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A Gram-stain negative, short rod-shaped and non-motile bacterial strain ZV1C T capable of degrading phenol was isolated from a wastewater treatment system of Huafu mustard tuber salinity preservation factory in Chongqing, China. Aerobic growth was observed at 20–42 °C (optimum, 30 °C) and at pH 5–10 (optimum, pH 8). Cells tolerated NaCl concentrations of 0–2% (w/v) (optimum, 0%). The major respiratory quinone is ubiquinone Q-8 and the major cellular fatty acids are C 16:1 ω7c /C 16:1 ω6c and C 16:0 . The 16S rRNA gene sequence of stain ZV1C T is phylogenetically related to the 16S rRNA genes of the type strains of Thauera species (similarity: 96.6–97.7%). The genome of strain ZV1C T was sequenced and the size of the genome is 3.68 Mb. The genomic DNA G+C content is 68.2 mol %. Strain ZV1C T exhibited whole-genome average nucleotide identity values of 82.3, 81.5 and 80.9% with respect to Thauera phenylacetica B4P T , Thauera aminoaromatica S2 T and Thauera selenatis AX T , respectively. Accordingly, the genome-to-genome distances between strain ZV1C T and the type strains ranged from 21.5 to 31.3%. Based on the results of this study, it is proposed that strain ZV1C T represents a novel species of the genus Thauera , for which the name Thauera phenolivorans is proposed. The type strain is ZV1C T (=CGMCC 1.15497 = NCBR 112379).

Nitrite (NO₂ ⁻-N) accumulation in denitrification can provide the substrate for anammox, an efficient and cost-saving process for nitrogen removal from wastewater. This batch-mode study aimed at achieving high NO₂ ⁻-N accumulation over long-term operation with the acetate as sole organic carbon source and elucidating the mechanisms of NO₂ ⁻-N accumulation. The results showed that the specific nitrate (NO₃ ⁻-N) reduction rate (59.61 mg N VSS⁻¹ h⁻¹ at NO₃ ⁻-N of 20 mg/L) was much higher than specific NO₂ ⁻-N reduction rate (7.30 mg N VSS⁻¹ h⁻¹ at NO₃ ⁻-N of 20 mg/L), and the NO₂ ⁻-N accumulation proceeded well at the NO₃ ⁻-N to NO₂ ⁻-N transformation ratio (NTR) as high as 90 %. NO₂ ⁻-N accumulation was barely affected by the ratio of chemical oxygen demand (COD) to NO₃ ⁻-N concentration (C/N). With the addition of NO₃ ⁻-N, NO₂ ⁻-N accumulation occurred and the specific NO₂ ⁻-N reduction rate declined to a much lower level compared with the value in the absence of NO₃ ⁻-N. This indicated that the denitrifying bacteria in the system preferred to use NO₃ ⁻-N as electron acceptor rather than use NO₂ ⁻-N. In addition, the Illumina high-throughput sequencing analysis revealed that the genus of Thauera bacteria was dominant in the denitrifying community with high NO₂ ⁻-N accumulation and account for 67.25 % of total microorganism. This bacterium might be functional for high NO₂ ⁻-N accumulation in the presence of NO₃ ⁻-N.

During selenate respiration by Thauera selenatis, the reduction of selenate results in the formation of intracellular selenium (Se) deposits that are ultimately secreted as Se nanospheres of approximately 150 nm in diameter. We report that the Se nanospheres are associated with a protein of approximately 95 kDa. Subsequent experiments to investigate the expression and secretion profile of this protein have demonstrated that it is up-regulated and secreted in response to increasing selenite concentrations. The protein was purified from Se nanospheres, and peptide fragments from a tryptic digest were used to identify the gene in the draft T. selenatis genome. A matched open reading frame was located, encoding a protein with a calculated mass of 94.5 kDa. N-terminal sequence analysis of the mature protein revealed no cleavable signal peptide, suggesting that the protein is exported directly from the cytoplasm. The protein has been called Se factor A (SefA), and homologues of known function have not been reported previously. The sefA gene was cloned and expressed in Escherichia coli, and the recombinant His-tagged SefA purified. In vivo experiments demonstrate that SefA forms larger (approximately 300 nm) Se nanospheres in E. coli when treated with selenite, and these are retained within the cell. In vitro assays demonstrate that the formation of Se nanospheres upon the reduction of selenite by glutathione are stabilized by the presence of SefA. The role of SefA in selenium nanosphere assembly has potential for exploitation in bionanomaterial fabrication.

Here, shotgun metagenomic sequencing was conducted to reveal the hydrogen-oxidizing autotrophic-denitrifying metabolism in an enriched Thauera-dominated consortium. A draft genome named Thauera R4 of over 90 % completeness (3.8 Mb) was retrieved mainly by a coverage-defined binning method from 3.5 Gb paired-end Illumina reads. We identified 1,263 genes (accounting for 33 % of total genes in the finished genome of Thauera aminoaromatica MZ1T) with average nucleotide identity of 87.6 % shared between Thauera R4 and T. aminoaromatica MZ1T. Although Thauera R4 and T. aminoaromatica shared quite similar nitrogen metabolism and a high nucleotide similarity (98.8 %) in their 16S ribosomal RNA genes, they showed different functional potentials in several important environmentally relevant processes. Unlike T. aminoaromatica MZ1T, Thauera R4 carries an operon of [NiFe]-hydrogenase (EC 1.12.99.6) catalyzing molecular hydrogen oxidation in nitrate-rich solution. Moreover, Thauera R4 is a mixtrophic bacterium possessing key enzymes for autotrophic CO₂-fixation and heterotrophic acetate assimilation metabolism. This Thauera R4 bin provides another genetic reference to better understand the niches of Thauera and demonstrates a model pipeline to reveal functional profiles and reconstruct novel and dominant genomes from a simplified mixed culture in environmental studies.

ABSTRACT Nitrous oxide (N2O) is a potent greenhouse gas and its reduction to dinitrogen gas by the N2O reductase (encoded by the nosZ gene) is the only known biological N2O sink. Within the nosZ phylogeny there are two major clades (I and II), which seem to have different ecological niches. However, physiological differences of nosZI and nosZII expression that may impact emissions of N2O are not well understood. Here, we evaluated the differential expression of nosZI and nosZII, both present in Thauera linaloolentis strain 47LolT, in response to N2O concentration and the presence of the competing electron acceptor nitrate (NO3−). Different N2O levels had a negligible effect on the expression of both nosZ clades. Interestingly, nosZII expression was strongly upregulated in the absence of NO3−, while nosZI expression remained constant across the conditions tested. Thus, NO3− possibly inhibited nosZII expression, which suggests that N2O mitigation mediated by nosZII can be restricted due to the presence of NO3− in the environment. This is the first study demonstrating differential expression of nosZI and nosZII genes under the same physiological conditions and their implications for N2O emission under varying environmental conditions in terms of NO3− availability. Thauera linaloolentis carries two nosZ genotypes (clade I and II) which are differentially regulated by nitrate.

Bacteria of the Thauera genus have been described as important aromatic compound degraders and have attracted increased attention. In this study, three Thauera strains (Q4, Q20-C, and 3-35) were isolated from a coking wastewater treatment plant (WWTP) with a high abundance of Thauera. The 16S rRNA, nitrite reductase, and phenol hydroxylase (LmPH) genes and pollutant-degrading capacity of these strains were characterized and compared. Their 16S rRNA gene sequences were identical, but the genomic structures differed, as demonstrated by distinct enterobacterial repetitive intergenic consensus sequence PCR profiles with a similarity of less than 0.65. The analysis of degradation of coking wastewater by these strains showed that most of the main organic pollutants—phenol, methylphenol, and indole, but not quinoline—were degraded under aerobic conditions. These strains contained different LmPHs genes and showed different phenol degradation rates (Q4 > 3-35 > Q20-C). The presence of a microdiversity of Thauera spp. implies the existence of various finely differentiated niches in the industrial WWTP. The capacity of the Thauera strains to degrade a wide spectrum of aromatic compounds suggests their potential in bioremediation applications targeting aromatic pollutant-containing wastewater.

Microbial denitrification is the main pathway for nitrogen removal of landfill leachate. Although humic substances (HSs) have been reported in landfill leachate, the effects of HS on denitrification process of activated sludge for leachate treatment are still unknown. In this study, we adopted SAHA as the model HS to study the effects of HS on the denitrification of landfill leachate. After long-term operation at 10 mg/L of Shanghai Aladdin Humic Acid (SAHA), the final nitrate concentration and nitrite accumulation were much lower than the control (5.2 versus 96.2 mg/L; 0.5 versus 34.7 mg/L), and the final N 2 O emission was 13.1% of the control. The mechanistic study unveiled that SAHA substantially changed the activated sludge community structure and resulted in the dominance of Thauera after long-term exposure to SAHA. Thauera could be able to utilize HSs as electron shuttle to improve denitrificattion performance, especially for nitrite reduction. Moreover, SAHA significantly upregulated the gene expressions and catalytic activities of the key enzymes related to denitrification, the reducing power (NADH) generation, and the electron transport system activity, which accelerated nitrogen oxide reduction. The positive effects of HS on denitrification performance were confirmed by the addition of SAHA into real leachate.

The denitrifying bacterium Thauera sp . MZ1T, a common member of microbial communities in wastewater treatment facilities, can produce different compounds from a range of carbon (C) and nitrogen (N) sources under aerobic and anaerobic conditions. In these different conditions, Thauera modifies its metabolism to produce different compounds that influence the microbial community. In particular, Thauera sp . MZ1T produces different exopolysaccharides with floc-forming properties, impacting the physical disposition of wastewater consortia and the efficiency of nutrient assimilation by the microbial community. Under N-limiting conditions, Thauera sp . MZ1T decreases its growth rate and accelerates the accumulation of polyhydroxyalkanoate-related (PHA) compounds including polyhydroxybutyrate (PHB), which plays a fundamental role as C and energy storage in this β-proteobacterium. However, the metabolic mechanisms employed by Thauera sp . MZ1T to assimilate and catabolize many of the different C and N sources under aerobic and anaerobic conditions remain unknown. Systems biology approaches such as genome-scale metabolic modeling have been successfully used to unveil complex metabolic mechanisms for various microorganisms. Here, we developed a comprehensive metabolic model (M-model) for Thauera sp . MZ1T ( i Thauera861), consisting of 1,744 metabolites, 2,384 reactions, and 861 genes. We validated the model experimentally using over 70 different C and N sources under both aerobic and anaerobic conditions. i Thauera861 achieved a prediction accuracy of 95% for growth on various C and N sources and close to 85% for assimilation of aromatic compounds under denitrifying conditions. The M-model was subsequently deployed to determine the effects of substrates, oxygen presence, and the C:N ratio on the production of PHB and exopolysaccharides (EPS), showing the highest polymer yields are achieved with nucleotides and amino acids under aerobic conditions. This comprehensive M-model will help reveal the metabolic processes by which this ubiquitous species influences communities in wastewater treatment systems and natural environments.

Hydrogen autotrophic reduction of perchlorate have advantages of high removal efficiency and harmless to drinking water. But so far the reported information about the microbial community structure was comparatively limited, changes in the biodiversity and the dominant bacteria during acclimation process required detailed study. In this study, perchlorate-reducing hydrogen autotrophic bacteria were acclimated by hydrogen aeration from activated sludge. For the first time, high-throughput sequencing was applied to analyze changes in biodiversity and the dominant bacteria during acclimation process. The Michaelis–Menten model described the perchlorate reduction kinetics well. Model parameters q max and K s were 2.521–3.245 (mg ClO 4 − /gVSS h) and 5.44–8.23 (mg/l), respectively. Microbial perchlorate reduction occurred across at pH range 5.0–11.0; removal was highest at pH 9.0. The enriched mixed bacteria could use perchlorate, nitrate and sulfate as electron accepter, and the sequence of preference was: NO 3 −  > ClO 4 −  > SO 4 2− . Compared to the feed culture, biodiversity decreased greatly during acclimation process, the microbial community structure gradually stabilized after 9 acclimation cycles. The Thauera genus related to Rhodocyclales was the dominated perchlorate reducing bacteria (PRB) in the mixed culture.

Abstract Structural shifts associated with functional dynamics in a bacterial community may provide clues for identifying the most valuable members in an ecosystem. A laboratory-scale denitrifying reactor was adapted from use of nonefficient seeding sludge and was utilized to degrade quinoline and remove the chemical oxygen demand. Stable removal efficiencies were achieved after an adaptation period of six weeks. Both denaturing gradient gel electrophoresis profiling of the 16S rRNA gene V3 region and comparison of the 16S rRNA gene sequence clone libraries (LIBSHUFF analysis) demonstrated that microbial communities in the denitrifying reactor and seeding sludge were significantly distinct. The percentage of the clones affiliated with the genera Thauera and Azoarcus was 74% in the denitrifying reactor and 4% in the seeding sludge. Real-time quantitative PCR also indicated that species of the genera Thauera and Azoarcus increased in abundance by about one order of magnitude during the period of adaptation. The greater abundance of Thauera and Azoarcus in association with higher efficiency after adaptation suggested that these phylotypes might play an important role for quinoline and chemical oxygen demand removal under denitrifying conditions.