Influence and mechanism of typical transition metal ions on the denitrification performance of heterotrophic nitrification-aerobic denitrification bacteria.

To investigate the inhibitory effects of various transition metal ions on nitrogen removal and their underlying mechanisms, the single and combined effects of Cu2+ Ni2+ and Zn2+ on Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria Acinetobacter sp. TAC-1 were studied in a batch experiment system. The results revealed that increasing concentrations of Cu2+ and Ni2+ had a detrimental effect on the removal of ammonium nitrogen (NH4+-N) and total nitrogen (TN). Specifically, Cu2+ concentration of 10 mg/L, the TN degradation rate was 55.09%, compared to 77.60% in the control group. Cu2+ exhibited a pronounced inhibitory effect. In contrast, Zn2+ showed no apparent inhibitory effect on NH4+-N removal and even enhanced TN removal at lower concentrations. However, when the mixed ion concentration of Zn2++Ni2+ exceeded 5 mg/L, the removal rates of NH4+-N and TN were significantly reduced. Moreover, transition metal ions did not significantly impact the removal rates of chemical oxygen demand (COD). The inhibition model fitting results indicated that the inhibition sequence was Cu2+ > Zn2+ > Ni2+. Transcriptome analysis demonstrated that metal ions influence TAC-1 activity by modulating the expression of pivotal genes, including zinc ABC transporter substrate binding protein (znuA), ribosomal protein (rpsM), and chromosome replication initiation protein (dnaA) and DNA replication of TAC-1 under metal ion stress, leading to disruptions in transcription, translation, and cell membrane structure. Finally, a conceptual model was proposed by us to summarize the inhibition mechanism and possible response strategies of TAC-1 bacteria under metal ion stress, and to address the lack of understanding regarding the influence mechanism of TAC-1 on nitrogen removal in wastewater co-polluted by metal and ammonia nitrogen. The results provided practical guidance for the management of transition metal and ammonia nitrogen co-polluted water bodies, as well as the removal of high nitrogen.

Research on the application of heterotrophic nitrification-aerobic denitrification bacteria in membrane bioreactor (MBR).

Inoculating heterotrophic nitrification-aerobic denitrification bacteria (HN-AD) to enhance membrane bioreactor (MBR) efficiency may result in the loss of functional bacteria. Therefore, this study compares the application results of enhancing MBR with a self-designed biological amplifier coupled with HN-AD against the performance of conventional MBR. After enhancement, the MBR achieved a removal efficiency of 96.7% for NH4+-N (100 mg/L) and 96.4% for COD (400 mg/L) in synthetic wastewater. There was a 33% increase in TN (100 mg/L) removal efficiency. The dominant bacteria in the MBR were Alcaligenes (48.4%) and Thauera (15.2%). Additionally, the abundance of denitrification genes (nirK, norB, nosZ) increased in the enhanced MBR, contributing to improved TN removal efficiency. The use of a biological amplifier effectively solved the problem of HN-AD loss in sewage treatment.

Quantitative analysis of TCE biodegradation pathway in landfill cover utilizing continuous monitoring, droplet digital PCR and multi-omics sequencing technology.

The remediation of volatile chlorinated hydrocarbons in the quasi-vadose zone has become a significant challenge. We applied an integrated approach to assess the biodegradability of trichloroethylene to identify the biotransformation mechanism. The formation of the functional zone biochemical layer was assessed by analyzing the distribution of landfill gas, physical and chemical properties of cover soil, spatial-temporal variations of micro-ecology, biodegradability of landfill cover soil and distributional difference metabolic pathway. Real-time online monitoring showed that trichloroethylene continuously undergoes anaerobic dichlorination and simultaneous aerobic/anaerobic conversion-aerobic co-metabolic degradation on the vertical gradient of the landfill cover system and reduction in trans-1,2-dichloroethylene in the anoxic zone but not 1,1-dichloroethylene. PCR and diversity sequencing revealed the abundance and spatial distribution of known dichlorination-related genes within the landfill cover, with 6.61 ± 0.25 × 104-6.78 ± 0.09 × 106 and 1.17 ± 0.78 × 103-7.82 ± 0.07 × 105 copies per g/soil of pmoA and tceA, respectively. In addition, dominant bacteria and diversity were significantly linked with physicochemical factors, and Mesorhizobium, Pseudoxanthomonas and Gemmatimonas were responsible for biodegradation in the aerobic, anoxic and anaerobic zones. Metagenome sequencing identified 6 degradation pathways of trichloroethylene that may occur in the landfill cover; the main pathway was incomplete dechlorination accompanied by cometabolic degradation. These results indicate that the anoxic zone is important for trichloroethylene degradation.

Microecological health assessment of water environment and sediment based on metagenomics: a case study of Guixi River in Chongqing, China.

River sediment is vital in containing water pollution and strengthening water remediation. This paper has conducted a study on the microecological health assessment of the sediment and water body of Guixi River in Dianjiang, Chongqing, China, using metagenomics sequencing and microbial biological integrity index (M-IBI) technology. The analysis of physical and chemical characteristics shows that the concentration of TN varies from 2.62 to 9.76 mg/L in each sampling section, and the eutrophication of the water body is relatively severe. The proportion of Cyanobacteria in the sampling section at the sink entrance is higher than that of other sites, where there are outbreaks of water blooms and potential hazards to human health. The dominant functions of each site include carbon metabolism, TCA cycle, and pyruvate metabolism. In addition, the main virulence factors and antibiotic resistance genes in sediment are Type IV pili (VF0082), LOS (CVF494), MymA operon (CVF649), and macrolide resistance genes macB, tetracyclic tetA (58), and novA. Correlation analysis of environmental factors and microorganisms was also performed, and it was discovered that Thiothrix and Acidovorax had obvious gene expression in the nitrogen metabolism pathway, and the Guixi River Basin had a self-purification capacity. Finally, based on the microecological composition of sediment and physical and chemical characteristics of the water body, the health assessment was carried out, indicating that the main pollution area was Dianjiang Middle School and the watershed near the sewage treatment plant. The findings should theoretically support an in-depth assessment of the water environment's microecological health.

Effect mechanism of individual and combined salinity on the nitrogen removal yield of heterotrophic nitrification-aerobic denitrification bacteria.

One of the biggest challenges of applying heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria to treat high salt organic wastewater lies in the inhibitory effect exerted by salinity. To study the inhibition effect and underlying mechanism induced by different ion types and ion composition, the individual and combined effects of NaCl, KCl and Na2SO4 on HN-AD bacteria Acinetobacter sp. TAC-1 were systematically investigated by batch experiments. Results indicated that the ammonia nitrogen removal yield and TAC-1 activity decreased with increased salt concentration. NaCl, KCl and Na2SO4 exerted different degrees of inhibition on TAC-1, with half concentration inhibition constant values of 0.205, 0.238 and 0.110 M, respectively. A synergistic effect on TAC-1 was found with the combinations of NaCl + KCl, NaCl + Na2SO4 and NaCl + KCl + Na2SO4. The whole RNA resequencing suggested that transcripts of denitrification genes (nirB and nasA) were significantly downregulated with increased Na2SO4 concentration. Simultaneously, Na2SO4 stress disrupted cell respiration, DNA replication, transcription, translation, and induced oxidative stress. Finally, we proposed a conceptual model to summarize the inhibition mechanisms and possible response strategies of TAC-1 bacteria under Na2SO4 stress.

Cometabolic degradation mechanism and microbial network response of methanotrophic consortia to chlorinated hydrocarbon solvents.

The cometabolism mechanism of chlorinated hydrocarbon solvents (CHSs) in mixed consortia remains largely unknown. CHS biodegradation characteristics and microbial networks in methanotrophic consortia were studied for the first time. The results showed that all CHSs can efficiently be degraded via cometabolism with a maximum degradation rate of 4.8 mg/(h·gcell). Chloroalkane and chloroethylene were more easily degraded than chlorobenzenes by methanotrophic consortia, especially nonfully chlorinated aliphatic hydrocarbons, which were converted to Cl- with a production rate of 0.29-0.36 mg/(h·gcell). In addition, the microecological response results indicated that Methylocystaceae (49.0%), Methylomonas (65.3%) and Methylosarcina (41.9%) may be the major functional degraders in methanotrophic consortia. Furthermore, the results of the microbial correlation network suggested that interactive relationships constructed by type I methanotrophs and heterotrophs determined biodegradability. Additionally, PICRUSt analysis showed that CHSs could increase the relative abundance of CHS degradation genes and reduce the relative abundance of methane oxidation genes, which was in good agreement with the experimental results.

Efficiency and microbial diversity of aeration solid-phase denitrification process bioaugmented with HN-AD bacteria for the treatment of low C/N wastewater.

To evaluate the simultaneous nitrification and denitrification (SND) performance of the aeration solid-phase denitrification (SPD) process and improve the operating efficiency, aeration SPD process using polybutanediol succinate as carbon source was optimized and the process was bioaugmented with heterotrophic nitrification-aerobic denitrification bacteria for the treatment of real wastewater. The results showed that after bioaugmentation, the total nitrogen removal efficiency of the aeration SPD process increased by 50.46 % under condition of dissolved oxygen (DO) 3 mg/L. According to Illumina MiSeq sequencing and correlation analyses, the microbial community can perform SND under the conditions of DO 5 mg and HRT 6 h, but is susceptible to DO. Bioaugmentation mainly affected the carbon source metabolic network with heterotrophic bacteria Methyloversatilis, Thiothrix, and norank_Lentimicrobiaceae as nodes to change the community structure, thereby improving the performance of the functional microbial community. Kyoto Encyclopedia of Genes and Genomes analysis suggested that narB, narG, narH, nirK and narI were the key genes involved in the response to bioaugmentation. This work provides new insights for the application of the SPD process in wastewater treatment.

Biodegradation of phenol by a highly tolerant strain Rhodococcus ruber C1: Biochemical characterization and comparative genome analysis.

A novel phenol-degrading strain was isolated and identified as Rhodococcus ruber C1. The degradation analysis shows that 1806 mg/L of phenol can be completely degraded by strain C1 within 38 h, and the maximum specific growth rate (µmax=1.527 h-1) and maximum specific phenol degradation rate (qmax=3.674 h-1) indicate its excellent phenol metabolism capability. More importantly, phenol can be degraded by strain C1 in the temperature range of 20-45 °C within 72 h, and with longer degradation time, phenol can be completely degraded even at 10, 15 and 50 °C. The whole genome of strain C1 was sequenced, and a comparative genome analysis of strain C1 with 36 other genomes of Rhodococcus was performed. A remarkable gene family expansion occurred during the evolution of Rhodococcus, and a comprehensive evolutionary picture of Rhodococcus at genomic level was presented. Moreover, the copy number of genes involved in phenol metabolism was compared among genus Rhodococcus, and the results demonstrate high phenol degradation capability of strain C1 at genomic level. These findings suggest that Rhodococcus ruber C1 is a bacterium capable of degrading phenol efficiently in the temperature range of 10-50 °C.

Efficient production of polymalic acid from xylose mother liquor, an environmental waste from the xylitol industry, by a T-DNA-based mutant of Aureobasidium pullulans.

Polymalic acid (PMA) is a biodegradable polymer produced by the polyextremotolerant fungi Aureobasidium pullulans and has been shown to have potential applications in environmental fields. In this work, a high PMA yield mutant FJ-D2 was screened from T-DNA-based mutant libraries and showed a 12.9% increase in PMA titers, which was attributed to decreased the expression of a glycosyltransferase gene (celA), resulting in a 39.5% reduction in cellulose biosynthesis. Untreated waste xylose mother liquor (WXML), an environmental waste generated from the xylitol industry, can be directly used as an economical substrate for PMA production. Using batch-fermentation of FJ-D2, the PMA titer of 57.1 ± 0.02 g/L was produced in a 5-L fermentor, with the highest MA yield of 0.77 g/g mixed sugar. Furthermore, compared with ethylenediaminetetraacetic acid (EDTA), PMA had a comparable cadmium (Cd) removal efficiency (88.7% for EDTA versus 86.0% for PMA), which was not found in the monomer of L-malic acid (MA) monomers. These findings indicated that PMA was an environmentally friendly and biodegradable chelator for soil remediation. Moreover, our results provided an economically competitive process for PMA production from renewable environmental wastes.

Temporal and spatial variation in the mechanisms used by microorganisms to form methylmercury in the water column of Changshou Lake.

The microbiome in artificial lake water and its impact on mercury (Hg) methylation remain largely unknown. We selected the largest artificial lake in southeastern china, Changshou Lake (CSL), which has high background levels of Hg, for our investigation of Hg transformation microorganisms. Five different sections of the water column of CSL were sampled during four seasons. The water samples were subjected to analysis of geochemical parameters, various Hg species and microbiome information. High concentrations of total mercury (THg) were detected in CSL in comparison with those found in natural lakes. Significant differences in microbial community structure and Hg species abundance existed among seasons. High dissolved methyl mercury (DMeHg) formation and high bacterial richness and diversity occurred in the fall. The microbiome was dominated by Proteobacteria, Actinobacteria, Bacteroidetes, Deinococcus-Thermus and many unclassified bacteria. Significant correlations were found between seasonal bacterial communities and Hg levels. Hg methylation was strongly linked to the abundance of Cyanobacteria. Methylators, including Syntrophus, Desulfovibrio and Desulfomonile species, were detected only in samples collected in the fall. The results of enzyme functional analyses revealed that many unknown types of bacteria could also be responsible for Hg transformation. This study was the first to investigate the impact of various Hg species on the microbiome of artificial lake water. The findings of this study illuminate the role of seasonal bacteria in Hg transformation.

Genetic response analysis of Beauveria bassiana Z1 under high concentration Cd(II) stress.

Cadmium (Cd(II)) has carcinogenic and teratogenic toxicity, which can be accumulated in the human body through the food chain, endangering human health and life. In this study, a highly Cd(II)-tolerant fungus named Beauveria bassiana Z1 was studied, and its Cd(Ⅱ) removal efficiency was 71.2% when the Cd(II) concentration was 10 mM. Through bioanalysis and experimental verification of the transcriptome data, it was found that cadmium entered the cells through calcium ion channels, and then complexed with intracellular glutathione (GSH) and stored in vacuoles or excluded extracellular by ABC transporters. Cytochrome P450 was significantly upregulated in many pathways and actively participated in detoxification related reactions. The addition of cytochrome inhibitor taxifolin reduced the removal efficiency of Cd(II) by 45%. In the analysis, it demonstrated that ACOX1 gene and OPR gene of jasmonic acid (JA) synthesis pathway were significantly up-regulated, and were correlated with bZIP family transcription factors cpc-1_0 and pa p1_0. The results showed that exogenous JA could improve the removal efficiency of Cd(II) by strain Z1.

Efficient and low-energy degradation of chlorobenzene via catA-mediated cleavage and bedC1 docking in a novel Burkholderia stabilis TF-2.

In this study, a novel strain Burkholderia stabilis TF-2 capable of assimilatory and co-metabolic degradation of chlorobenzenes was obtained. The interaction between chlorobenzene (CB) and target enzymes, as well as the metabolic pathways in TF-2, were elucidated using multi-omics and molecular docking techniques. Results of degradation experiments indicated that TF-2 assimilated CB at a rate of 0.22-0.66 mg·gcell-1·h-1 in concentrations of 20-200 mg L-1. Additionally, TF-2 also used sodium succinate and sodium citrate as substrates to co-metabolize CB, with degradation rates of 0.26-2.00 and 0.31-1.72 mol·gcell-1·h-1, respectively. Whole-genome sequencing revealed over 18 novel genes associated with aromatic hydrocarbon degradation in TF-2. Transcriptomic analysis showed that CB induced the high expression of 119 genes involved in CB metabolism and late mineralization. The significant up-regulation of the bedC1 (encoding a ring-hydroxylated dioxygenase), CatA (chlorocatechol 1,2-dioxygenase), pcaJ (3-oxoadipate CoA-transferase alpha subunit) and fadA (acetyl-CoA acyltransferase) genes facilitated CB metabolism. Based on these findings, a metabolic pathway for CB was constructed, with the key step involving ortho cleavage of the aromatic ring under the action of the catA gene. Furthermore, molecular docking revealed that CB bound to bedC1 with -4.5 kcal mol-1 through hydrophobic bonds, π-stacking, and a halogen bond. These results provide strong support for development of efficient strains to enhance the removal of chlorinated organic compounds.

Characterization of Methylocystis strain JTA1 isolated from aged refuse and its tolerance to chloroform.

To accelerate the efficiency of methane biodegradation in landfills, a Gram-negative, rod-shaped, non-motile, non-spore-forming bacterium, JTA1, which can utilize methane as well as acetate, was isolated from the Laogang MSW landfills, Shanghai, China. Strain JTA1 was a member of genus Methylocystis on the basis of 16S rRNA and pmoA gene sequence similarity. The maximum specific cell growth rates (micro(max) = 0.042 hr(-1), R2 = 0.995) was derived through Boltzmann simulation, and the apparent half-saturation constants (K(m(app)) = 7.08 mmol/L, R2 = 0.982) was calculated according to Michaelis-Menton hyperbolic model, indicating that Methylocystis strain JTA1 had higher-affinity potential for methane oxidation than other reported methanotrophs. By way of adding the strain JTA1 culture, the methane consumption of aged refuse reached 115 mL, almost two times of control experiment. In addition, high tolerance of Methylocystis strain JTA1 to chloroform could facilitate the methane oxidation of aged refuse bio-covers. At the chloroform concentration of 50 mg/L, the methane-oxidation rate of bio-cover reached 0.114 mL/(day x g), much higher than the highest rate, 0.0135 mL/(day x g), of reported bio-covers. In conclusion, strain JTA1 opens up a new possibility for environmental biotechnology, such as soil or landfills bioremediation and wastewater decontamination.

[Research progress and discovery process of facultative methanotrophs--a review].

Facultative methanotrophs are a group of phylogenetically diverse microorganisms characterized by their ability to use methane and some other compounds containing C-C bond as their sole source of carbon and energy. Recently, which belong to the facultative methanotrophs in the genera Methylocella, Methylocapsa and Methylocystis, which belong to the Alphaproteobacteria, have been reported that can grow on larger organic acids or ethanol for some species, as well as methane. In this paper, the research history of facultative methanotrophs was summarized systematically, some other facultative methane-oxidizing microorganisms were introduced, the metabolic mechanisms of utilizing multi-carbon compounds by facultative methanotrophs were analyzed, and the current problems and the future engineering applications were discussed.

Domestication and pilot-scale culture of mixed bacteria HY-1 capable of heterotrophic nitrification-aerobic denitrification.

To further investigate the potential of heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria for practical applications, the HN-AD mixed bacteria HY-1 were enriched and domesticated in this study. After five generations of domestication, the mixture was able to remove 98% of ammonia nitrogen (400 mg/L) and 81.9% of mixed nitrogen source (nitrate, nitrite). Changes in community structure in the domestication process of mixed microorganisms were studied using 16S rDNA-seq. The results indicated an increase in the abundance of Acinetobacter from 16.9% to 80%. The conditions for the expanded culture of the HY-1 were also optimized. Moreover, A pilot-scale expanded reactor with a capacity of 1000L was constructed, and the HY-1 was successfully expanded from 0.1L to 800L. The community structures of the HY-1 remained stable after the expanded culture, with Acinetobacter as the dominant species. Moreover, the HY-1 demonstrated adaptability to actual high ammonia nitrogen wastewater and showed potential for practical application.

Metabolic diversity shapes vegetation-enhanced methane oxidation in landfill covers: Multi-omics study of rhizosphere microorganisms.

Vegetation root exudates have the ability to shape soil microbial community structures, thereby enhancing CH4 bio-oxidation capacity in landfill cover systems. In this study, the CH4 oxidation capacity of indigenous vegetation rhizosphere microorganisms within operational landfill covers in Chongqing, China, was investigated for the first time, with the objective of identifying suitable plant candidates for CH4 mitigation initiatives within landfill cover systems. Furthermore, a multi-omics methodology was employed to explore microbial community structures and metabolic variances within the rhizospheric environment of diverse vegetation types. The primary aim was to elucidate the fundamental factors contributing to divergent CH4 oxidation capacities observed in rhizosphere soils. The findings demonstrated that herbaceous vegetation predominated in landfill covers. Notably, Rumex acetosa exhibited the highest CH4 oxidation capacity in the rhizosphere soil, approximately 20 times greater than that in non-rhizosphere soil. Root exudates played a crucial role in inducing the colonization of CH4-oxidizing functional microorganisms in the rhizosphere, subsequently prompting the development of specific metabolic pathways. This process, in turn, enhanced the functional activity of the microorganisms while concurrently bolstering their tolerance to microbial pollutants. Consequently, the addition of substances like Limonexic acid strengthened the CH4 bio-oxidation process, thereby underscoring the suitability of Rumex acetosa and similar vegetation species as preferred choices for landfill cover vegetation restoration.

Water microecology is affected by seasons but not sediments: A spatiotemporal dynamics survey of bacterial community composition in Lake Changshou-The largest artificial lake in southwest China.

This study aimed to evaluate the correlation between microecology of sediments and water as well as their spatial-temporal variations in Changshou Lake. The results demonstrated that microecology in the lake exhibits spatiotemporal heterogeneity, and microbial diversity of sediments was significantly higher than that of water body. Further, it was found that there was statistically insignificant positive correlation between microecology of sediments and that of water body. PCoA and community structure analysis revealed that the predominant phyla which exhibited significant spatial differences in sediments were Proteobacteria, Actinobacteria and Planctomycetes. While, the distribution of dominant bacteria Actinobacteria and Verrucomicrobia in water body showed significant seasonal differences. Microbial networks analysis indicated that there was a cooperative symbiotic relationship between lake microbial communities. Notably, the same bacterial genus had no significant positive correlation in sediment and water, which suggested that bacteria transport between sediment-water interface does not influence the microecological functions of lake water.

Response of rotating biological contactor started up by heterotrophic nitrification-aerobic denitrification bacteria to various C/N ratios.

To improve the low pollutant removal efficiency of traditional biological methods for treating livestock and poultry breeding wastewater under a relatively low temperature, a rotating biological contactor (RBC) inoculated with heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria was designed. A quick start-up process and a well removal performance had been achieved in the novel RBC. To elucidate the anti-load shock ability of the novel RBC, the effects of C/N ratio on nitrogen removal and microbial assemblage were focused under a low temperature (12 ± 2 °C). Results showed that the highest NH4+-N and TN removal efficiency were 99.57 ± 0.31% and 68.41 ± 0.52%. Microbial diversity analysis based on high throughput sequencing technique showed that Arcobacter and Flavobacterium with an increasing relative abundance were the key to ensure high nitrogen removal efficiently at a low C/N ratio and temperature. Moreover, nitrogen transferring pathways of the novel RBC was revealed and dissimilatory nitrate reduction and denitrification were the main pathways. The excellent pollutant removal performance demonstrates that the novel RBC is a promising process to effectively treat wastewater with low C/N ratio and low temperature.

Direct aerobic oxidation (DAO) of chlorinated aliphatic hydrocarbons: A review of key DAO bacteria, biometabolic pathways and in-situ bioremediation potential.

Contamination of aquifers and vadose zones with chlorinated aliphatic hydrocarbons (CAH) is a world-wide issue. Unlike other reactions, direct aerobic oxidation (DAO) of CAHs does not require growth substrates and avoids the generation of toxic by-products. Here, we critically review the current understanding of chlorinated aliphatic hydrocarbons-DAO and its application in bioreactors and at the field scale. According to reports on chlorinated aliphatic hydrocarbons-DAO bacteria, isolates mainly consisted of Methylobacterium and Proteobacterium. Chlorinated aliphatic hydrocarbons-DAO bacteria are characterized by tolerance to a high concentration of CAHs and highly efficient removal of CAHs. Trans-1,2-dichloroethylene (t-DCE) is easily transformed biomass for bacteria, followed by 1,2-dichloroethane (1,2-DCA), dichloromethane (DCM), vinyl chloride (VC) and cis-1,2-dichloroethylene (c-DCE). Significant differences in the maximum specific growth rates were observed with different CAHs and biometabolic pathways for DCM, 1,2-DCA, VC and c-DCE degradation have been successfully parsed. Detection of the functional genes etnC and etnE is useful for the determination of active VC DAO bacteria. Additionally, DAO bacteria have been successfully applied to CAHs in new types of bioreactors with satisfactory results. To the best of the authors' knowledge, only one study on DAO-CAHs was conducted in-situ and resulted in 99% CAH removal. Lastly, we put forward future development prospect of chlorinated aliphatic hydrocarbons-DAO.

Characterization of a novel salt-tolerant strain Sphingopyxis sp. CY-10 capable of heterotrophic nitrification and aerobic denitrification.

A novel heterotrophic nitrification and aerobic denitrification (HN-AD) strain CY-10 was isolated and identified as Sphingopyxis sp. When ammonium, nitrate or nitrite was used as the sole nitrogen source (300 mg/L), the maximum nitrogen removal efficiency of strain CY-10 were 100%, 91.1% and 68.5%, respectively. The optimal salinity for ammonia nitrogen removal by strain CY-10 was in the range of 0-5%. At the salinity of 5%, a maximum nitrogen removal rate of 6.25 mg/(L·h) was realized. Metabonomics data showed that the metabolic levels of sucrose and D-tagatose increased significantly at 5% salinity condition, enabling the strain to regulate osmotic pressure and survive in high-salt environments. Functional genes were successfully amplified by quantitative PCR, and HN-AD pathway of strain CY-10 followed NH4+-N â†’ NH2OH â†’ NO2--N â†’ NO â†’ N2O â†’ N2. These findings show that strain CY-10 has great potential in nitrogen removal treatment of saline wastewater.