Thauera lacus sp. nov., isolated from a saline lake in Inner Mongolia.

A Gram-stain-negative, facultatively anaerobic, motile and rod-shaped bacterium, designated D20T, was isolated from the saline Lake Dai in Inner Mongolia, PR China. Growth of strain D20T occurred at 25-45 °C (optimum, 40 °C), pH 4.0-12.0 (optimum, 8.0) and with 0-3 % NaCl (w/v); (optimum, 0-1 %). The results of 16S rRNA gene sequence analysis revealed that strain D20T was most closely related to three Thauera species, Thaueraselenatis AXT, Thaueraaminoaromatica S2T and Thaueraaromatica K172T, with a similarity value of 96.2 %. The major respiratory quinone of strain D20T was ubiquinone-8 (Q-8), and the dominant fatty acids (>10 %) were summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c; 39.8 %), C16 : 0 (30.9 %) and summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c; 13.5 %). The polar lipid profile contained phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, one aminophospholipid and five unidentified lipids. The DNA G+C content was 67.2 mol% (data from the genome sequence). The estimated genome size was 3.7 Mb. The phenotypic, genotypic and chemotaxonomic differences between strain D20T and its phylogenetic relatives indicated that strain D20T should be regarded as a novel species in the genus Thauera, for which the name Thaueralacus sp. nov. is proposed. The type strain is D20T (=MCCC 1H00305T=KCTC 62586T).

Thauera hydrothermalis sp. nov., a thermophilic bacterium isolated from hot spring.

A Gram-stain-negative, non-spore-forming, rod-shaped, motile bacterial strain, designated GD-2T, was isolated from a sediment sample collected from a hot spring in the Tibet Autonomous Region, China. Strain GD-2T grew at a temperature range of 37-55 °C (optimum, 45-50 °C), a pH range of 5.5-11.0 (pH 7.0-7.5) and a NaCl concentration range of 0-4.0 % (0 %). The phylogenetic analysis based on 16S rRNA gene sequencing showed that strain GD-2T represented a member of the genus Thauera within the family Zoogloeaceae. Strain GD-2T was closely related to Thauera linaloolentis 47LolT with the highest 16S rRNA gene sequence similarity of 95.5 %. The whole genomic average nucleotide identity value for GD-2T and 47LolT was 75.3 %. The predominant cellular fatty acids of the strain were C16 : 0, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c), C10 : 0 3-OH and C12 : 0. The main polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, three unidentified phospholipids and two unidentified aminolipids. The major isoprenoid quinone was ubiquinone 8. Genome sequencing revealed that the genome size of GD-2T was 3 059 321 bp with a G+C content of 63.57 mol%. On the basis of phylogenetic, phenotypic and chemotaxonomic characteristics, strain GD-2T is considered to represent a novel species of the genus Thauera, for which the name Thauera hydrothermalis sp. nov. is proposed. The type strain is GD-2T (=NBRC 112472T=CGMCC 1.15527T).

Thauera propionica sp. nov., isolated from downstream sediment sample of the river Ganges, Kanpur, India.

A Gram-stain-negative, non-endospore-producing, short-rod strain, KNDSS-Mac4T, was isolated from a downstream sediment sample of the river Ganges, Kanpur, India and studied by using the polyphasic taxonomic approach. 16S rRNA gene sequence analysis uncovered that the strain had similarity to species of the genus Thauera and formed a distinct phylogenetic cluster with Thauera humireducens KACC16524T. However, KNDSS-Mac4T showed closest phylogenetic affiliation to Thauera aminoaromatica DSM 14742T with 16S rRNA gene sequence similarity of 98.7 % followed by Thauera phenylacetica DSM 14743T (98.6 %), Thauera chlorobenzoica (98.2 %), T. humireducens KACC16524T (98.2 %), Thauera selenatis ATCC 55363T (98.2 %) and Thauera mechernichensis DSM 12266T (98.0 %). The digital DNA-DNA hybridization and average nucleotide identity values between strain KNDSS-Mac4T and the two most closely related taxa, T. aminoaromatica DSM 14742T and T. phenylacetica DSM 14743T, were 26.0, 26.7 and 84.0, 84.3 % respectively. Major lipids present were phosphatidylglycerol, three unknown aminophospholipids, phosphatidylmethylethanolamine, two unidentified lipids and Q-8 as the only ubiquonone. The major cellular fatty acids present were C16 : 1 ω6c/C16 : 1ω7c and C16 : 0. The DNA G+C content of strain KNDSS-Mac4T was 65.9 %. Based on data from phenotypic tests and the genotypic differences of strain KNDSS-Mac4T from its closest phylogenetic relatives, it is evident that this isolate should be regarded as a new species. It is proposed that strain KNDSS-Mac4T should be classified in the genus Thauera as a novel species, Thauerapropionica sp. nov. The type strain is KNDSS-Mac4T (=KCTC 52820T=VTCC-B-910017T).

Thauera sinica sp. nov., a phenol derivative-degrading bacterium isolated from activated sludge.

A bacterial strain, K11T, capable of degrading phenol derivatives was isolated from activated sludge of a sewage treatment plant in China. This strain, which can degrade more than ten phenol derivatives, was identified as a Gram-stain negative, rod-shaped, asporogenous, facultative anaerobic bacterium with a polar flagellum. The strain was found to grow in tryptic soy broth in the presence of 0-2.5% (w/v) NaCl (optimum 0-1%), at 4-43 °C (optimum 30-35 °C) and pH 4.5-10.5 (optimum 7.5-8). Comparative analysis of nearly full-length 16S rRNA gene sequences showed that this strain belongs to the genus Thauera. The 16S rRNA gene sequence was found to show high similarity (97.5%) to that of Thauera chlorobenzoica 3CB-1T, with lesser similarity to other recognised Thauera strains. The G+C content of the DNA of the strain was determined to be 67.8 mol%. The DNA-DNA hybridization value between K11T and Thauera aromatica DSM6984T was 10.4 ± 4.5%. The genomic OrthoANI values of K11T with the other nine type strains of genus Thauera were less than 81.1%. Chemotaxonomic analysis of strain K11T revealed that Q-8 is the predominant quinone; the polar lipids contain phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids and five uncharacterised lipids; the major cellular fatty acid was identified as summed feature 3 (C16:1 ω7c and/or iso-C15:0 2-OH; 45.9%), followed by C16:0 (20.5%) and C18:1 ω7c (15.8%). Based on the phenotypic and phylogenetic evidence, DNA-DNA hybridisation, OrthoANI, chemotaxonomic analysis and results of the physiological and biochemical tests, a new species named Thauera sinica sp. nov. is proposed with strain K11T (= CGMCC 1.15731T = KACC 19216T) designated as the type strain.

Anaerobic degradation of 2,4-dichlorophenoxyacetic acid by Thauera sp. DKT.

Thauera sp. strain DKT isolated from sediment utilized 2,4-dichlorophenoxyacetic acid (2,4D) and its relative compounds as sole carbon and energy sources under anaerobic conditions and used nitrate as an electron acceptor. The determination of 2,4D utilization at different concentrations showed that the utilization curve fitted well with the Edward model with the maximum degradation rate as 0.017 ± 0.002 mM/day. The supplementation of cosubstrates (glucose, acetate, sucrose, humate and succinate) increased the degradation rates of all tested chemical substrates in both liquid and sediment slurry media. Thauera sp. strain DKT transformed 2,4D to 2,4-dichlorophenol (2,4DCP) through reductive side-chain removal then dechlorinated 2,4DCP to 2-chlorophenol (2CP), 4-chlorophenol (4CP) and phenol before complete degradation. The relative degradation rates by the isolate in liquid media were: phenol > 2,4DCP > 2CP > 4CP > 2,4D ≈ 3CP. DKT augmentation in sediment slurry enhanced the degradation rates of 2,4D and chlorophenols. The anaerobic degradation rates in the slurry were significantly slower compared to the rates in liquid media.

Thauera phenolivorans sp. nov., a phenol degrading bacterium isolated from activated sludge.

A Gram-stain negative, short rod-shaped and non-motile bacterial strain ZV1CT 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 C16:1 ω7c /C16:1 ω6c and C16:0. The 16S rRNA gene sequence of stain ZV1CT is phylogenetically related to the 16S rRNA genes of the type strains of Thauera species (similarity: 96.6-97.7%). The genome of strain ZV1CT was sequenced and the size of the genome is 3.68 Mb. The genomic DNA G+C content is 68.2 mol %. Strain ZV1CT exhibited whole-genome average nucleotide identity values of 82.3, 81.5 and 80.9% with respect to Thauera phenylacetica B4PT, Thauera aminoaromatica S2T and Thauera selenatis AXT, respectively. Accordingly, the genome-to-genome distances between strain ZV1CT and the type strains ranged from 21.5 to 31.3%. Based on the results of this study, it is proposed that strain ZV1CT represents a novel species of the genus Thauera, for which the name Thauera phenolivorans is proposed. The type strain is ZV1CT (=CGMCC 1.15497 = NCBR 112379).

Mechanisms and microbial structure of partial denitrification with high nitrite accumulation.

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.

Reconstructing a Thauera genome from a hydrogenotrophic-denitrifying consortium using metagenomic sequence data.

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.

Thauera humireducens sp. nov., a humus-reducing bacterium isolated from a microbial fuel cell.

A Gram-negative, rod-shaped, non-spore-forming bacterium, designated SgZ-1(T), was isolated from the anode biofilm of a microbial fuel cell. The strain had the ability to grow under anaerobic condition via the oxidation of various organic compounds coupled to the reduction of anthraquione-2,6-disulfonate (AQDS) to anthrahydroquinone-2,6-disulfonate (AHQDS). Growth occurred in TSB in the presence of 0-5.5 % (w/v) NaCl (optimum 0-1 %), at 10-45 °C (optimum 25-37 °C) and at pH 6.0-10.0 (optimum 8.0-8.5). Based on 16S rRNA gene sequence similarity, strain SgZ-1(T) belonged to the genus Thauera. The highest level of 16S rRNA gene sequences similarity (96.7 %) was found to be with Thauera aminoaromatica S2(T) and Thauera selenatis AX(T), and lower values were obtained when compared with other recognized Thauera species. Chemotaxonomic analysis revealed that strain SgZ-1(T) contained Q-8 as the predominant quinone, and putrescine and 2-hydroxyputrescine as the major polyamines. The major cellular fatty acids (>5 %) were C16 : 1ω6c and/or C16 : 1ω7c (44.6 %), C16 : 0 (18.8 %), and C18 : 1ω6c and/or C18 : 1ω7c (12.7 %). Based on its phenotypic and phylogenetic properties, chemotaxonomic analysis and the results of physiological and biochemical tests, strain SgZ-1(T) ( = KACC 16524(T) = CCTCC M 2011497(T)) was designated the type strain of a novel species of the genus Thauera, for which the name Thauera humireducens sp. nov. was proposed.

Geomicrobiological properties of ultra-deep granitic groundwater from the Mizunami Underground Research Laboratory (MIU), central Japan.

Although deep subterranean crystalline rocks are known to harbor microbial ecosystems, geochemical factors that constrain the biomass, diversity, and metabolic activities of microorganisms remain to be clearly defined. To better understand the geochemical and microbiological relationships, we characterized granitic groundwater collected from a 1,148- to 1,169-m-deep borehole interval at the Mizunami Underground Research Laboratory site, Japan, in 2005 and 2008. Geochemical analyses of the groundwater samples indicated that major electron acceptors, such as NO(3)(-) and SO(4)(2-), were not abundant, while dissolved organic carbon (not including organic acids), CH(4) and H(2), was moderately rich in the groundwater sample collected in 2008. The total number of acridine orange-stained cells in groundwater samples collected in 2005 and 2008 were 1.1 x 10(4) and 5.2 x 10(4) cells/mL, respectively. In 2005 and 2008, the most common phylotypes determined by 16S rRNA gene sequence analysis were both related to Thauera spp., the cultivated members of which can utilize minor electron donors, such as aromatic and aliphatic hydrocarbons. After a 3-5-week incubation period with potential electron donors (organic acids or CH(4) + H(2)) and with/without electron acceptors (O(2) or NO(3)(-)), dominant microbial populations shifted to Brevundimonas spp. These geomicrobiological results suggest that deep granitic groundwater has been stably colonized by Thauera spp. probably owing to the limitation of O(2), NO(3)(-), and organic acids.

Versatile aromatic compound-degrading capacity and microdiversity of Thauera strains isolated from a coking wastewater treatment bioreactor.

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.

Monitoring the bacterial community dynamics in a petroleum refinery wastewater membrane bioreactor fed with a high phenolic load.

The phenolic compounds are a major contaminant class often found in industrial wastewaters and the biological treatment is an alternative tool commonly employed for their removal. In this sense, monitoring microbial community dynamics is crucial for a successful wastewater treatment. This work aimed to monitor the structure and activity of the bacterial community during the operation of a laboratory-scale continuous submerged membrane bioreactor (SMBR), using PCR and RT-PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA libraries. Multivariate analyses carried out using DGGE profiles showed significant changes in the total and metabolically active dominant community members during the 4-week treatment period, explained mainly by phenol and ammonium input. Gene libraries were assembled using 16S rDNA and 16S rRNA PCR products from the fourth week of treatment. Sequencing and phylogenetic analyses of clones from 16S rDNA library revealed a high diversity of taxa for the total bacterial community, with predominance of Thauera genus (ca. 50%). On the other hand, a lower diversity was found for metabolically active bacteria, which were mostly represented by members of Betaproteobacteria (Thauera and Comamonas), suggesting that these groups have a relevant role in the phenol degradation during the final phase of the SMBR operation.

Development of group-specific PCR-DGGE fingerprinting for monitoring structural changes of Thauera spp. in an industrial wastewater treatment plant responding to operational perturbations.

A Thauera-specific nested-PCR denaturing gradient gel electrophoresis (DGGE) method was developed, and its usefulness was demonstrated by monitoring the structural shifts of Thauera spp. in an anaerobic-anoxic-oxic fixed-biofilm coking wastewater treatment plant (WWTP) responding to operational perturbations. The specificity of the PCR method was confirmed by the fact that all 16 S rRNA gene sequences, cloned from the amplicons of a biofilm sample, belonged to Thauera genus. 16 S rRNA gene V3 region was then amplified from the first round Thauera-specific PCR product and applied for DGGE analysis. All Thauera clones, with 13 different V3 regions, migrated into 10 positions on DGGE gel, which demonstrated the high resolution of this DGGE method. When the WWTP experienced a gradual deterioration in chemical oxygen demand (COD) removal function due to a mechanical failure of the recirculation pump, biofilm samples were collected from the reactor and analyzed by this method. Principal component analysis (PCA) of the DGGE fingerprinting data showed that the composition of Thauera group exhibited a time related trajectory when the plant's COD removal rate decreased from 84.1+/-2.7% in the first 4 weeks to less than 75% at week 5 and 6, suggesting a concomitant shift of Thauera composition and the system's COD removal function. This group-specific PCR DGGE fingerprinting technology has the potential to be a profiling tool for monitoring structural shifts of Thauera spp. in industrial WWTPs.

[Specific-PCR and denaturing gradient gel electrophoresis assistant isolation of Thauera spp. from a coking wastewater treatment plant].

OBJECTIVE: We used specific-PCR and denaturing gradient gel electrophoresis (DGGE) to isolate Thauera spp. from a coking wastewater treatment plant. METHODS AND RESULTS: To isolate Thauera from the denitrifying bioreactor of a coking wastewater treatment, biofilm was inoculated to six different media and cultured them under both aerobic and anaerobic conditions. We then compared the composition of Thauera spp. using Thauera-specific PCR-DGGE method. The media 1/10 NB and MMQ which grew higher diverse Thauera spp. and fewer colonies, were used to isolate Thauera sp. under aerobic condition. The colonies were then screened by Thauera-specific PCR. The purity of the colonies that shown Thauera-specific PCR positive signal was then checked by DGGE. The colonies with multiple species were further streaked on different media. DGGE analysis showed that Thauera in colony Q20 was enriched in medium MMP. The colony was finally purified by streaking on MMP medium for several rounds. The composition of the colonies were tracked by Thauera-specific PCR and DGGE at each step. Finally, three strains were purified, which were identified as Thauera sp. according to their 16S rRNA gene sequences. CONCLUSION: Guiding with specific biomarker, the efficiency and sensitivity of bacteria isolation can be largely improved.

Environmental fate of endocrine-disrupting dimethyl phthalate esters (DMPE) under sulfate-reducing condition.

Dimethyl phthalate esters (DMPE) can easily be released into the environment from plastic products. As endocrine disruptors, DMPE mimic estrogenic activities in animals and humans. The metabolites of DMPE are suspected to cause even more serious health problems. Among the common sterilization techniques adopted in the study of DMPE degradation, the average loss of the parent DMPE compounds after autoclaving was as high as 21.26%. In contrast, the loss after 0.2 microm filtration was significantly lower at 2.28%. It is suggested that filtration should be used over autoclaving for sterilizing DMPE. The environmental fate of DMPE under sulfate-reducing condition was simulated and studied in microcosm system. It was observed that dimethyl phthalate (DMP), dimethyl isophthalate (DMI) and dimethyl terephthalate (DMT) could not be mineralized over an extended period of 6 months, but with the transformation to the respective monomethyl phthalate and/or phthalic acid. The dominant species of microorganisms utilizing individual DMPE isomer as the sole carbon source were isolated and identified as facultative anaerobe Thauera sp., Xanthobacter sp. and Agrobacterium sp. for DMP, DMI and DMT, respectively. This study illustrates that the detrimental DMPE and their natural metabolites may accumulate in the sulfate-reducing environment. Accordingly, proper surveillance program should be devised to monitor both the parent compounds and degradation intermediates of DMPE in order to protect the aquatic ecosystem and human health.

Thauera and Azoarcus as functionally important genera in a denitrifying quinoline-removal bioreactor as revealed by microbial community structure comparison.

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 non-efficient 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.

Characterization of Thauera-dominated hydrogen-oxidizing autotrophic denitrifying microbial communities by using high-throughput sequencing.

The present study, for the first time, reported a Thauera-dominated hydrogen-oxidizing autotrophic denitrifying microbial community enriched from different seed sludges including activated sludge and anaerobic digestion sludge. After 244 days enrichment, nitrogen removal rates reached up to 0.2 mg N/mg VSS/d which were comparable to that of the model organism Paracoccus denitrificans under the same conditions. Furthermore, high-throughput sequencing was applied to characterize and compare the seed sludges and enriched cultures. Operational taxonomic units (OTU)-based analysis (97% similarity cutoff) of total 280,000 16S rRNA gene V6 region sequences from 7 sludge samples (40,000 sequences per sample) revealed that the microbial diversity decreased after the enrichment, indicated by OTU numbers drop of 55-60%. Thauera species in the class of ß-Proteobacteria were enriched into the dominant populations with relative abundances of 47-62%, regardless of seed sludge sources.

Reactor performance in terms of COD and nitrogen removal and bacterial community structure of a three-stage rotating bioelectrochemical contactor.

Integrating microbial fuel cell (MFC) into rotating biological contactor (RBC) creates an opportunity for enhanced removal of COD and nitrogen coupled with energy generation from wastewater. In this study, a three-stage rotating bioelectrochemical contactor (referred to as RBC-MFC unit) integrating MFC with RBC technology was constructed for simultaneous removal of carbonaceous and nitrogenous compounds and electricity generation from a synthetic medium containing acetate and ammonium. The performance of the RBC-MFC unit was compared to a control reactor (referred to as RBC unit) that was operated under the same conditions but without current generation (i.e. open-circuit mode). The effect of hydraulic loading rate (HLR) and COD/N ratio on the performance of the two units was investigated. At low (3.05 gCOD g⁻¹N) and high COD/N ratio (6.64 gCOD g⁻¹N), both units achieved almost similar COD and ammonia-nitrogen removal. However, the RBC-MFC unit achieved significantly higher denitrification and nitrogen removal compared to the RBC unit indicating improved denitrification at the cathode due to current flow. The average voltage under 1000 Ω external resistance ranged between 0.03 and 0.30 V and between 0.02 and 0.21 V for stages 1 and 2 of the RBC-MFC unit. Pyrosequencing analysis of bacterial 16S rRNA gene revealed high bacterial diversity at the anode and cathode of both units. Genera that play a role in nitrification (Nitrospira; Nitrosomonas), denitrification (Comamonas; Thauera) and electricity generation (Geobacter) were identified at the electrodes. Geobacter was only detected on the anode of the RBC-MFC unit. Nitrifiers and denitrifiers were more abundant in the RBC-MFC unit compared to the RBC unit and were largely present on the cathode of both units suggesting that most of the nitrogen removal occurred at the cathode.

Thauera butanivorans sp. nov., a C2-C9 alkane-oxidizing bacterium previously referred to as 'Pseudomonas butanovora'.

The placement of 'Pseudomonas butanovora' in the genus Thauera was proposed previously, based on 16S rRNA gene sequence analysis, upon further studies of taxonomical characteristics. In this study, physiological characteristics and DNA-DNA reassociation data are presented and the transfer of 'P. butanovora' to the genus Thauera is proposed. The original description of the strain (strain Bu-B1211) indicated that it was capable of denitrification but not anaerobic growth. 'P. butanovora' is capable of anaerobic respiration and growth, utilizing nitrate as a terminal electron acceptor during the oxidation of organic acids and alcohols, but not aromatic hydrocarbons or open-chain terpenoids. The total fatty acid composition supported the assignment of strain Bu-B1211 to the Betaproteobacteria and resembled that of members of the genus Thauera. The combination of 16S rRNA gene phylogenetic evidence, physiological and taxonomical characteristics and DNA-DNA reassociation data supported the placement of 'Pseudomonas butanovora' Bu-B1211 in the genus Thauera as representing a novel species, for which the name Thauera butanivorans sp. nov. is proposed. The type strain is Bu-B1211(T) (=IAM 12574(T)=ATCC 43655(T)=DSM 2080(T)).