Highly efficient ammonium removal through nitrogen assimilation by a hydrogen-oxidizing bacterium, Ideonella sp. TH17.

Ideonella sp. TH17, an autotrophic hydrogen-oxidizing bacterium (HOB), was successfully enriched and isolated from activated sludge in a domestic wastewater treatment plant (WWTP). Batch experiments were conducted to identify the cell growth and ammonium (NH4+-N) removal, and to verify the pathways of nitrogen utilization under different conditions. At a representative NH4+-N concentration of 100 mg/L in domestic wastewater, it was the first time that a HOB strain achieved a nearly 100% ammonium removal. More than 90% of NH4+-N was assimilated to biomass nitrogen by strain TH17. Only a little of N2 (<10% of initial NH4+-N) was detected without N2O emission in aerobic denitrification process. Autotrophic NH4+-N assimilation contributed predominantly to biomass nitrogen production, supplemented by assimilatory nitrate (NO3--N) reduction under aerobic conditions. A total of 17 amino acids, accounting for 54.25 ± 1.98% of the dry biomass, were detected in the bacterial biomass harvested at 72 h. These results demonstrated that the newly isolated strain TH17 was capable of removing NH4+-N and recovering nutrients from wastewater efficiently. A new solution was thus provided by this HOB strain for ammonium treatment in sustainable WWTPs of future.

Feeding and metabolism effects of three common microplastics on Tenebrio molitor L.

Mealworms from three different regions: Guangzhou, Tai'an and Shenzhen, were fed with three commonly used microplastics of polystyrene (PS), polyvinyl chloride (PVC) and low-density polyethylene (LDPE) for 1 month under favorable conditions, respectively. The survival rate and average weight of mealworms, the mass loss of microplastics and the production of frass were recorded every 4 days. Samples collected were characterized by X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analyzer and gel permeation chromatography. The results showed that mealworms from Tai'an and Shenzhen could effectively metabolize the whole microplastics tested, while those from Guangzhou could only metabolize PS and LDPE. Besides, LDPE could be degraded by mealworms from Tai'an and Shenzhen, while those from Guangzhou showed no such capability, indicating that mealworms from different regions present different metabolism effects. Furthermore, PS and LDPE are more likely to be metabolized compared with PVC.

Toxicity assessment of copper by electrochemically active bacteria in wastewater.

A bioelectrochemical sensor (BES) was constructed for toxicity assessment of copper in contaminated domestic sewage. Electrochemically active bacteria (EAB), whose growth was supported by the bioenergy generated from an in situ metallurgical process, functioned as the sensing elements. The external resistance of metallurgical BES was optimized based on linear sweep voltammetry analysis. The stabilized BES was utilized to monitor the copper toxicity in real wastewater. During the less than 1-h sensing period, copper concentration ranging from 1 to 5 mg L-1 could be detected. A power output of around 100 Wh (kg Cu)-1 and metallic copper resource were obtained simultaneously. This study demonstrated that the highly active EAB species enriched in metallurgical BES could be a promising candidate for rapid and reliable evaluation of copper toxicity in real domestic wastewater.

Magnetic chitosan/sodium alginate gel bead as a novel composite adsorbent for Cu(II) removal from aqueous solution.

Using sodium alginate hydrogel as skeleton, in combination with chitosan and magnetic Fe3O4, a new type of magnetic chitosan/sodium alginate gel bead (MCSB) was prepared. Adsorptive removal of Cu(II) from aqueous solutions was studied by using the MCSB as a promising candidate in environmental application. Different kinetics and isotherm models were employed to investigate the adsorption process. Based on Fourier transform infrared spectroscopy, field-emission scanning electron microscope, CHNS/O elements analysis, vibration magnetometer, and various means of characterization, a comprehensive analysis of the adsorption mechanism was conducted. The MCSB had a good magnetic performance with a saturation magnetization of 12.5 emu/g. Elemental analysis proved that the addition of chitosan introduced a considerable amount of nitrogen-rich groups, contributing significantly to copper adsorption onto gel beads. The contact time necessary for adsorption was optimized at 120 min to achieve equilibrium. Experimental data showed that the adsorption process agreed well with the Langmuir isotherm model and the pseudo-second-order kinetics model. The theoretical maximum adsorption capacity of MCSB for Cu(II) could reach as high as 124.53 mg/g. In conclusion, the MCSB in this study is a novel and promising composite adsorbent, which can be applied for practical applications in due course.

Uranium sequestration in sediment at an iron-rich contaminated site at Oak Ridge, Tennessee via. bioreduction followed by reoxidation.

This study evaluated uranium sequestration performance in iron-rich (30 g/kg) sediment via bioreduction followed by reoxidation. Field tests (1383 days) at Oak Ridge, Tennessee demonstrated that uranium contents in sediments increased after bioreduced sediments were re-exposed to nitrate and oxygen in contaminated groundwater. Bioreduction of contaminated sediments (1200 mg/kg U) with ethanol in microcosm reduced aqueous U from 0.37 to 0.023 mg/L. Aliquots of the bioreduced sediment were reoxidized with O2, H2O2, and NaNO3, respectively, over 285 days, resulting in aqueous U of 0.024, 1.58 and 14.4 mg/L at pH 6.30, 6.63 and 7.62, respectively. The source- and the three reoxidized sediments showed different desorption and adsorption behaviors of U, but all fit a Freundlich model. The adsorption capacities increased sharply at pH 4.5 to 5.5, plateaued at pH 5.5 to 7.0, then decreased sharply as pH increased from 7.0 to 8.0. The O2-reoxidized sediment retained a lower desorption efficiency at pH over 6.0. The NO3--reoxidized sediment exhibited higher adsorption capacity at pH 5.5 to 6.0. The pH-dependent adsorption onto Fe(III) oxides and formation of U coated particles and precipitates resulted in U sequestration, and bioreduction followed by reoxidation can enhance the U sequestration in sediment.

Bacterial Community Shift and Coexisting/Coexcluding Patterns Revealed by Network Analysis in a Uranium-Contaminated Site after Bioreduction Followed by Reoxidation.

A site in Oak Ridge, TN, USA, has sediments that contain >3% iron oxides and is contaminated with uranium (U). The U(VI) was bioreduced to U(IV) and immobilized in situ through intermittent injections of ethanol. It then was allowed to reoxidize via the invasion of low-pH (3.6 to 4.0), high-nitrate (up to 200 mM) groundwater back into the reduced zone for 1,383 days. To examine the biogeochemical response, high-throughput sequencing and network analysis were applied to characterize bacterial population shifts, as well as cooccurrence and coexclusion patterns among microbial communities. A paired t test indicated no significant changes of α-diversity for the bioactive wells. However, both nonmetric multidimensional scaling and analysis of similarity confirmed a significant distinction in the overall composition of the bacterial communities between the bioreduced and the reoxidized sediments. The top 20 major genera accounted for >70% of the cumulative contribution to the dissimilarity in the bacterial communities before and after the groundwater invasion. Castellaniella had the largest dissimilarity contribution (17.7%). For the bioactive wells, the abundance of the U(VI)-reducing genera Geothrix, Desulfovibrio, Ferribacterium, and Geobacter decreased significantly, whereas the denitrifying Acidovorax abundance increased significantly after groundwater invasion. Additionally, seven genera, i.e., Castellaniella, Ignavibacterium, Simplicispira, Rhizomicrobium, Acidobacteria Gp1, Acidobacteria Gp14, and Acidobacteria Gp23, were significant indicators of bioactive wells in the reoxidation stage. Canonical correspondence analysis indicated that nitrate, manganese, and pH affected mostly the U(VI)-reducing genera and indicator genera. Cooccurrence patterns among microbial taxa suggested the presence of taxa sharing similar ecological niches or mutualism/commensalism/synergism interactions.IMPORTANCE High-throughput sequencing technology in combination with a network analysis approach were used to investigate the stabilization of uranium and the corresponding dynamics of bacterial communities under field conditions with regard to the heterogeneity and complexity of the subsurface over the long term. The study also examined diversity and microbial community composition shift, the common genera, and indicator genera before and after long-term contaminated-groundwater invasion and the relationship between the target functional community structure and environmental factors. Additionally, deciphering cooccurrence and coexclusion patterns among microbial taxa and environmental parameters could help predict potential biotic interactions (cooperation/competition), shared physiologies, or habitat affinities, thus, improving our understanding of ecological niches occupied by certain specific species. These findings offer new insights into compositions of and associations among bacterial communities and serve as a foundation for future bioreduction implementation and monitoring efforts applied to uranium-contaminated sites.

Metabolomics Uncovers the Regulatory Pathway of Acyl-homoserine Lactones Based Quorum Sensing in Anammox Consortia.

Acyl-homoserine lactones (AHLs)-mediated quorum sensing in bacterial communities have been extensively observed. However, the metabolic pathways regulated by AHLs in bacteria remain elusive. Here, we combined long-term reactor operation with microbiological and metabolomics analyses to explore the regulatory pathways for different AHLs in anammox consortia, which perform promising nitrogen removal for wastewater treatment. The results showed that no obvious shifts induced by exogenous AHLs occurred in the microbial community and, mainly, dosing AHLs induced changes in the metabolites. 3OC6-HSL, C6-HSL, and C8-HSL controlled the electron transport carriers that influence the bacterial activity. In contrast, only 3OC6-HSL regulated LysoPC(20:0) metabolism, which affected bacterial growth. AHLs mainly regulated the synthesis of the amino acids Ala, Val, and Glu and selectively regulated Asp and Leu to affect extracellular proteins. Simultaneously, all the AHLs regulated the ManNAc biosynthetic pathways, while OC6-HSL, OC8-HSL, and C6-HSL particularly enriched the UDP-GlcNAc pathway to promote exopolysaccharides, resulting in different aggregation levels of the anammox consortia. Our results not only provide the first metabolic insights into the means by which AHLs affect anammox consortia but also hint at potential strategies for overcoming the limitations of the long start-up period required for wastewater treatment by anammox processing.

Genome-Centered Metagenomics Analysis Reveals the Symbiotic Organisms Possessing Ability to Cross-Feed with Anammox Bacteria in Anammox Consortia.

Although using anammox communities for efficient wastewater treatment has attracted much attention, the pure anammox bacteria are difficult to obtain, and the potential roles of symbiotic bacteria in anammox performance are still elusive. Here, we combined long-term reactor operation, genome-centered metagenomics, community functional structure, and metabolic pathway reconstruction to reveal multiple potential cross-feedings during anammox reactor start-up according to the 37 recovered metagenome-assembled genomes (MAGs). We found Armatimonadetes and Proteobacteria could contribute the secondary metabolites molybdopterin cofactor and folate for anammox bacteria to benefit their activity and growth. Chloroflexi-affiliated bacteria encoded the function of biosynthesizing exopolysaccharides for anammox consortium aggregation, based on the partial nucleotide sugars produced by anammox bacteria. Chlorobi-affiliated bacteria had the ability to degrade extracellular proteins produced by anammox bacteria to amino acids to affect consortium aggregation. Additionally, the Chloroflexi-affiliated bacteria harbored genes for a nitrite loop and could have a dual role in anammox performance during reactor start-up. Cross-feeding in anammox community adds a different dimension for understanding microbial interactions and emphasizes the importance of symbiotic bacteria in the anammox process for wastewater treatment.

Cell surface engineering of microorganisms towards adsorption of heavy metals.

Heavy metal contamination has become a worldwide environmental concern due to its toxicity, non-degradability and food-chain bioaccumulation. Conventional physical and chemical treatment methods for heavy metal removal have disadvantages such as cost-intensiveness, incomplete removal, secondary pollution and the lack of metal specificity. Microbial biomass-based biosorption is one of the approaches gaining increasing attention because it is effective, cheap, and environmental friendly and can work well at low concentrations. To enhance the adsorption properties of microbial cells to heavy metal ions, the cell surface display of various metal-binding proteins/peptides have been performed using a cell surface engineering approach. The surface engineering of Gram-negative bacteria, Gram-positive bacteria and yeast towards the adsorption of heavy metals are reviewed in this article. The problems and future perspectives of this technology are discussed.

Construction and optimization of a Pseudomonas putida whole-cell bioreporter for detection of bioavailable copper.

A Pseudomonas putida whole-cell bioreporter for detecting bioavailable copper was constructed by inserting a CueR-regulated sensor element upstream of a promoterless green fluorescent protein (GFP) reporter gene. The constructed bioreporter cells expressed GFP only in response to Cu and Ag when cultivated in different metal salt solutions. M9 supplemented medium provided higher sensitivity compared with LB medium. The optimal test condition was cell suspension with an OD600 of 0.4-0.5 incubated at 30 °C. The detection range of Cu is 1-70 mg/l under optimal test condition in M9 supplemented medium.

An integrated meta-omics approach reveals the different response mechanisms of two anammox bacteria towards fluoroquinolone antibiotics.

The emerging fluoroquinolone antibiotics (FQs) are highly influential in nitrogen removal from livestock wastewater. However, beyond the capability of nitrogen removal, little is known about the molecular mechanisms (e.g., shift of core metabolism and energy allocation) of different anaerobic ammonium-oxidizing bacteria (AnAOB) under continuous FQ stress. This study investigated the effects of ciprofloxacin, ofloxacin and their mixture at concentrations detected in livestock wastewater on two key anammox species in membrane bioreactors. It was found 20 µg/L FQs promoted nitrogen removal efficiency and community stability, and42-51 % of FQs were removed simultaneously. Integrated meta-omics analysis revealed varied gene expression patterns between the two dominant AnAOB, Candidatus Brocadia sapporoensis (B AnAOB) and Candidatus Kuenenia stuttgartiensis (K AnAOB). The nitrogen metabolic processes were bolstered in B AnAOB, while those involved in anammox pathway of K AnAOB were inhibited. This difference was tentatively attributed to the up-regulation of reactive oxygen species scavenger genes (ccp and dxf) and FQ resistance gene (qnrB72) in B AnAOB. Importantly, most enhanced core biosynthesis/metabolism of AnAOB and close cross-feeding with accompanying bacteria were also likely to contribute to their higher levels of biomass yield and metabolism activity under FQ stress. This finding suggests that B AnAOB has the advantage of higher nitrogen metabolism capacity over K AnAOB in livestock wastewater containing FQs, which is helpful for efficient and stable nitrogen removal by the functional anammox species.

Optimizing cadmium and mercury specificity of CadR-based E. coli biosensors by redesign of CadR.

The metalloprotein, CadR, was redesigned to optimize cadmium and mercury specificity of CadR-based E. coli biosensors. By truncating 10 and 21 amino acids from the C-terminal extension of CadR, CadR-TC10 and CadR-TC21 were obtained, respectively. The genes cadR, cadR-TC10 and cadR-TC21 were used as sensing elements to construct green fluorescent protein based E.coli biosensors. Induction at 30 °C for 4 h in supplemented M9 medium was the optimized condition for the biosensor. Compared with CadR-based biosensor, there was a clear decline in induction coefficient for CadR-TC21-based biosensor (decreased by 86 % in Zn(II), 44 % in Hg(II), and only 37 % in Cd(II)). While in CadR-TC10-based biosensor, the induction coefficient decreased by 95 % in Zn(II), 70 % in Hg(II), and 67 % in Cd(II). Improved performances of CadR mutants based E. coli biosensors indicated that truncating C-terminal extension of CadR could improve the specificity.

Molecular insights into enhanced nitrogen removal induced by trace fluoroquinolone antibiotics in an anammox system.

It has been widely reported that fluoroquinolones (FQs) can affect the anaerobic ammonium oxidization (anammox) microorganisms, which interferes with the performance of nitrogen removal from wastewater. However, the metabolic mechanism of anammox microorganisms responding to FQs has rarely been explored. In this study, it was found that 20 µg/L FQs promoted the nitrogen removal performance of anammox microorganisms in batch exposure assays, and 36-51% of FQs were removed simultaneously. Combined metabolomics and genome-resolved metagenomic analysis revealed up-regulated carbon fixation in anammox bacteria (AnAOB), while purine and pyrimidine metabolism, protein generation and transmembrane transport were enhanced in AnAOB and symbiotic bacteria by 20 µg/L FQs. Consequently, hydrazine dehydrogenation, nitrite reduction, and ammonium assimilation were bolstered, improving the nitrogen removal efficiency of the anammox system. These results revealed the potential roles of specific microorganisms in response to emerging FQs and provided further information for practical application of anammox technology in wastewater treatment.

Spatiotemporal distribution, source apportionment and risk assessment of typical hormones and phenolic endocrine disrupting chemicals in environmental and biological samples from the mariculture areas in the Pearl River Delta, China.

The present work studied the levels, distribution, potential sources, ecological and human health risks of typical hormones and phenolic endocrine disrupting chemicals (EDCs) in the mariculture areas of the Pearl River Delta (PRD), China. The environmental levels of 11 hormones (6 estrogens, 4 progestogens, and 1 androgen) and 2 phenolic EDCs were quantified in various matrices including water, sediment, cultured fish and shellfish. Ultrahigh performance liquid chromatography-triple quadrupole tandem mass spectrometry analyses showed that all the 13 target compounds were detected in biotic samples, whereas 10 were detected in water and sediment, respectively. The total concentrations ranged from 35.06-364.53 ng/L in water and 6.31-29.30 ng/g in sediment, respectively. The average contaminant levels in shellfish (Ostrea gigas, Mytilus edulis and Mimachlamys nobilis) were significantly higher than those in fish (Culter alburnus, Ephippus orbis and Ephippus orbis). Source apportionment revealed that the pollution of hormones and phenolic EDCs in PRD mariculture areas was resulted from the combination of coastal anthropogenic discharges and mariculture activities. The hazard quotient values of the contaminants were all less than 1, implying no immediate human health risk. Overall, the present study is of great significance for scientific mariculture management, land-based pollution control, ecosystem protection, and safeguarding human health.

Sustainable treatment of nitrate-containing wastewater by an autotrophic hydrogen-oxidizing bacterium.

Bacteria are key denitrifiers in the reduction of nitrate (NO3 --N), which is a contaminant in wastewater treatment plants (WWTPs). They can also produce carbon dioxide (CO2) and nitrous oxide (N2O). In this study, the autotrophic hydrogen-oxidizing bacterium Rhodoblastus sp. TH20 was isolated for sustainable treatment of NO3 --N in wastewater. Efficient removal of NO3 --N and recovery of biomass nitrogen were achieved. Up to 99% of NO3 --N was removed without accumulation of nitrite and N2O, consuming CO2 of 3.25 mol for each mole of NO3 --N removed. The overall removal rate of NO3 --N reached 1.1 mg L-1 h-1 with a biomass content of approximately 0.71 g L-1 within 72 h. TH20 participated in NO3 --N assimilation and aerobic denitrification. Results from 15N-labeled-nitrate test indicated that removed NO3 --N was assimilated into organic nitrogen, showing an assimilation efficiency of 58%. Seventeen amino acids were detected, accounting for 43% of the biomass. Nitrogen loss through aerobic denitrification was only approximately 42% of total nitrogen. This study suggests that TH20 can be applied in WWTP facilities for water purification and production of valuable biomass to mitigate CO2 and N2O emissions.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics.

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

Identification of quorum sensing signal AHLs synthases in Candidatus Jettenia caeni and their roles in anammox activity.

Acyl-homoserine lactone (AHL)-based quorum sensing (QS) in the anaerobic ammonium oxidizing (anammox) consortia has attracted increasing attention. However, AHL synthase in anammox bacteria and the relationship between AHL synthetic genes and anammox activity are still not clear because anammox bacteria have not been isolated from the consortia. Two novel synthases of AHLs (JqsI-1 and JqsI-2), which are HdtS-type rather than the widely studied LuxI-type, were identified in anammox bacteria Candidatus Jettenia caeni and synthesized four AHLs. There was a correlation between AHL concentration, in situ transcriptional expression of the AHL synthase genes (jqsI-1 and jqsI-2) and genetic marker of anammox activity (hydrazine synthase gene, hzsA). And AHL add-back studies demonstrated that AHL influence the expression of hzsA to regulate anammox bacterial activity. This study provides insight into the QS communication pathway of anammox bacteria for wastewater treatment.

Pharmaceuticals and personal care products in water, sediments, aquatic organisms, and fish feeds in the Pearl River Delta: Occurrence, distribution, potential sources, and health risk assessment.

This study investigated the occurrence, distribution, and potential sources of 34 pharmaceuticals and personal care products (PPCPs) in water, sediments, aquatic organisms (fish and shellfish), and fish feeds from the mariculture areas of the Pearl River Delta (PRD). The health risk presented by this class of compounds was also assessed in relation to their intake via seafood consumption. Of the 34 PPCPs, a total of 9, 21, 14, and 28 PPCPs were detected in water, sediments, fish feeds, and aquatic organisms, respectively. Trimethoprim, norfloxacin, ofloxacin, and spectinomycin were detected in all matrices. The levels of PPCPs in water and sediment samples were relatively low. Spectinomycin, paracetamol, ciprofloxacin, norfloxacin, and ibuprofen were the most frequently detected PPCPs in feeds. Ibuprofen and ketoprofen were widely detected in aquatic organisms, with average concentrations of 562 and 267 ng/g wet weight, respectively. The residual levels of PPCPs in shellfish such as ME (mussel, Mytilus edulis) and OS (oyster, Ostrea gigas) were significantly higher (p < 0.05) than those in other species including CA (topmouth culter, Culter alburnus) and EO (orbfish, Ephippus orbis). Correlation analysis indicated that the medicated feeds were a potential source of PPCPs in the mariculture areas of the PRD, but other anthropogenic sources should not be ignored. Based on maximum residue limits and acceptable daily intake, the health risks presented to humans via seafood consumption are negligible. However, as multiple antibiotics were frequently detected in the mariculture environment, aquatic organisms, and feeds, the induction and dissemination of antimicrobial resistance associated with antibiotic usage in aquaculture would be of great concern. It is necessary to establish a centralized management system and control the use of veterinary drugs in mariculture to protect the aquaculture environment and ensure the safety of seafood.