ca-Na-HCO3. The ratio of Cl and δ18O showed that the Ca-Cl type seepage water was influenced by groundwater mixed with seawater ranging from 2.7% to 15.1%. Various sulfate-reducing bacteria were identified in the Ca-Cl type seepage water, exhibiting relatively high sulfate content from seawater intrusion. Samples from the Ca-Na-HCO3 type seepage water had an extremely high pH (>10) and abundance of Hydrogenophaga. The precipitates observed along the flow path of the seepage water included calcite, ferrihydrite, green rust, and siderite, depending on seepage water chemistry and microbial activity. This study suggests that the construction of underground structures creates distinct, localized geochemical conditions (e.g., high alkalinity, high salinity, and oxic conditions), which may impact microbial communities. These biogeochemical changes may have undesirable large-scale impacts such as water pump clogging. An understanding of the process and long-term monitoring are essential to assess the safety of underground facilities.

Controls on Iron Reduction and Biomineralization over Broad Environmental Conditions as Suggested by the Firmicutes Orenia metallireducens Strain Z6.

Microbial iron reduction is a ubiquitous biogeochemical process driven by diverse microorganisms in a variety of environments. However, it is often difficult to separate the biological from the geochemical controls on bioreduction of Fe(III) oxides. Here, we investigated the primary driving factor(s) that mediate secondary iron mineral formation over a broad range of environmental conditions using a single dissimilatory iron reducer, Orenia metallireducens strain Z6. A total of 17 distinct geochemical conditions were tested with differing pH (6.5-8.5), temperature (22-50 °C), salinity (2-20% NaCl), anions (phosphate and sulfate), electron shuttle (anthraquinone-2,6-disulfonate), and Fe(III) oxide mineralogy (ferrihydrite, lepidocrocite, goethite, hematite, and magnetite). The observed rates and extent of iron reduction differed significantly with kint between 0.186 and 1.702 mmol L-1 day-1 and Fe(II) production ranging from 6.3% to 83.7% of the initial Fe(III). Using X-ray absorption and scattering techniques (EXAFS and XRD), we identified and assessed the relationship between secondary minerals and the specific environmental conditions. It was inferred that the observed bifurcation of the mineralization pathways may be mediated by differing extents of Fe(II) sorption on the remaining Fe(III) minerals. These results expand our understanding of the controls on biomineralization during microbial iron reduction and aid the development of practical applications.

Outcomes for children after second liver transplantations are similar to those after first transplantations: a binational registry analysis.

OBJECTIVE: To assess long term graft and patient survival after donor liver retransplantation in children in Australia and New Zealand during 1986-2017; to determine the factors that influence survival. DESIGN: Retrospective cohort analysis (registry data). SETTING, PARTICIPANTS: Australia and New Zealand Liver Transplant Registry data for all liver retransplantations in children (under 18 years of age), 1986-2017, in all four paediatric and six adult liver transplantation centres in the two countries. MAIN OUTCOME MEASURES: Graft and patient survival at one, 5, 10 and 15 years. RESULTS: 142 liver retransplantations were undertaken in children (59 during 1986-2000, 83 during 2001-2017). Kaplan-Meier survival analysis indicated that survival was significantly greater during 2001-2017 than 1986-2000 (P < 0.001). During 2001-2017, graft survival one year after retransplantation was 84%, at 5 years 75%, at 10 years 70%, and at 15 years 54%; patient survival was 89% at one year, 87% at 5 years, 87% at 10 years, and 71% at 15 years. Median time between transplantations was 0.2 years (IQR, 0.03-1.4 years) during 1986-2000, and 1.8 years (IQR, 0.1-6.8 years) during 2001-2017 (P = 0.002). The proportion of graft failures that involved split grafts was larger during 2001-2017 (35 of 83, 42%) than 1986-2000 (10 of 59, 17%). Graft type, cause of graft failure, and number of transplants did not influence survival following retransplantation. CONCLUSION: Survival for children following retransplantation is excellent. Graft survival is similar for split and whole grafts. Children on the liver waiting list requiring retransplantation should have the same access to donor grafts as children requiring a first transplant.

History of paediatric gastroenterology in Australia.

Paediatric gastroenterology in Australia has undergone remarkable changes over the more than six decades since Charlotte Anderson's pioneering work, and is now a well-established specialty in its own right. Australian paediatric gastroenterologists have made important contributions nationally and internationally.

U(VI) Reduction by Biogenic and Abiotic Hydroxycarbonate Green Rusts: Impacts on U(IV) Speciation and Stability Over Time.

Green rusts (GRs) are redox active FeII-FeIII minerals that form in the environment via various biotic and abiotic processes. Although both biogenic (BioGR) and abiotic (ChemGR) GRs have been shown to reduce UVI, the dynamics of the transformations and the speciation and stability of the resulting UIV phases are poorly understood. We used carbonate extraction and XAFS spectroscopy to investigate the products of UVI reduction by BioGR and ChemGR. The results show that both GRs can rapidly remove UVI from synthetic groundwater via reduction to UIV. The initial products in the ChemGR system are solids-associated UIV-carbonate complexes that gradually transform to nanocrystalline uraninite over time, leading to a decrease in the proportion of carbonate-extractable U from ∼95% to ∼10%. In contrast, solid-phase UIV atoms in the BioGR system remain relatively extractable, nonuraninite UIV species over the same reaction period. The presence of calcium and carbonate in groundwater significantly increase the extractability of UIV in the BioGR system. These data provide new insights into the transformations of U under anoxic conditions in groundwater that contains calcium and carbonate, and have major implications for predicting uranium stability within redox dynamic environments and designing approaches for the remediation of uranium-contaminated groundwater.

Application of an in-situ soil sampler for assessing subsurface biogeochemical dynamics in a diesel-contaminated coastal site during soil flushing operations.

Subsurface biogeochemistry and contaminant dynamics during the remediation of diesel-contamination by in-situ soil flushing were investigated at a site located in a coastal region. An in-situ sampler containing diesel-contaminated soils separated into two size fractions (<0.063- and <2-mm) was utilized in two monitoring wells: DH1 (located close to the injection and extraction wells for in-situ soil flushing) and DH2 (located beyond sheet piles placed to block the transport of leaked diesel). Total petroleum hydrocarbon (TPH) concentrations and biogeochemical properties were monitored both in soil and groundwater for six months. A shift occurred in the groundwater type from Ca-HCO3 to Na-Cl due to seawater intrusion during intense pumping, while the concentrations of Ni, Cu, Co, V, Cr, and Se increased substantially following surfactant (TWEEN 80) injection. The in-situ sampler with fine particles was more sensitive to variations in conditions during the remedial soil flushing process. In both wells, soil TPH concentrations in the <0.063-mm fraction were much higher than those in the <2-mm fraction. Increases in soil TPH in DH1 were consistent with the expected outcomes following well pumping and surfactant injection used to enhance TPH extraction. However, the number of diesel-degrading microorganisms decreased after surfactant injection. 16S-rRNA gene-based analysis also showed that the community composition and diversity depended on both particle size and diesel contamination. The multidisciplinary approach to the contaminated site assessments showed that soil flushing with surfactant enhanced diesel extraction, but negatively impacted in-situ diesel biodegradation as well as groundwater quality. The results also suggest that the in-situ sampler can be an effective monitoring tool for subsurface biogeochemistry as well as contaminant dynamics.

Are We Overdoing Pediatric Lower Gastrointestinal Endoscopy?

INTRODUCTION: Lower gastrointestinal endoscopy (LGIE)/colonoscopy is frequently performed for rectal bleeding, recurrent abdominal pain, and the diagnosis of inflammatory bowel disease (IBD). Although these are common indications, the causes of isolated rectal bleeding and recurrent abdominal pain in the otherwise well child have not been described. METHODS: A retrospective analysis of patients who had had an LGIE/colonoscopy from January 2001 to December 2010 was performed. The following data were collected: demographic data, indication, distance reached, macroscopic findings, microscopic findings, diagnosis, additional procedures, and complications. RESULTS: There were a total of 999 colonoscopies. The colonoscopy was normal in 390 of 999 (39%). The commonest indication for colonoscopy was a diagnosis of suspected IBD, 449 of 999 (45%). IBD was confirmed in 282 of 449 (63%), but colonoscopy was normal in 143 of 449 (32%) of suspected IBD. Colonoscopy was performed for rectal bleeding in 197 of 999 (20%) of whom 141 of 197 (72%) were normal. There were 46 (5%) colonoscopies performed for recurrent abdominal pain, which were all normal. Our completion rate to the cecum and beyond was 521 of 999 (52%). Our perforation rate during the 10 years was 0.2%. CONCLUSIONS: Colonoscopy is a safe procedure in pediatrics; however, 39% of colonoscopies in this series were normal. Many of these could have been avoided by eliminating colonoscopy in patients with recurrent abdominal pain in the absence of other clinical features, conservative management with laxatives for those with fresh blood per rectum typical of anal fissures, and fecal calprotectin screening before endoscopy in patients with suspected IBD.

Reducing the incidence of hepatic artery thrombosis in pediatric liver transplantation: Effect of microvascular techniques and a customized anticoagulation protocol.

We aimed to assess the incidence of HAT over three eras following implementation of microvascular techniques and a customized anticoagulation protocol in a predominantly cadaveric split liver transplant program. We retrospectively reviewed pediatric liver transplants performed between April 1986 and 2016 and analyzed the incidence HAT over three eras. In E1, 1986-2008, each patient received a standard dose of 5 U/kg/h of heparin and coagulation profiles normalized passively. In E2, 2008-2012, microvascular techniques were introduced. In E3, 2012-2016, in addition, a customized anticoagulation protocol was introduced which included replacement of antithrombin 3, protein C and S, and early heparinization. A total of 317 liver transplants were completed during the study period, with a median age of 31.7 months. In E1, 22% of grafts were cadaveric in situ split grafts, while the second and third eras used split grafts in 59.0% and 64.9% of cases, respectively. HAT occurred in 9.5% in the first era, 11.5% (P=.661) in the second, and dropped to 1.8% in the third era (P=.043). A routine anticoagulation protocol has significantly reduced the incidence of HAT post-liver transplantation in children in a predominantly cadaveric in situ split liver transplant program.

Early Posthepatoportoenterostomy Predictors of Native Liver Survival in Biliary Atresia.

OBJECTIVES: Most infants with biliary atresia (BA) require liver transplantation (LT) after hepatoportoenterostomy (HPE), including those who initially clear jaundice. The aim of the present study was to identify clinical and routine laboratory factors in infants with BA post-HPE that predict native liver survival at 2 years. METHODS: A retrospective cohort study was conducted in 217 patients with BA undergoing HPE in Sydney, Australia and Toronto, Canada between January 1986 and July 2009. Univariate and multivariate logistic regression using backwards-stepwise elimination identified variables at 3 months after HPE most associated with 2-year native liver survival. RESULTS: Significant variables (P < 0.05) on univariate analysis included serum total bilirubin (TB) and albumin at 3 months post-HPE, bridging fibrosis or cirrhosis on initial liver biopsy, ascites of <3 months post-HPE, type 3 BA anatomy, age at HPE of >45 days, change in length z scores within 3 months of HPE, and center. On multivariate analysis, TB (P < 0.0001) and albumin (P = 0.02) at 3 months post-HPE, and center (P = 0.0003) were independently associated with native liver survival. Receiver operating characteristic analysis revealed an optimal cut-off value of TB <74 µmol/L (4.3 mg/dL; area under the receiver operating characteristic curve 0.8990) and serum albumin level >35 g/L (3.5 mg/dL; area under the receiver operating characteristic curve 0.7633) to predict 2-year native liver survival. TB and albumin levels 3 months post-HPE defined 3 groups (1: TB ≤74 µmol/L, albumin >35 g/L; 2: TB ≤74 µmol/L, albumin ≤35 g/L; 3: TB >74 µmol/L) with distinct short- and long-term native liver survival rates (log-rank P < 0.001). Length z scores 3 months post-HPE were poorer for group 2 than group 1 (-0.91 vs -0.30, P = 0.0217) with similar rates of coagulopathy. CONCLUSIONS: Serum TB and albumin levels 3 months post-HPE independently predicted native liver survival in BA when controlling for center. Serum albumin level <35 g/L in infants with BA who were no longer jaundiced at 3 months post-HPE was a poor prognostic indicator. Poorer linear growth and absence of significant coagulopathy suggest a role for early aggressive nutritional therapy in this group.

Family Impact and Infant Emotional Outcomes Following Diagnosis of Serious Liver Disease or Transplantation in Infancy.

OBJECTIVES: Research is lacking into the emotional effects on families of serious chronic illness in infants. We examined the effect of the diagnosis of serious liver disease in infants upon parent psychological symptoms and family functioning. We hypothesized that parent psychological symptoms, family functioning, and father engagement will predict infant emotional outcomes. METHODS: Parents of infants recently diagnosed with serious liver disease completed validated questionnaires about parent stress, family function, impact of the illness on the family, and father engagement. The measures were repeated after 1 year, with the addition of the Child Behavior Checklist (CBCL). RESULTS: Parents of 37 infants participated. Parent stress and family functioning scores were not elevated. Parent psychological symptoms, family function, and father engagement did not predict infant outcome. For mothers, infant diagnosis other than biliary atresia, number of outpatient visits, and impact of the illness on the family explained 32% of the variation in CBCL (P = 0.001). For fathers, socioeconomic status, infant diagnosis other than biliary atresia, whether the infant had had a transplant, and impact of the illness on the family explained 44% of the variation in CBCL (P < 0.001). CONCLUSIONS: Parents and families appear to be resilient in coping with serious infant illness. Infant diagnosis other than biliary atresia and parental perceptions of high impact of the illness on the family are indicators of negative emotional outcomes for infants with serious liver disease. Psychosocial interventions for infants with chronic illness should target reducing the impact of illness on the family.

Orenia metallireducens sp. nov. Strain Z6, a Novel Metal-Reducing Member of the Phylum Firmicutes from the Deep Subsurface.

A novel halophilic and metal-reducing bacterium, Orenia metallireducens strain Z6, was isolated from briny groundwater extracted from a 2.02 km-deep borehole in the Illinois Basin, IL. This organism shared 96% 16S rRNA gene similarity with Orenia marismortui but demonstrated physiological properties previously unknown for this genus. In addition to exhibiting a fermentative metabolism typical of the genus Orenia, strain Z6 reduces various metal oxides [Fe(III), Mn(IV), Co(III), and Cr(VI)], using H2 as the electron donor. Strain Z6 actively reduced ferrihydrite over broad ranges of pH (6 to 9.6), salinity (0.4 to 3.5 M NaCl), and temperature (20 to 60°C). At pH 6.5, strain Z6 also reduced more crystalline iron oxides, such as lepidocrocite (γ-FeOOH), goethite (α-FeOOH), and hematite (α-Fe2O3). Analysis of X-ray absorption fine structure (XAFS) following Fe(III) reduction by strain Z6 revealed spectra from ferrous secondary mineral phases consistent with the precipitation of vivianite [Fe3(PO4)2] and siderite (FeCO3). The draft genome assembled for strain Z6 is 3.47 Mb in size and contains 3,269 protein-coding genes. Unlike the well-understood iron-reducing Shewanella and Geobacter species, this organism lacks the c-type cytochromes for typical Fe(III) reduction. Strain Z6 represents the first bacterial species in the genus Orenia (order Halanaerobiales) reported to reduce ferric iron minerals and other metal oxides. This microbe expands both the phylogenetic and physiological scopes of iron-reducing microorganisms known to inhabit the deep subsurface and suggests new mechanisms for microbial iron reduction. These distinctions from other Orenia spp. support the designation of strain Z6 as a new species, Orenia metallireducens sp. nov. IMPORTANCE: A novel iron-reducing species, Orenia metallireducens sp. nov., strain Z6, was isolated from groundwater collected from a geological formation located 2.02 km below land surface in the Illinois Basin, USA. Phylogenetic, physiologic, and genomic analyses of strain Z6 found it to have unique properties for iron reducers, including (i) active microbial iron-reducing capacity under broad ranges of temperatures (20 to 60°C), pHs (6 to 9.6), and salinities (0.4 to 3.5 M NaCl), (ii) lack of c-type cytochromes typically affiliated with iron reduction in Geobacter and Shewanella species, and (iii) being the only member of the Halanaerobiales capable of reducing crystalline goethite and hematite. This study expands the scope of phylogenetic affiliations, metabolic capacities, and catalytic mechanisms for iron-reducing microbes.

Tepidibacillus decaturensis sp. nov., a microaerophilic, moderately thermophilic iron-reducing bacterium isolated from 1.7 km depth groundwater.

A Gram-stain-negative, microaerophilic rod-shaped organism designated as strain Z9T was isolated from groundwater of 1.7 km depth from the Mt. Simon Sandstone of the Illinois Basin, Illinois, USA. Cells of strain Z9T were rod shaped with dimensions of 0.3×(1-10) µm and stained Gram-negative. Strain Z9T grew within the temperature range 20-60 °C (optimum at 30-40 °C), between pH 5 and 8 (optimum 5.2-5.8) and under salt concentrations of 1-5 % (w/v) NaCl (optimum 2.5 % NaCl). In addition to growth by fermentation and nitrate reduction, this strain was able to reduce Fe(III), Mn(IV), Co(III) and Cr(VI) when H2 or organic carbon was available as the electron donor, but did not actively reduce oxidized sulfur compounds (e.g. sulfate, thiosulfate or S0). The G+C content of the DNA from strain Z9T was 36.1 mol%. Phylogenetic analysis of the 16S rRNA gene from strain Z9T showed that it belongs to the class Bacilli and shares 97 % sequence similarity with the only currently characterized member of the genus Tepidibacillus, T.fermentans. Based on the physiological distinctness and phylogenetic information, strain Z9T represents a novel species within the genus Tepidibacillus, for which the name Tepidibacillus decaturensis sp. nov. is proposed. The type strain is Z9T (=ATCC BAA-2644T=DSM 103037T).