Impact of Concurrent aerobic-anaerobic Methanotrophy on Methane Emission from Marine Sediments in Gas Hydrate Area.

Microbial methane oxidation has a significant impact on the methane flux from marine gas hydrate areas. However, the environmental fate of methane remains poorly constrained. We quantified the relative contributions of aerobic and anaerobic methanotrophs to methane consumption in sediments of the gas hydrate-bearing Sakata Knoll, Japan, by in situ geochemical and microbiological analyses coupled with 13C-tracer incubation experiments. The anaerobic ANME-1 and ANME-2 species contributed to the oxidation of 33.2 and 1.4% methane fluxes at 0-10 and 10-22 cm below the seafloor (bsf), respectively. Although the aerobic Methylococcaceae species consumed only 0.9% methane flux in the oxygen depleted 0.0-0.5 cmbsf zone, their metabolic activity was sustained down to 6 cmbsf (based on rRNA and lipid biosyntheses), increasing their contribution to 10.3%. Our study emphasizes that the co-occurrence of aerobic and anaerobic methanotrophy at the redox transition zone is an important determinant of methane flux.

Quest for Nitrous Oxide-reducing Bacteria Present in an Anammox Biofilm Fed with Nitrous Oxide.

N2O-reducing bacteria have been examined and harnessed to develop technologies that reduce the emission of N2O, a greenhouse gas produced by biological nitrogen removal. Recent investigations using omics and physiological activity approaches have revealed the ecophysiologies of these bacteria during nitrogen removal. Nevertheless, their involvement in| |anammox processes remain unclear. Therefore, the present study investigated the identity, genetic potential, and activity| |of N2O reducers in an anammox reactor. We hypothesized that N2O is limiting for N2O-reducing bacteria| |and an| |exogeneous N2O supply enriches as-yet-uncultured N2O-reducing bacteria. We conducted a 1200-day incubation of N2O-reducing bacteria in an anammox consortium using gas-permeable membrane biofilm reactors (MBfRs), which efficiently supply N2O in a bubbleless form directly to a biofilm grown on a gas-permeable membrane. A 15N tracer test indicated that the supply of N2O resulted in an enriched biomass with a higher N2O sink potential. Quantitative PCR and 16S rRNA amplicon sequencing revealed Clade II nosZ type-carrying N2O-reducing bacteria as protagonists of N2O sinks. Shotgun metagenomics showed the genetic potentials of the predominant Clade II nosZ-carrying bacteria, Anaerolineae and Ignavibacteria in MBfRs. Gemmatimonadota and non-anammox Planctomycetota increased their abundance in MBfRs despite their overall lower abundance. The implication of N2O as an inhibitory compound scavenging vitamin B12, which is essential for the synthesis of methionine, suggested its limited suppressive effect on the growth of B12-dependent bacteria, including N2O reducers. We identified Dehalococcoidia and Clostridia as predominant N2O sinks in an anammox consortium fed exogenous N2O because of the higher metabolic potential of vitamin B12-dependent biosynthesis.

Stable States of a Microbial Community Are Formed by Dynamic Metabolic Networks with Members Functioning to Achieve Both Robustness and Plasticity.

A more detailed understanding of the mechanisms underlying the formation of microbial communities is essential for the efficient management of microbial ecosystems. The stable states of microbial communities are commonly perceived as static and, thus, have not been extensively examined. The present study investigated stabilizing mechanisms, minority functions, and the reliability of quantitative ana-lyses, emphasizing a metabolic network perspective. A bacterial community, formed by batch transferred cultures supplied with phenol as the sole carbon and energy source and paddy soil as the inoculum, was analyzed using a principal coordinate ana-lysis (PCoA), mathematical models, and quantitative parameters defined as growth activity, community-changing activity, community-forming activity, vulnerable force, and resilience force depending on changes in the abundance of operational taxonomic units (OTUs) using 16S rRNA gene amplicon sequences. PCoA showed succession states until the 3rd transferred cultures and stable states from the 5th to 10th transferred cultures. Quantitative parameters indicated that the bacterial community was dynamic irrespective of the succession and stable states. Three activities fluctuated under stable states. Vulnerable and resilience forces were detected under the succession and stable states, respectively. Mathematical models indicated the construction of metabolic networks, suggesting the stabilizing mechanism of the community structure. Thirteen OTUs coexisted during stable states, and were recognized as core OTUs consisting of majorities, middle-class, and minorities. The abundance of the middle-class changed, whereas that of the others did not, which indicated that core OTUs maintained metabolic networks. Some extremely low abundance OTUs were consistently exchanged, suggesting a role for scavengers. These results indicate that stable states were formed by dynamic metabolic networks with members functioning to achieve robustness and plasticity.

Enhanced granulation of activated sludge in an airlift reactor for organic carbon removal and ammonia retention from industrial fermentation wastewater: A comparative study.

Ammonia retention and recovery from high-nitrogenous wastewater are new concepts being used for nitrogen management. A microaerophilic activated sludge system was developed to convert organic nitrogen into ammonia and retain it for its recovery; however, the settleability of activated sludge remains a challenge. Therefore, this study proposed an aerobic granular sludge system as a potential solution. Two types of sequencing batch reactors-airlift and upflow reactors-were operated to investigate the feasibility of fast granule formation, the performance of organic carbon removal and ammonia retention, and the dynamics of microbial community composition. The operation fed with industrial fermentation wastewater demonstrated that the airlift reactor ensured a more rapid granule formation than the upflow reactor because of the high shear force, and it maintained a superior ammonia retention stability of approximately 85 %. Throughout the operational period, changes in hydraulic retention time (HRT), settling time, and exchange ratio altered the granular particle sizes and microbial community compositions. Rhodocyclaceae were replaced with Comamonadaceae, Methylophilaceae, Xanthomonadaceae, and Chitinophagaceae as core taxa instrumental in granulation, likely because of their extracellular polymeric substance secretion. As the granulation process progressed, a significant decrease in the relative abundances of nitrifying bacteria-Nitrospiraceae and Nitrosomonadaceae-was observed. The reduction of settling time and HRT enhanced granulation and inhibited the activity of nitrifying bacteria. The success in granulation for ammonia conversion and retention in this study accelerates the paradigm shift from ammonia removal to ammonia recovery from industrial fermentation wastewater.

Anti-biofouling performance and microbial communities of an integrated fixed-film activated sludge membrane bioreactor with a fibrous carrier material: Pilot-scale demonstration.

Widespread use of membrane bioreactors for high-performance wastewater treatment depends on the prevention of biofouling during membrane filtration, which can reduce operating costs. Biofouling is usually prevented using mechanical and chemical membrane treatment methods, which can be time-consuming and expensive. In this study, we developed bio-capsules as a fluidizing carrier material in an integrated fixed-film activated sludge membrane bioreactor (IFAS-MBR). The bio-capsules were prepared from moniliform polyvinylidene chloride fibrous balls enclosed in a spherical plastic basket, and could harbor protozoa and metazoa. A pilot-scale anoxic-oxic IFAS-MBR system with a total volume of 132 m3 was operated to remove organic carbon and nitrogen from municipal wastewater at a high permeate flux (0.84 m3/m2/day). The efficacy of the bio-capsules and the prokaryotic/eukaryotic community structures in the system were investigated. After operation for 1 year, the system demonstrated stable removal of organic carbon (76.0 % ± 15.5 % as total organic carbon, 93.1 ± 5.3 % as BOD, and 88.5 ± 5.2 % as CODMn) and nitrogen (71.3 % ± 9.3 %) despite fluctuations in the influent concentrations. Increases in transmembrane pressure (TMP) were retarded from its increase rates from 0.56 kPa/day to 0.149-0.224 kPa/day by the bio-capsules, and the TMP was kept constant at around 20 kPa throughout the operational period. High-throughput sequencing of 16S rRNA gene amplicons showed that the prokaryotic family Pirellulaceae was metabolically active and correlated with the TMP. According to the 18S rRNA gene sequencing, the eukaryotic metazoan Bdelloidea was more abundant in the bio-capsules than in activated sludge, which was supported by microscopic observations. These results suggest that the application of bio-capsules prevents increases in the TMP by harboring the procaryotes and eukaryotes responsible for biofouling mitigation in the IFAS-MBR system.

Methane diffusion affects characteristics of benthic communities in and around microbial mat-covered sediments in the northeastern Japan sea.

We investigated relationships between features of benthic macrofaunal communities and geochemical parameters in and around microbial mat-covered sediments associated with a methane seepage on Sakata Knoll in the eastern Japan Sea. A depression on top of the knoll corresponds to a gas-hydrate-bearing area with seepage of methane-rich fluid, and microbial mats cover the seafloor sediments. Sediment cores were collected at three sites for this study: one within a microbial mat, a second a few meters outside of the microbial mat, and a third from a reference site outside the gas-hydrate-bearing areas. Morphological analysis showed that the site inside the microbial mat had higher macrofaunal density and biomass compared with the other sites. 18S rRNA gene analysis showed that annelids were dominant in the surface sediment inside the microbial mat with the possible occurrence of microbial anaerobic oxidation of methane (AOM), whereas in the surface sediments outside the microbial mat and at the reference site the predominant species belonged to phylum Cercozoa. Morphological analysis also showed that the surface sediment inside the microbial mat noticeably favored annelids, with dorvilleid Ophryotrocha sp. and ampharetid Neosabellides sp. identified as major constituents. Statistical analysis showed that sulfidic sediment conditions with concentrations of H2S up to 121 µM resulting from AOM likely resulted in the predominance of annelids with tolerance to sulfide. Both the 18S rRNA genes and macrofaunal characteristics showed that benthic biodiversity among the three sites was greatest outside the microbial mat. The site outside the microbial mat may represent geochemical transition conditions, including a lower rate of upward methane gas-flow compared with the site inside the microbial mat. The high biodiversity there might result from the presence of species specifically suited to the transition zone as well as species also found in photosynthesis-based communities of the background environment.

Evaluation of nitrous oxide emission during ammonia retention from simulated industrial wastewater by microaerobic activated sludge process.

Considering the reciprocating processes of nitrogen gas (N2) fixation to ammonia (NH4-N) and NH4-N removal to N2 through nitrification and denitrification during wastewater treatment, a microaerobic activated sludge process (MAS) is proposed in this study as a pretreatment to retain NH4-N from high-strength nitrogenous wastewater for further NH4-N recovery through membrane technology, that is, inhibit nitrification, with sufficient removal of total organic carbon (TOC). With DO and pH control, the 3-reactor bench-scale MAS systems successfully realized an NH4-N retention rate of over 80 %, with TOC removal rates of over 90 %. In addition, the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) during MAS were evaluated. The total N2O emissions were 407 and 475 mg-N/day when pH was controlled at 6.2 (S1) and 6.8 (S2), respectively, with average emission factors to total nitrogen load over 2 % in both systems. Also, the global warming potential of N2O is one order of magnitude larger than that of CO2, indicating the significance of N2O in the MAS process. Therefore, the mechanisms of N2O emission from each reactor were investigated. The first reactor, where most of the TOC was adsorbed, emitted only 1.98 % (S1) and 2.43 % (S2) of the total N2O emissions through the denitrification of nitrite and nitrate (NOx) from the return sludge. The second reactor emitted 79.9 % (S1) and 69.0 % (S2) of the total N2O with the emission rates the same order of magnitude as the NOx production rates. Multiple pathways were considered to contribute to the high N2O emissions, and biotic NH2OH oxidation was one potential pathway at pH 6.2. Finally, the third reactor emitted 9.98 % (S1) and 16.8 % (S2) of the total N2O by nitrifier denitrification. Overall, this study showed that the large N2O emissions under nitrification-inhibiting conditions of the MAS process owed to the incomplete nitrification under acidic conditions and large abundances of denitrifiers. On the other hand, the lower N2O emissions at pH 6.2 evidenced the potential N2O mitigation under slightly more acidic conditions, underlining the necessity of further study on N2O mitigation when adapting to the trend of NH4-N recovery.

Hybrid osmotically assisted reverse osmosis and reverse osmosis (OARO-RO) process for minimal liquid discharge of high strength nitrogenous wastewater and enrichment of ammoniacal nitrogen.

Ammoniacal nitrogen (NH4N) is a ubiquitous nitrogen pollutant found in wastewater, which could cause eutrophication and severe environmental stress. It is therefore necessary to manage NH4N by enrichment and recovery for potential reuse, as well as to regulate the amount of environmental discharge. Hybridization of membrane-based processes is an attractive option for further enhancing water and nutrient reclamation from waste streams; thus, in this present work, a hybrid osmotically assisted reverse osmosis (OARO) and reverse osmosis (RO) process was demonstrated for subsequent ammoniacal nitrogen enrichment and wastewater discharge management. Using a commercially-available cellulose triacetate membrane module, model and real wastewater containing approximately 4,000ppm NH4N were effectively dewatered and enriched to a final NH4N content of 40,300ppm. This corresponds to enrichment of around 10 times and approximately 90% pure water recovery. The effective combination of both processes resulted in high efficiency, as well as economical and energy-saving benefits, as shown by the process performance and our preliminary techno-economic analysis. The specific energy consumption of the hybrid process projected to operate at a capacity of 2,000 m3h-1 was determined to be 8.8kWh m-3, or 0.56kWh kg-1 NH4Cl removed/recovered for an initial feed solution containing around 15,300ppm NH4Cl. Hybrid OARO and RO operation was able to achieve satisfactory enrichment by the OARO process and obtaining clean water by the RO process. The hybrid OARO-RO process has shown great potential as a suitable end-stage membrane-based process for wastewater dewatering and NH4N enrichment and recovery toward a circular economy and environmental management, as well as clean water recovery.

Microaerophilic Activated Sludge System for Ammonia Retention toward Recovery from High-Strength Nitrogenous Wastewater: Performance and Microbial Communities.

A transition to ammonia recovery from wastewater has started; however, a technology for sustainable nitrogen retention in the form of ammonia and organic carbon removal is still in development. This study validated a microaerophilic activated sludge (MAS) system to efficiently retain ammonia from high-strength nitrogenous wastewater. The MAS is based on conventional activated sludge (CAS) with aerobic and settling compartments. Low dissolved oxygen (DO) concentrations (<0.2 mg/L) and short solids retention times (SRTs) (<5 days) eliminated nitrifying bacteria. The two parallel MASs were successfully operated for 300 days and had ammonia retention of 101.7 ± 24.9% and organic carbon removal of 85.5 ± 8.9%. The MASs mitigated N2O emissions with an emission factor of <0.23%, much lower than the default value of CAS (1.6%). A short-term step-change test demonstrated that N2O indicated the initiation of nitrification and the completion of denitrification in the MAS. The parallel MASs had comparable microbial diversity, promoting organic carbon oxidation while inhibiting ammonia-oxidizing microorganisms (AOMs), as revealed by 16S rRNA gene amplicon sequencing, the quantitative polymerase chain reaction of functional genes, and fluorescence in situ hybridization of ß-proteobacteria AOB. The microbial analyses also uncovered that filamentous bacteria were positively correlated with effluent turbidity. Together, controlling DO and SRT achieved organic carbon removal and successful ammonia retention, mainly by suppressing AOM activity. This process represents a new nitrogen management paradigm.

Metabolic implications for predatory and parasitic bacterial lineages in activated sludge wastewater treatment systems.

Deciphering unclear microbial interactions is key to improving biological wastewater treatment processes. Microbial predation and parasitism in wastewater treatment ecosystems are unexplored survival strategies that have long been known and have recently attracted attention because these interspecies interactions may contribute to the reduction of excess sludge. Here, microbial community profiling of 600 activated sludge samples taken from six industrial and one municipal wastewater treatment processes (WWTPs) was conducted. To identify the shared lineages in the WWTPs, the shared microbial constituents were defined as the family level taxa that had ≥ 0.1% average relative abundance and detected in all processes. The microbial community analysis assigned 106 families as the shared microbial constituents in the WWTPs. Correlation analysis showed that 98 of the 106 shared families were significantly correlated with total carbon (TC) and/or total nitrogen (TN) concentrations, suggesting that they may contribute to wastewater remediation. Most possible predatory or parasitic bacteria belonging to the phyla Bdellovibrionota, Myxococcota, and Candidatus Patescibacteria were found to be the shared families and negatively correlated with TC/TN; thus, they were frequently present in the WWTPs and could be involved in the removal of carbon/nitrogen derived from cell components. Shotgun metagenome-resolved metabolic reconstructions indicated that gene homologs associated with predation or parasitism are conserved in the Bdellovibrionota, Myxococcota, and Ca. Patescibacteria genomes (e.g., host interaction (hit) locus, Tad-like secretion complexes, and type IV pilus assembly proteins). This study provides insights into the complex microbial interactions potentially linked to the reduction of excess sludge biomass in these processes.

Startup performance and microbial composition of a pilot-scale rapid sand filter for the treatment of manganese-containing mine water.

The inexpensive removal of soluble manganese [Mn(II)] from mine water that contains large quantities of Mn(II) should be prioritized given that large quantities of alkaline reagents are typically used in the chemical treatment of Mn-rich water from abandoned mines. Rapid sand filter (RSF) systems are widely used as a cost-effective technology in drinking water treatment processes to remove iron and Mn from groundwater. Here, we applied a pilot-scale RSF to treat mine water with a neutral pH and containing approximately 22 mg/L of Mn(II). Following a lag phase from its startup (day 1-day 26), Mn removal rates increased to approximately 40% for around 1 month (day 27-day 55) without the use of alkaline reagents but did not increase during further operation. Quantitative elemental analysis revealed Mn oxides on the sand filters during the Mn removal period. The bacterial communities on the RSFs, recorded on day 42 and day 85, were characterized and compared using 16S rRNA gene amplicon sequencing. Although the well-known Mn-oxidizing bacteria (MOB) were not listed among the ten most dominant operational taxonomic units (OTUs) on the sand filters (relative abundances: >0.68%), a significant increase in the OTUs related to well-known alphaproteobacterial MOB, such as Pedomicrobium spp., were observed during the period.

Microbially produced fertilizer provides rhizobacteria to hydroponic tomato roots by forming beneficial biofilms.

Hydroponic cultivation of Solanum lycopersicum (tomato) is important, and high tomato production depends on the use of nitrogen and phosphate fertilizers. We had developed a microbial fertilizer (MF), which is mainly composed of nitrate. To investigate the effect of MF on plant growth, hydroponic tomato was grown with MF or commercial inorganic fertilizer (IF), and the microbiomes of the rhizosphere and the liquid phase were analyzed by confocal microscopy and high-throughput sequencing. Plant biomass and biofilm formation were increased by growth in MF compared to IF. The microbial community structures of tomato roots and hydroponic water differed between the two conditions, and three operational taxonomic units (OTUs) dominated in plants grown with MF. The three OTUs were related to Rudaea spp., Chitinophaga spp., and Stenotrophobacter terrae, which are reported to be disease-suppressive epiphytic or endophytic microbes of plant roots. Because these three OTUs also predominated in the MF itself, they were likely provided to the rhizosphere or endophytic environments of tomato roots via hydroponic water. KEY POINTS: • Microbial fertilizer for hydroponic growth enhanced biofilm formation on tomato root. • Microbial fertilizer contains tomato-root epiphytic or endophytic microbes. • Microbial fertilizer provided beneficial microbes to the rhizosphere and endophytic environments of tomato roots via hydroponic water.

Microscopic evidence of sandstone deterioration and damage by fungi isolated from the Angkor monuments in simulation experiments.

The Angkor monuments have been registered on the World Cultural Heritage List of UNESCO, while the buildings built mostly of sandstone are suffering from serious deterioration and damage. Microorganisms are one of the leading causes for the sandstone deterioration. Identification of the mechanisms underlying the biodeterioration is of significance because it reveals the biochemical reaction involved so that effective conservation and restoration of cultural properties can be achieved. In this study, the fungal colonization and biodeterioration of sandstone in simulation experiments were examined using confocal reflection microscopy (CRM) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). Aspergillus sp. strain AW1 and Paecilomyces sp. strain BY8 isolated from the deteriorated sandstone of Angkor Wat and Bayon of Angkor Thom, respectively, were inoculated and incubated with the sandstone used for construction of Angkor Wat. With CRM, we could visualize that strain AW1 tightly attached to and broke in the sandstone with extension of the hyphae. Quantitative imaging analyses showed that the sandstone surface roughness increased and the cavities formed under the fungal hyphae deepened during the incubation of strains AW1 and BY8. These highlighted that the massive growth of fungi even under the culture conditions was associated with the cavity formation of the sandstone and its expansion. Furthermore, SEM-EDS indicated the flat and Si-rich materials, presumably quartz and feldspar, were found frequently at the intact sandstone surface. But the flatness was lost during the incubation, possibly due to the detachment of the Si-rich mineral particles by the fungal deterioration. Consequently, this study proposed a biodeterioration model of the sandstone in that the hyphae of fungi elongated on the surface of the sandstone to penetrate into the soft and porous sandstone matrix, damaging the matrix and gradually destabilize the hard and Si-rich minerals, such as quartz and feldspar, to the collapse and cavities.

Evaluating the Optimal Oil Concentrations in the Startup Performance of a Membrane Bioreactor Treating Oily Noodle-soup Wastewater.

The discharge of high-strength oily wastewater adversely affects the environment; therefore, the treatment of wastewater containing fats, oils, and grease from the food industry is of importance. In this study, we used a membrane bioreactor (MBR) to treat Ramen noodle-soup wastewater, and we evaluated the optimal oil concentration in the wastewater for the startup of the MBR treatment in winter and summer. The MBR system had a sufficient startup in both seasons when fed with a 20-fold dilution of the original oily wastewater, containing approximately 950 to 1,200 mg/L oil and approximately 3,000 to 4,400 mg/L biological oxygen demand (BOD; BOD-SS load of 0.1 to 0.2 kg/kg/d). The reactor performance in winter were relatively stable during the operation. While, activated sludge microbes in summer were not highly active with a 40-fold dilution of wastewater, because of the decreased mixed liquor suspended solid concentration during the operation period. Population shifts in the sludge microbiome with increasing oil concentrations were analyzed using high-throughput sequencing, and the relative abundance of operational taxonomic units belonging to the phylum Bacteroidetes were highest in both winter and summer when fed with 20-fold dilution of the wastewater. In particular, the family Chitinophagaceae was dominant, with relative abundances of 13.5% in winter and 5.1% in summer, suggesting that this family may play important roles in the startup of a MBR treating the wastewater.

Evaluation of dye decolorization using anaerobic granular sludge from an expanded granular sludge bed based on spectrometric and microbiome analyses.

The decolorization of 11 dyes by granular sludge from an anaerobic expanded granular sludge bed (EGSB) reactor was evaluated. Biological decolorization of Reactive Red 21, 23, and 180, and Reactive Yellow 15, 17, and 23 in model textile wastewater was observed for the first time after a 7-day incubation (over 94% decolorization). According to the sequencing analysis of 16S rRNA gene amplicons from EGSB granular sludge, the operational taxonomic unit related to Paludibacter propionicigenes showed the highest increase in relative abundance ratios in the presence of dyes (7.12 times on average over 11 dyes) compared to those without dyes.

Low nitrous oxide concentration and spatial microbial community transition across an urban river affected by treated sewage.

Urban rivers receive used water derived from anthropogenic activities and are a crucial source of the potent greenhouse gas nitrous oxide (N2O). However, considerable uncertainties still exist regarding the variation and mechanisms of N2O production in response to the discharge of treated sewage from municipal wastewater treatment plants (WWTPs). This study investigated N2O concentrations and microbial processes responsible for nitrogen conversion upstream and downstream of WWTPs along the Tama River flowing through Tokyo, Japan. We evaluated the effect of treated sewage on dissolved N2O concentrations and inherent N2O consumption activities in the river sediments. In summer and winter, the mean dissolved N2O concentrations were 0.67 µg-N L-1 and 0.82 µg-N L-1, respectively. Although the dissolved N2O was supersaturated (mean 288.7% in summer, mean 240.7% in winter) in the river, the N2O emission factors (EF5r, 0.013%-0.025%) were significantly lower than those in other urban rivers and the Intergovernmental Panel on Climate Change default value (0.25%). The nitrate (NO3-) concentration in the Tama River increased downstream of the WWTPs discharge sites, and it was the main nitrogen constituent. An increasing trend of NO3- concentration was observed from upstream to downstream, along with an increase in the N2O consumption potential of the river sediment. A multiple regression model showed that NO3- is the crucial factor influencing N2O saturation. The diversity in the upstream microbial communities was greater than that in the downstream ones, indicating the involvement of treated sewage discharge in shaping the microbial communities. Functional gene quantification for N2O production and consumption suggested that nirK-type denitrifiers likely contributed to N2O production. Structural equation models (SEMs) revealed that treated sewage discharged from WWTPs increased the NO3- loading from upstream to downstream in the river, inducing changes in the microbial communities and enhancing the N2O consumption activities. Collectively, aerobic conditions limited denitrification and in turn facilitated nitrification, leading to low N2O emissions even despite high NO3- loadings in the Tama River. Our findings unravel an overestimation of the N2O emission potential in an urban oxygen-rich river affected by treated sewage discharge.

Draft Genome Sequences of Sulfurovum spp. TSL1 and TSL6, Two Sulfur-Oxidizing Bacteria Isolated from Marine Sediment.

Sulfurovum spp. TSL1 and TSL6 are sulfur-oxidizing chemolithoautotrophic bacteria isolated from the tsunami-launched marine sediment in the Great East Japan earthquake. This announcement describes the draft genome sequences of the two isolates that possess the gene sets for the sulfur oxidation pathway.

Optimal start-up conditions for the efficient treatment of acid mine drainage using sulfate-reducing bioreactors based on physicochemical and microbiome analyses.

Typically, sulfate-reducing bioreactors used to treat acid mine drainage (AMD) undergo an initial incubation period of a few weeks to acclimatize sulfate-reducing bacteria (SRB), although necessity of this preincubation has rarely been evaluated. To reduce time and economic cost, we developed an SRB acclimatization method using the continuous flow of AMD into bioreactors fed with rice bran, and compared with the conventional acclimatization method. We found that the SRB sufficiently acclimatized without the preincubation phase. Furthermore, we examined the performance and SRB communities in bioreactors operated for >200 days under seven different conditions, in which the amount of rice bran added and hydraulic retention times (HRTs) were varied. A comparison of the various bioreactor conditions revealed that the lowest rice bran amount (50 g) and the shortest HRT (6 h) caused a deterioration in reactor performance after day 144 and 229, respectively. In both cases, relatively aerobic environments developed due to the lack of organic matter seemed to inhibit sulfate reduction. Of the conditions tested, operation of the bioreactors with 200 g of rice bran and an HRT of 12.5 h was the most effective in treating AMD, showing a sulfate reduction rate of 20.7-77.9% during days 54-242. DATA AND MATERIALS AVAILABILITY: All data needed to evaluate the conclusions of this study are presented in the paper and/or the appendix.

Draft Genome Sequences of the Ferric Iron-Reducing Geobacter sp. Strains AOG1 and AOG2, Isolated from Enrichment Cultures on Crystalline Iron(III) Oxides.

Here, we report the draft genome sequences of two Geobacter sp. strains, AOG1 and AOG2, isolated from enrichment cultures using crystalline Fe(III) oxides as electron acceptors. Strains AOG1 and AOG2 possess numerous genes encoding multiheme c-type cytochromes and pilA-N genes encoding the pilin monomer of nanowires in their genomes.

Insecticide resistance by a host-symbiont reciprocal detoxification.

Insecticide resistance is one of the most serious problems in contemporary agriculture and public health. Although recent studies revealed that insect gut symbionts contribute to resistance, the symbiont-mediated detoxification process remains unclear. Here we report the in vivo detoxification process of an organophosphorus insecticide, fenitrothion, in the bean bug Riptortus pedestris. Using transcriptomics and reverse genetics, we reveal that gut symbiotic bacteria degrade this insecticide through a horizontally acquired insecticide-degrading enzyme into the non-insecticidal but bactericidal compound 3-methyl-4-nitrophenol, which is subsequently excreted by the host insect. This integrated "host-symbiont reciprocal detoxification relay" enables the simultaneous maintenance of symbiosis and efficient insecticide degradation. We also find that the symbiont-mediated detoxification process is analogous to the insect genome-encoded fenitrothion detoxification system present in other insects. Our findings highlight the capacity of symbiosis, combined with horizontal gene transfer in the environment, as a powerful strategy for an insect to instantly eliminate a toxic chemical compound, which could play a critical role in the human-pest arms race.