Burkholderiaceae Are Key Acetate Assimilators During Complete Denitrification in Acidic Cryoturbated Peat Circles of the Arctic Tundra

Baseflow and Coupled Nitrification-Denitrification Processes Jointly Dominate Nitrate Dynamics in a Watershed Impacted by Rare Earth Mining

Mining activities cause severe nitrogen pollution in watersheds, yet our understanding of the transport pathways, transformation processes, and control mechanisms of nitrate (NO3-) in these areas is limited. Based on nearly 4-year observations of groundwater and river in China's largest ion-adsorption rare earth mining watershed, we revealed the dynamics of NO3- and its drivers using stoichiometry-based load model, molecular biological, and multi-isotope approaches. Results indicated that the NO3- dynamics were jointly controlled by sources (precipitation, terrestrial inputs, and sediment supply) and processes (hydrological and biological). The monthly NO3- export load from the 444.4 km2 watershed was 3.72 × 105 kg. Groundwater (36 ± 26%) and soil nitrogen (25 ± 17%) were the primary exogenous sources of NO3-. Baseflow was the main hydrological pathway for legacy nitrogen into the river, contributing 66.8% of the NO3- load. Coupled nitrification-denitrification were key biological processes affecting the NO3- transformation, with denitrification contributing 58%. Burkholderia were most associated with NO3- transformation. Dissolved organic carbon and oxygen were major drivers affecting the NO3- production and consumption. This study highlights effective control and management strategies for nitrogen pollution in mining-affected watersheds, considering not only reducing nitrogen inputs but also integrating hydrological pathways and nitrogen transformation mechanisms.

Diversity of microbial, biocontrol agents and nematode abundance on a susceptible Prunus rootstock under a Meloidogyne root gradient infection

Root-knot nematodes (RKNs) of the genus Meloidogyne are one of the most damaging genera to cultivated woody plants with a worldwide distribution. The knowledge of the soil and rhizosphere microbiota of almonds infested with Meloidogyne could help to establish new sustainable and efficient management strategies. However, the soil microbiota interaction in deciduous woody plants infected with RKNs is scarcely studied. This research was carried out in six commercial almond groves located in southern Spain and infested with different levels of Meloidogyne spp. within each grove. Several parameters were measured: nematode assemblages, levels and biocontrol agents in Meloidogyne's eggs, levels of specific biocontrol agents in rhizoplane and soil, levels of bacteria and fungi in rhizoplane and soil, fungal and bacterial communities by high-throughput sequencing of internal transcribed spacer (ITS), and 16S rRNA gene in soil and rhizosphere of the susceptible almond hybrid rootstock GF-677 infested with Meloidogyne spp. The studied almond groves showed soil degradation by nematode assemblies and fungi:bacterial ratio. Fungal parasites of Meloidogyne eggs were found in 56.25% of the samples. However, the percentage of parasitized eggs by fungi ranged from 1% to 8%. Three fungal species were isolated from Meloidogyne eggs, specifically Pochonia chlamydosporia, Purpureocillium lilacinum, and Trichoderma asperellum. The diversity and composition of the microbial communities were more affected by the sample type (soil vs rhizosphere) and by the geographical location of the samples than by the Meloidogyne density, which could be explained by the vigorous hybrid rootstock GF-677 and a possible dilution effect. However, the saprotrophic function in the functional guilds of the fungal ASV was increased in the highly infected roots vs the low infected roots. These results indicate that the presence of biocontrol agents in almond fields and the development of new management strategies could increase their populations to control partially RKN infection levels.

Hybrid constructed wetlands and filamentous fungi for treatment of mixed sewage and industrial effluents

Developing countries face multifaceted problems of water pollution and futile measures to combat water pollution. This study was conducted to explore the potential application of sustainable nature-based solutions, hybrid constructed wetlands, and the application of filamentous fungi to treat polluted river water that receives sewage and industrial wastewater. A pilot-scale hybrid constructed wetland design comprising two types of floating plants in distinct tanks along with a floating wetland and a free-water surface wetland connected in series was commissioned and tested. The system successfully removed organic pollution (BOD 94% and COD 90%), nutrients (NH4-N and NO3-N 67% and PO4-P 81%), and heavy metals (Cr 75%, Ni 56%, and Fe 79%) in 40 h and showed a high buffering capacity to cope with the varying pollutant loads. Metagenomics analysis of treated and untreated samples of river water revealed a diversified spatial bacterial community with ~ 25% sequences related to sulfur-metabolizing bacteria, genus Sulfuricurvum. The application of an immobilized strain of A. niger as a mycoremediation technique was also tested. It successfully removed pollutants in the combined sewage and industrial wastewater present in river water: COD (96%), TSS (97%), NH4-N (65%), NO3-N (67%), and PO4-P (78%). This study demonstrated that hybrid constructed wetlands and mycoremediation can be used as sustainable wastewater treatment options in the local context and also in developing countries where most of the conventional wastewater treatment plants do not operate.

Using RNA-Stable isotope probing to investigate methane oxidation metabolites and active microbial communities in methane oxidation coupled to denitrification

The active denitrifying communities performing methane oxidation coupled to denitrification (MOD) were investigated using samples from an aerobic reactor (∼20% O2 and 2% CH4) and a microaerobic reactor (2% O2, 2% CH4) undertaking denitrification. The methane oxidation metabolites excreted in the reactors were acetate, methanol, formate and acetaldehyde. Using anaerobic batch experiments supplemented with exogenously supplied 13C-labelled metabolites, the active denitrifying bacteria were identified using 16S rRNA amplicon sequencing and RNA-stable isotope probing (RNA-SIP). With the aerobic reactor (AR) samples, the maximum NO3- removal rates were 0.43 mmol g-1 d-1, 0.40 mmol g-1 d-1, 0.33 mmol g-1 d-1 and 0.10 mmol g-1 d-1 for exogenously supplied acetate, formate, acetaldehyde and methanol batch treatments respectively, while with the microaerobic reactor (MR) samples, the maximum NO3- removal rates were 0.41 mmol g-1 d-1, 0.33 mmol g-1 d-1, 0.38 mmol g-1 d-1 and 0.14 mmol g-1 d-1 for exogenously supplied acetate, formate, acetaldehyde and methanol batch treatments respectively. The RNA-SIP experiments with 13C-labelled acetate, formate, and methanol identified Methyloversatilis, and Hyphomicrobium as the active methane-driven denitrifying bacteria in the AR samples, while Pseudoxanthomonas, Hydrogenophaga and Hyphomicrobium were the active MOD bacteria in the MR samples. Collectively, all the data indicate that formate is a key cross-feeding metabolite excreted by methanotrophs and consumed by denitrifiers performing MOD.

Downflow sponge biofilm reactors for polluted raw water treatment: Performance optimisation, kinetics, and microbial community

Water outages caused by elevated ammonium (NH4+-N) levels are a prevalent problem faced by conventional raw water treatment plants in developing countries. A treatment solution requires a short hydraulic retention time (HRT) to overcome nitrification rate limitation in oligotrophic conditions. In this study, the performance of polluted raw water treatment using a green downflow sponge biofilm (DSB) technology was evaluated. We operated two DSB reactors, DSB-1 and DSB-2 under different NH4+-N concentration ranges (DSB-1: 3.2-5.0 mg L-1; DSB-2: 1.7-2.6 mg L-1) over 360 days and monitored their performance under short HRT (60 min, 30 min, 20 min, and 15 min). The experimental results revealed vertical segregation of organic removal in the upper reactor depths and nitrification in the lower depths. Under the shortest HRT of 15 min, both DSB reactors achieved stable NH4+-N and chemical oxygen demand removal (≥95%) and produced minimal effluent nitrite (NO2--N). DSB system could facilitate complete NH4+-N oxidation to nitrate (NO3--N) without external aeration energy requirement. The 16S rRNA sequencing data revealed that nitrifying bacteria Nitrosomonas and Nitrospira in the reactor were stratified. Putative comammox bacteria with high ammonia affinity was successfully enriched in DSB-2 operating at a lower NH4+-N loading rate, which is advantageous in oligotrophic treatment. This study suggests that a high hydraulic rate DSB system with efficient ammonia removal could incorporate ammonia treatment capability into polluted raw water treatment process and ensure safe water supply in many developing countries.

Anaerobic methane oxidation is quantitatively important in deeper peat layers of boreal peatlands: Evidence from anaerobic incubations, in situ stable isotopes depth profiles, and microbial communities

Boreal peatlands store most of their carbon in layers deeper than 0.5 m under anaerobic conditions, where carbon dioxide and methane are produced as terminal products of organic matter degradation. Since the global warming potential of methane is much greater than that of carbon dioxide, the balance between the production rates of these gases is important for future climate predictions. Herein, we aimed to understand whether anaerobic methane oxidation (AMO) could explain the high CO2/CH4 anaerobic production ratios that are widely observed for the deeper peat layers of boreal peatlands. Furthermore, we quantified the metabolic pathways of methanogenesis to examine whether hydrogenotrophic methanogenesis is a dominant methane production pathway for the presumably recalcitrant deeper peat. To assess the CH4 cycling in deeper peat, we combined laboratory anaerobic incubations with a pathway-specific inhibitor, in situ depth patterns of stable isotopes in CH4, and 16S rRNA gene amplicon sequencing for three representative boreal peatlands in Western Siberia. We found up to a 69 % reduction in CH4 production due to AMO, which largely explained the high CO2/CH4 anaerobic production ratios and the in situ depth-related patterns of δ13C and δD in methane. The absence of acetate accumulation after inhibiting acetotrophic methanogenesis and the presence of sulfate- and nitrate-reducing anaerobic acetate oxidizers in the deeper peat indicated that these microorganisms use SO42- and NO3- as electron acceptors. Acetotrophic methanogenesis dominated net CH4 production in the deeper peat, accounting for 81 ± 13 %. Overall, anaerobic oxidation is quantitatively important for the methane cycle in the deeper layers of boreal peatlands, affecting both methane and its main precursor concentrations.

Nano manganese dioxide coupling carbon source preloading granular activated carbon biofilter enhancing biofilm formation and pollutant removal

The formation of stable and mature biofilms affects the efficient and stable removal of ammonium by biological activated carbon (BAC). In this study, the new granular activated carbon (GAC) was preloaded with the carbon source (glucose and sucrose) and nano manganese dioxide (nMnO2) before using. Then tests were performed to determine whether substrate preloading promoted ammonium removal. The ammonium removal treated by nMnO2 coupled with sucrose-loaded BAC reached 49.1 ± 2.5%, which was 1.7 times higher than that by the nonloaded BAC 28.2 ± 1.9%). The biomass on the substrate-loaded BAC reached 5.83 × 106-1.22 × 107 cells/g DW GAC on Day 7, which was 4.6-9.5 times higher than the value of the nonloaded BAC (1.28 × 106 cells/g DW GAC). The amount of extracellular polymer (i.e., protein) on nMnO2 coupled to sucrose-loaded BAC was promoted significantly. Flavobacterium (0.7%-11%), Burkholderiaceae (13%-20%) and Aquabacterium (30%-67%) were the dominant functional bacteria on the substrate-loaded BAC, which were conducive to the nitrification or denitrification process. The results indicated that loading nMnO2 and/or a carbon source accelerated the formation of biofilms on BAC and ammonium removal. Additionally, the ammonium removal treated by nMnO2 coupled with sucrose-loaded BAC was contributed by microbial degradation (56.0 ± 2.5%), biofilm adsorption (38.7 ± 2.1%) and GAC adsorption (5.3 ± 0.3%), suggesting a major role of microbial degradation.

Stable isotope probing reveals compositional and functional shifts in active denitrifying communities along the soil profile in an intensive agricultural area

Denitrifying microbial communities in the vadose zone play an essential role in eliminating the nitrate leached from agricultural practices. This nitrate could otherwise contaminate groundwater and threaten public health. Here, we utilized stable isotope probing combined with amplicon sequencing and functional gene quantification to inspect the composition and function of heterotrophic denitrifying microorganisms along a 9-m soil profile in an intensive agricultural area. Dramatic differences in the composition of the active denitrifiers were uncovered between the surface soil and deep layers of the vadose zone. The main denitrifying bacterial taxa identified from 13C-DNA fractions were Pseudomonadaceae (Pseudomonas), Rhodocyclaceae (Azoarcus), and Burkholderiaceae in the surface soil (0-0.2 m), and were Pseudomonadaceae (Pseudomonas), Burkholderiaceae, Bacillaceae (Bacillus), and Paenibacillaceae (Ammoniphilus) in the deep layers (0.5-9.0 m). Analysis of the functional genes (nirS, nirK, and nosZ) in isotope-labeled DNA revealed an upward nos/nir ratio with increasing soil depth, which may account for the higher nitrous oxide emission potential in the surface soil, as compared to the deeper sand-rich, low organic carbon layers. This study improves our understanding of active denitrifying microbes in the vadose zone and helps in developing techniques to reduce nitrate pollution in groundwater.

Effects of zinc ion concentrations on the performance of SBR treating livestock wastewater and analysis of microbial community

Zinc ion (Zn2+) is a frequently occurring heavy metal in livestock wastewater. The effects of Zn2+ on the physicochemical properties and the microbial distribution of activated sludge are essential to controlling nitrogen removal performance. Nevertheless, there are raw studies on the effects of Zn2+ on nitrogen removal. This study investigated the effect of Zn2+ on the treatment performance of livestock wastewater in a sequencing batch reactor (SBR). The results indicated the low Zn2+ concentrations could improve nitrogen removal performance. However, as the Zn2+ concentration increased, the total nitrogen (TN) removal performance of the reactor gradually deteriorated. When the Zn2+ concentration was 90.00 mg/L, the TN removal efficiency was the lowest, only 2.40%. The contents of the Extracellular polymeric substance (EPS) presented a trend of first increasing and then decreasing with the increase of Zn2+ concentration, and the main reason was the decrease of protein-like and tryptophan-like. The 16SrRNA analysis indicated that Zn2+ within a specific concentration could increase the operational taxonomic units (OTUs) number, microbial richness, and diversity of microorganisms in the SBR. However, with Zn2+ concentration exceeding 10.00 mg/L, the relative abundance of denitrification functional bacteria (Dechloromonas, Nitrospira, and Thauera) decreased.

Deterministic Development of Soil Microbial Communities in Disturbed Soils Depends on Microbial Biomass of the Bioinoculum

Despite its enormous importance for ecosystem services, factors driving microbial recolonization of soils after disturbance are still poorly understood. Here, we compared the microbial recolonization patterns of a disturbed, autoclaved soil using different amounts of the original non-disturbed soil as inoculum. By using this approach, we manipulated microbial biomass, but did not change microbial diversity of the inoculum. We followed the development of a new soil microbiome after reinoculation over a period of 4 weeks using a molecular barcoding approach as well as qPCR. Focus was given on the assessment of bacteria and archaea. We could show that 1 week after inoculation in all inoculated treatments bacterial biomass exceeded the values from the original soil as a consequence of high dissolved organic carbon (DOC) concentrations in the disturbed soil resulting from the disturbance. This high biomass was persistent over the complete experimental period. In line with the high DOC concentrations, in the first 2 weeks of incubation, copiotrophic bacteria dominated the community, which derived from the inoculum used. Only in the disturbed control soils which did not receive a microbial inoculum, recolonization pattern differed. In contrast, archaeal biomass did not recover over the experimental period and recolonization was strongly triggered by amount of inoculated original soil added. Interestingly, the variability between replicates of the same inoculation density decreased with increasing biomass in the inoculum, indicating a deterministic development of soil microbiomes if higher numbers of cells are used for reinoculation.

Influence of nitrogen sources on wastewater treatment performance by filamentous algae in constructed wetland system

Although filamentous algae have the characteristics of high nutrient assimilation ability, and adaptation to different conditions, studies on their role in water purification of constructed wetlands (CWs) are limited. In this study, the wastewater treatment capacity under different nitrogen sources was explored by constructing a filamentous algal CW (FACW) system. Results confirmed the fast and stable operation efficiency of the FACW system. Ammonia nitrogen was preferred in Cladophora sp. absorption and assimilation. The nutrient consumption rate (NCR) for total nitrogen (TN) of AG was 2.65 mg g-1 d-1, much higher than that of nitrate nitrogen (NG) (0.89 mg g-1 d-1). The symbiosis of bacteria and Cladophora sp. Contributed to pollutant removal. A stable and diverse community of microorganisms was found on Cladophora sp. Surface, which revealed different phylogenetic relationships and functional bacterial proportions with those attached on sediment surface. In addition, temperature and light intensity have great influence on the purification ability of plants, and low hydraulic retention time is beneficial to the cost-effective operation of the system. This study provides a method to expand the utilization of wetland plants and apply large filamentous algae to the purification of wetland water quality.

Interkingdom interaction: the soil isopod Porcellio scaber stimulates the methane-driven bacterial and fungal interaction

Porcellio scaber (woodlice) are (sub-)surface-dwelling isopods, widely recognized as "soil bioengineers", modifying the edaphic properties of their habitat, and affecting carbon and nitrogen mineralization that leads to greenhouse gas emissions. Yet, the impact of soil isopods on methane-cycling processes remains unknown. Using P. scaber as a model macroinvertebrate in a microcosm study, we determined how the isopod influences methane uptake and the associated interaction network in an agricultural soil. Stable isotope probing (SIP) with 13C-methane was combined to a co-occurrence network analysis to directly link activity to the methane-oxidizing community (bacteria and fungus) involved in the trophic interaction. Compared to microcosms without the isopod, P. scaber significantly induced methane uptake, associated to a more complex bacteria-bacteria and bacteria-fungi interaction, and modified the soil nutritional status. Interestingly, 13C was transferred via the methanotrophs into the fungi, concomitant to significantly higher fungal abundance in the P. scaber-impacted soil, indicating that the fungal community utilized methane-derived substrates in the food web along with bacteria. Taken together, results showed the relevance of P. scaber in modulating methanotrophic activity with implications for bacteria-fungus interaction.

Anoxic granular activated sludge process for simultaneous removal of hazardous perchlorate and nitrate

An airtight, anoxic bubble-column sequencing batch reactor (SBR) was developed for the rapid cultivation of perchlorate (ClO₄^-) and nitrate (NO₃^-) reducing granular sludge (GS) in this study. Feast/famine conditions and shear force selection pressures in tandem with a short settling time (2-min) as a hydraulic section pressure resulted in the accelerated formation of anoxic granular activated sludge (AxGS). ClO₄^- and NO₃^- were efficiently (>99.9%) reduced over long-term (>500-d) steady-state operation. Specific NO₃^- reduction, ClO₄^- reduction, chloride production, and non-purgeable dissolved organic carbon (DOC) oxidation rates of 5.77 ± 0.54 mg NO₃^--N/g VSS·h, 8.13 ± 0^.74 mg ClO₄^-/g VSS·h, 2.40 ± 0.₄0 mg Cl^-/g VSS·h, and 16.0 ± 0.06 mg DOC/g VSS·h were recorded within the reactor under steady-state conditions, respectively. The AxGS biomass cultivated in this study exhibited faster specific ClO₄^- reduction, NO₃^- reduction, and DOC oxidation rates than flocculated biomass cultivated under similar conditions and AxGS biomass operated in an up-flow anaerobic sludge blank (UASB) bioreactor receiving the same influent loading. EPS peptide identification revealed a suite of extracellular catabolic enzymes. Dechloromonas species were present in high abundance throughout the entirety of this study. This is one of the initial studies on anoxic granulation to simultaneously treat hazardous chemicals and adds to the science of the granular activated sludge process.

Deciphering community assembly and succession in sequencing batch moving bed biofilm reactor: Differentiation between attached and suspended communities

Elucidating community assembly and succession is crucial to understanding the ecosystem functioning. Herein, the ecological processes underpinning community assembly and succession were studied to uncover the respective ecological functions of attached biofilms and suspended biomass in a sequencing batch moving bed biofilm reactor. Compared with suspended biomass, attached biofilms presented higher relative abundances of Nitrospira (2.94 %) and Nitrosomonas (1.25 %), and contributed to 66.89 ± 11.37 % and 68.11 ± 12.72 % of nitrification and denitrification activities, respectively. The microbial source tracking result demonstrated that early formation of suspended biomass was dominated by the seeding effect of detached biofilms in the start-up period (days 0-30), while self-growth of previous suspended biomass was eventually outcompeted the seeding effect when the reactor stabilized (days 31-120). Null model and ecological network analysis further suggested distinctive ecological processes underpinning the differentiation between attached and suspended communities in the same reactor. Specifically, in the start-up period, positive interactions facilitated early formation of attached (73.84 %) and suspended communities (59.41 %), while homogenous selection (88.89 %) and homogenizing dispersal (65.71 %) governed assembly of attached and suspended communities, respectively. When the reactor stabilized, attached and suspended communities showed low composition turnover as reflected by dominant homogenizing dispersal, while they presented distinctive trends of interspecies interactions. This study sheds light on discrepant ecological processes governing community differentiation of attached biofilms and suspended biomass, which would provide ecological insights into the regulation of hybrid ecosystems.

Improved Denitrification Performance of Polybutylene Succinate/Corncob Composite Carbon Source by Proper Pretreatment: Performance, Functional Genes and Microbial Community Structure

Blending biodegradable polymers with plant materials is an effective method to improve the biodegradability of solid carbon sources and save denitrification costs, but the recalcitrant lignin in plant materials hinders the microbial decomposition of available carbon sources. In the present study, corncob pretreated by different methods was used to prepare polybutylene succinate/corncob (PBS/corncob) composites for biological denitrification. The PBS/corncob composite with alkaline pretreatment achieved the optimal NO₃^--N removal rate (0.13 kg NO₃^--N m^-3 day^-1) with less adverse effects. The pretreatment degree, temperature, and their interaction distinctly impacted the nitrogen removal performance and dissolved organic carbon (DOC) release, while the N₂O emission was mainly affected by the temperature and the interaction of temperature and pretreatment degree. Microbial community analysis showed that the bacterial community was responsible for both denitrification and lignocellulose degradation, while the fungal community was primarily in charge of lignocellulose degradation. The outcomes of this study provide an effective strategy for improving the denitrification performance of composite carbon sources.

Effects of Nitrogen Input on Community Structure of the Denitrifying Bacteria with Nitrous Oxide Reductase Gene (nosZ I): a Long-Term Pond Experiment

Excessive nitrogen (N) input is an important factor influencing aquatic ecosystems and has received increasing public attention in the past decades. It remains unclear how N input affects the denitrifying bacterial communities that play a key role in regulating N cycles in various ecosystems. To test our hypothesis-that the abundance and biodiversity of denitrifying bacterial communities decrease with increasing N-we compared the abundance and composition of denitrifying bacteria having nitrous oxide reductase gene (nosZ I) from sediments (0-20 cm) in five experimental ponds with different nitrogen fertilization treatment (TN10, TN20, TN30, TN40, TN50) using quantitative PCR and pyrosequencing techniques. We found that (1) N addition significantly decreased nosZ I gene abundance, (2) the Invsimpson and Shannon indices (reflecting biodiversity) first increased significantly along with the increasing N loading in TN10-TN40 followed by a decrease in TN50, (3) the beta diversity of the nosZ I denitrifier was clustered into three groups along the TN concentration levels: Cluster I (TN50), Cluster II (TN40), and Cluster III (TN10-TN30), (4) the proportions of Alphaproteobacteria and Betaproteobacteria in the high-N treatment (TN50) were significantly lower than in the lower N treatments (TN10-TN30). (5) The TN concentration was the most important factor driving the alteration of denitrifying bacteria assemblages. Our findings shed new light on the response of denitrification-related bacteria to long-term N loading at pond scale and on the response of denitrifying microorganisms to N pollution.

Microbiogeochemical Traits to Identify Nitrogen Hotspots in Permafrost Regions

Permafrost-affected tundra soils are large carbon (C) and nitrogen (N) reservoirs. However, N is largely bound in soil organic matter (SOM), and ecosystems generally have low N availability. Therefore, microbial induced N-cycling processes and N losses were considered negligible. Recent studies show that microbial N processing rates, inorganic N availability, and lateral N losses from thawing permafrost increase when vegetation cover is disturbed, resulting in reduced N uptake or increased N input from thawing permafrost. In this review, we describe currently known N hotspots, particularly bare patches in permafrost peatland or permafrost soils affected by thermokarst, and their microbiogeochemical characteristics, and present evidence for previously unrecorded N hotspots in the tundra. We summarize the current understanding of microbial N cycling processes that promote the release of the potent greenhouse gas (GHG) nitrous oxide (N2O) and the translocation of inorganic N from terrestrial into aquatic ecosystems. We suggest that certain soil characteristics and microbial traits can be used as indicators of N availability and N losses. Identifying N hotspots in permafrost soils is key to assessing the potential for N release from permafrost-affected soils under global warming, as well as the impact of increased N availability on emissions of carbon-containing GHGs.

Effect of microbial community structures and metabolite profile on greenhouse gas emissions in rice varieties

Rice paddy fields are major sources of atmospheric methane (CH₄) and nitrous oxide (N₂O). Rice variety is an important factor affecting CH₄ and N₂O emissions. However, the interactive effects of rice metabolites and microorganisms on CH₄ and N₂O emissions in paddy fields are not clearly understood. In this study, a high greenhouse gas-emitting cultivar (YL 6) and a low greenhouse gas-emitting cultivar (YY 1540) were used as experimental materials. Metabolomics was used to examine the roots, root exudates, and bulk soil metabolites. High-throughput sequencing was used to determine the microbial community composition. YY 1540 had more secondary metabolites (flavonoids and isoflavonoids) in root exudates than YL 6. It was enriched with the uncultured members of the families Gemmatimonadanceae and Rhizobiales_Incertae_Sedis in bulk soil, and genera Burkholderia-Caballeronia-Paraburkholderia, Magnetospirillum, Aeromonas, and Anaeromyxobacter in roots, contributing to increased expression of pmoA and nosZ genes and reducing CH₄ and N₂O emissions. YL 6 roots and root exudates contained higher contents of carbohydrates [e.g., 6-O- acetylarbutin and 2-(3- hydroxyphenyl) ethanol 1'-glucoside] than those of YY 1540. They were enriched with genera RBG-16-58-14 in bulk soil and Exiguobacterium, and uncultured member of the Kineosporiaceae family in roots, which contributed to increased expression of mcrA, ammonia-oxidizing archaea, ammonia-oxidizing bacteria, nirS, and nirK genes and greenhouse gas emissions. In general, these results established a link between metabolites, microorganisms, microbial functional genes, and greenhouse gas emissions. The metabolites of root exudates and roots regulated CH₄ and N₂O emissions by influencing the microbial community composition in bulk soil and roots.

Anaerobic degradation of perfluorooctanoic acid (PFOA) in biosolids by Acidimicrobium sp. strain A6

Anaerobic incubations were performed with biosolids obtained from an industrial wastewater treatment plant (WWTP) that contained perfluorooctanoic acid (PFOA), and with per- and polyfluoroalkyl substances- (PFAS) free, laboratory-generated, biosolids that were spiked with PFOA. Biosolid slurries were incubated for 150 days as is, after augmenting with either Acidimicrobium sp. Strain A6 or ferrihydrite, or with both, Acidimicrobium sp. Strain A6 and ferrihydrite. Autoclaved controls were run in parallel. Only the biosolids augmented with both, Acidimicrobium sp. Strain A6 and ferrihydrite showed a decrease in the PFOA concentration, in excess of 50% (total, dissolved, and solid associated). Higher concentrations of PFOA in the biosolids spiked with PFOA and no previous PFAS exposure allowed to track the production of fluoride to verify PFOA defluorination. The buildup of fluoride over the incubation time was observed in these biosolid incubations spiked with PFOA. A significant increase in the concentration of perfluoroheptanoic acid (PFHpA) over the incubations of the filter cake samples from the industrial WWTP was observed, indicating the presence of a non-identified precursor in these biosolids. Results show that anaerobic incubation of PFAS contaminated biosolids, after augmentation with Fe(III) and Acidimicrobium sp. Strain A6 can result in PFAS defluorination.