Ottowia thiooxydans gen. nov., sp. nov., a novel facultatively anaerobic, N2O-producing bacterium isolated from activated sludge, and transfer of Aquaspirillum gracile to Hylemonella gracilis gen. nov., comb. nov

Exploring the maximum nitrite production rate through the granular sludge-type reactor to match the needs of anammox process realizing efficient nitrogen removal

The reliable and efficient nitrite production rate (NPR) through nitritation process is the prerequisite for the efficient running of subsequent processes, like the anammox process and the nitrite shunt. However, there has been scant research on stable and productive nitritation process in recent years. In this study, at a stable hydraulic retention time of 12.0 h and with precise and strict DO control, the upper limit of the NPR was initially investigated using a continuous-flow granular sludge reactor. The NPR of 1.69 kg/m3/d with a nitrite production efficiency of 81.97% was finally achieved, which set a record until now in similar research. The median sludge particle size of 270.0 μm confirmed the development of clearly defined granular sludge. The genus Nitrosomonas was the major ammonium oxidizing bacteria. In conclusion, this study provides valuable insights for the practical application of the effective nitritation process driving subsequent nitrogen removal processes.

Intermittent hydroxylamine dosing to strengthen stability of partial nitrification and nitrogen removal efficiency through continuous-flow anaerobic-aerobic-anoxic reactor treating municipal wastewater

Intermittent hydroxylamine (NH2OH) dosing strategy was applied to enhance the stability of partial nitrification and total nitrogen (N) removal efficiency (TNRE) in a continuous-flow process. The results showed 2 mg/L of NH2OH dosing (once every 6 h) could maintain stably partial nitrification with nitrite accumulation rate (NAR) of 91.6 % and TNRE of 92.6 %. The typical cycle suggested NH2OH dosing could promote simultaneous nitrification-denitrification (SND) and endogenous denitrification (END) while inhibit exogenous denitrification (EXD). Nitrification characteristics indicated the NH2OH dosing enhanced stability of partial nitrification by suppressing specific nitrite oxidation rate (SNOR), Nitrospira and nitrite oxidoreductase enzyme (Nxr). The microbial community suggested the aerobic denitrfiers, denitrifying glycogen accumulating organisms (DGAOs) and traditional denitrfiers were the potential contributor for advanced N removal. Moreover, NH2OH dosage was positively associated with NAR, SND and END. Overall, this study offers a feasible strategy to maintain sustainably partial nitrification that has great application potential.

Revealing the functional potential of microbial community of activated sludge for treating tuna processing wastewater through metagenomic analysis

Reports regarding the composition and functions of microorganisms in activated sludge from wastewater treatment plants for treating tuna processing wastewater remains scarce, with prevailing studies focusing on municipal and industrial wastewater. This study delves into the efficiency and biological dynamics of activated sludge from tuna processing wastewater, particularly under conditions of high lipid content, for pollutant removal. Through metagenomic analysis, we dissected the structure of microbial community, and its relevant biological functions as well as pathways of nitrogen and lipid metabolism in activated sludge. The findings revealed the presence of 19 phyla, 1,880 genera, and 7,974 species, with Proteobacteria emerging as the predominant phylum. The study assessed the relative abundance of the core microorganisms involved in nitrogen removal, including Thauera sp. MZ1T and Alicycliphilus denitrificans K601, among others. Moreover, the results also suggested that a diverse array of fatty acid-degrading microbes, such as Thauera aminoaromatica and Cupriavidus necator H16, could thrive under lipid-rich conditions. This research can provide some referable information for insights into optimizing the operations of wastewater treatment and identify some potential microbial agents for nitrogen and fatty acid degradation.

Ottowia cancrivicina sp. nov., isolated from human stomach

A Gram-negative, facultative anaerobic, non-motile and rod-shaped bacterium, designated 10c7w1T, was isolated from a human gastrointestinal tract. Colonies on agar plates were small, circular, smooth and beige. The optimal growth conditions were determined to be 37 °C, pH 7.0-7.5 and 0 % (w/v) NaCl. Comparative analysis of complete 16S rRNA gene sequences revealed that strain 10c7w1T showed the highest sequence similarity of 95.8 % to Ottowia beijingensis MCCC 1A01410T, followed by Ottowia thiooxydans (95.2 %) JCM 11629T. The average amino acid identity values between 10c7w1T and O. beijingensis MCCC 1A01410T and O. thiooxydans JCM 11629T were above 60 % (71.4 and 69.5 %). The average nucleotide identity values between strain 10c7w1T and O. beijingensis MCCC 1A01410T and O. thiooxydans JCM 11629T were 76.9 and 72.5 %, respectively. The dominant fatty acids (≥10 %) were straight chain ones, with summed feature 3 (C16 : 1  ω7c/C16 : 1  ω6c), summed feature 8 (C18 : 1  ω7c/C18 : 1  ω6c) and C16 : 00 being the most abundant. Q-8 was the only respiratory quinone. The major polar lipids of strain 10c7w1T were phosphatidylethanolamine, diphosphatidylglycerol and unknown lipids. The DNA G+C content of strain 10c7w1T was 63.6 mol%. On the basis of phylogenetic, phenotypic and chemotaxonomic data, strain 10c7w1T is considered to represent a novel species within the genus Ottowia, for which the name Ottowia cancrivicina sp. nov. is proposed. The type strain is 10c7w1T (=MCCC 1H01399T=KCTC 92200T).

Dynamics of Methane-Consuming Biomes from Wieliczka Formation: Environmental and Enrichment Studies

The rocks surrounding Wieliczka salt deposits are an extreme, deep subsurface ecosystem that as we studied previously harbors many microorganisms, including methanotrophs. In the presented research bacterial community structure of the Wieliczka Salt Mine was determined as well as the methanotrophic activity of the natural microbiome. Finally, an enrichment culture of methane-consuming methanotrophs was obtained. The research material used in this study consisted of rocks surrounding salt deposits in the Wieliczka Salt Mine. DNA was extracted directly from the pristine rock material, as well as from rocks incubated in an atmosphere containing methane and mineral medium, and from a methanotrophic enrichment culture from this ecosystem. As a result, the study describes the composition of the microbiome in the rocks surrounding the salt deposits, while also explaining how biodiversity changes during the enrichment culture of the methanotrophic bacterial community. The contribution of methanotrophic bacteria ranged from 2.614% in the environmental sample to 64.696% in the bacterial culture. The methanotrophic enrichment culture was predominantly composed of methanotrophs from the genera Methylomonas (48.848%) and Methylomicrobium (15.636%) with methane oxidation rates from 3.353 ± 0.105 to 4.200 ± 0.505 µmol CH4 mL-1 day-1.

The Hylemon-Björkhem pathway of bile acid 7-dehydroxylation: history, biochemistry, and microbiology

Bile acids are detergents derived from cholesterol that function to solubilize dietary lipids, remove cholesterol from the body, and act as nutrient signaling molecules in numerous tissues with functions in the liver and gut being the best understood. Studies in the early 20th century established the structures of bile acids, and by mid-century, the application of gnotobiology to bile acids allowed differentiation of host-derived "primary" bile acids from "secondary" bile acids generated by host-associated microbiota. In 1960, radiolabeling studies in rodent models led to determination of the stereochemistry of the bile acid 7-dehydration reaction. A two-step mechanism was proposed, which we have termed the Samuelsson-Bergström model, to explain the formation of deoxycholic acid. Subsequent studies with humans, rodents, and cell extracts of Clostridium scindens VPI 12708 led to the realization that bile acid 7-dehydroxylation is a result of a multi-step, bifurcating pathway that we have named the Hylemon-Björkhem pathway. Due to the importance of hydrophobic secondary bile acids and the increasing measurement of microbial bai genes encoding the enzymes that produce them in stool metagenome studies, it is important to understand their origin.

Low C/N promotes stable partial nitrification by enhancing the cooperation of functional microorganisms in treating high-strength ammonium landfill leachate

Partial nitrification is an effective process for treating high-strength ammonium landfill leachate with low C/N ratio, for the cooperation with denitrification can save almost 40% carbon addition in biological nitrogen removal. However, high ammonia loading often causes the instability of partial nitrification process. Less carbon addition can promote the stability of partial nitrification and increase the nitrite accumulation ratio (NAR). Nevertheless, the microbial mechanisms within remain further elusive. In this study, two laboratory-scale sequencing batch reactors were constructed and operated for 125 days, which were fed with ammonia synthetic wastewater with C/N of 0.6 (CN system) and C/N of 0.0 as the control (N system). CN system performed more stably and had the highest NAR of 100%. Extracellular polymeric substances (EPS) generated from carbon source provided spatial and nutrient niches to tighten the cooperation of functional microorganisms, thus, enhanced the stability and efficiency of partial nitrification. Thauera was the dominant denitrifier in CN system. Nitrosomonas was one of the most important autotrophic ammonia oxidizing bacteria, while Paracoccus and Flavobacterium were the main heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria in CN system. The enrichment of HN-AD bacteria outcompeted nitrite oxidizing bacteria (NOB), therefore leaded to higher nitrite accumulation in CN system. The findings of this study may be conducive to increasing the understanding of the microbial collaboration mechanisms of partial nitrification, thereby provides theoretical support for the improvement of biological nitrogen removal technology.

Exploring the Interspecific Interactions and the Metabolome of the Soil Isolate Hylemonella gracilis

Microbial community analysis of aquatic environments showed that an important component of its microbial diversity consists of bacteria with cell sizes of ~0.1 μm. Such small bacteria can show genomic reductions and metabolic dependencies with other bacteria. However, so far, no study has investigated if such bacteria exist in terrestrial environments like soil. Here, we isolated soil bacteria that passed through a 0.1-μm filter. The complete genome of one of the isolates was sequenced and the bacterium was identified as Hylemonella gracilis. A set of coculture assays with phylogenetically distant soil bacteria with different cell and genome sizes was performed. The coculture assays revealed that H. gracilis grows better when interacting with other soil bacteria like Paenibacillus sp. AD87 and Serratia plymuthica. Transcriptomics and metabolomics showed that H. gracilis was able to change gene expression, behavior, and biochemistry of the interacting bacteria without direct cell-cell contact. Our study indicates that in soil there are bacteria that can pass through a 0.1-μm filter. These bacteria may have been overlooked in previous research on soil microbial communities. Such small bacteria, exemplified here by H. gracilis, can induce transcriptional and metabolomic changes in other bacteria upon their interactions in soil. In vitro, the studied interspecific interactions allowed utilization of growth substrates that could not be utilized by monocultures, suggesting that biochemical interactions between substantially different sized soil bacteria may contribute to the symbiosis of soil bacterial communities. IMPORTANCE Analysis of aquatic microbial communities revealed that parts of its diversity consist of bacteria with cell sizes of ~0.1 μm. Such bacteria can show genomic reductions and metabolic dependencies with other bacteria. So far, no study investigated if such bacteria exist in terrestrial environments such as soil. Here, we show that such bacteria also exist in soil. The isolated bacteria were identified as Hylemonella gracilis. Coculture assays with phylogenetically different soil bacteria revealed that H. gracilis grows better when cocultured with other soil bacteria. Transcriptomics and metabolomics showed that H. gracilis was able to change gene expression, behavior, and biochemistry of the interacting bacteria without direct contact. Our study revealed that bacteria are present in soil that can pass through 0.1-μm filters. Such bacteria may have been overlooked in previous research on soil microbial communities and may contribute to the symbiosis of soil bacterial communities.

A novel multistage anoxic/aerobic process with sludge regeneration zone (R-MAO) for advanced nitrogen removal from domestic sewage

To achieve advanced nitrogen removal from actual municipal sewage, a novel multistage anoxic/aerobic process with sludge regeneration zone (R-MAO) was developed. The reactor was used to treat actual domestic sewage and the nitrogen removal capacity of the sludge regeneration zone (R zone) was investigated during the long-term operation. The best performance was obtained at the R zone's Oxidation-Reduction Potential (ORP) of -50±30 mV and hydraulic residence times (HRT) of 1.2 hr. The average effluent COD, TN, NH₄⁺-N and NO₃^--N of the R-MAO process were 18.0±2.3, 7.5±0.6, 1.0±0.5 and 4.6±0.4 mg/L, respectively, with the corresponding removal efficiency of COD, TN and NH₄⁺-N were 92.9%±1.0%, 84.1%±1.5% and 97.5%±1.1%. Compared to the sole MAO system, the TN removal efficiency of the R-MAO increased by 10.1%. Besides, under the optimal conditions, the contribution of the R zone in the R-MAO that removal COD, TN, NH₄⁺-N and NO₃^--N were 0.36, 0.15, 0.032 and 0.82 g/day. High-throughput sequencing results showed that uncultured_bacterium_f_Burkholderiaceae (5.20%), OLB8 (1.04%) and Ottowia (1.03%) played an important role in denitrification in the R zone. This study provided effective guidance for the design and operation of the R-MAO process in domestic sewage treatment.

Variations in antibiotic resistance genes and microbial community in sludges passing through biological nutrient removal and anaerobic digestion processes in municipal wastewater treatment plants

Antimicrobial resistance (AMR) represents a relentless, silent pandemic. Contributing to this are wastewater treatment plants (WWTPs), a potential source of antibiotic resistance genes' (ARGs) transmission to the environment, threatening public health. The presence of ARGs in pathogenic bacteria and their release into the environment by WWTPs threatens the public health. The current study investigated changes in ARGs' abundance in biological nutrient removal (BNR) processes and anaerobic digestion (AD) reactors of two WWTPs. Also, microbial community structure, which is known to shape the distribution and abundance of ARGs, was also analyzed. The relative abundance of eight ARGs (tetX, tetA, tetM, TEM, sul1, sul2, ermB and qnrD) was quantified as ARGs' copies/16 S rRNA gene copies using quantitative polymerase chain reaction (qPCR). Microbial community composition was assessed by 16 S rRNA microbiome sequencing analysis. TetX was prevalent among the eight ARGs, followed by TEM and sul1. However, its abundance was decreased in the AD sludges compared to BNR sludges. Proteobacteria was the major bacterial phylum found in all the sludge samples, while Arcobacter, 12up and Acidovorax were the predominant genera. Acinetobacter and Flavobacterium were significantly more abundant in the BNR sludges, while 12up and Aeromonas were predominant in AD sludges. Principal component analysis (PCA) revealed a clear difference in dominant ARGs and bacteria between the sludges in the processes of BNR and AD of the two WWTPs. Clinically relevant bacterial genera, Klebsiella and Enterococcus, found in both the BNR and AD sludges, were significantly correlated with the tetX gene. Throughout this study, the relationship between microbial communities and specific ARGs was revealed, illustrating that the composition of the microbial community could play a vital role in the abundance of ARGs. These results will better inform future studies aimed at controlling the spread of ARGs and their potential hosts from WWTPs.

A metabolic puzzle: Consumption of C1 compounds and thiosulfate in Hyphomicrobium denitrificans XT

Many obligately heterotrophic methylotrophs oxidize thiosulfate as an additional electron source during growth on C₁ compounds. Although two different pathways of thiosulfate oxidation are implemented in Hyphomicrobium denitrificans X^T, a pronounced negative effect on growth rate is observed when it is cultured in the simultaneous presence of methanol and thiosulfate. In this model organism, periplasmic thiosulfate dehydrogenase TsdA catalyzes formation of the dead-end product tetrathionate. By reverse genetics we verified the second pathway that also starts in the periplasm where SoxXA catalyzes the oxidative fusion of thiosulfate to SoxYZ, from which sulfate is released by SoxB. Sulfane sulfur is then further oxidized in the cytoplasm by the sulfur-oxidizing heterodisulfide reductase-like system (sHdr) which is produced constitutively in a strain lacking the transcriptional repressor sHdrR. When exposed to thiosulfate, the ΔshdrR strain exhibited a strongly reduced growth rate even without thiosulfate in the pre-cultures. When grown on methanol, cells exhibit significantly increased NAD⁺/NADH ratios in the presence of thiosulfate. In contrast, thiosulfate did not exert any negative effect on growth rate or increase NAD⁺ levels during growth on formate. On both C₁ substrates, excretion of up to 0.5 mM sulfite as an intermediate of thiosulfate (2 mM) oxidation was recorded. Sulfite is known to form adducts with pyrroloquinoline quinone, the cofactor of periplasmic methanol dehydrogenase. We rationalize that this causes specific inhibition of methanol degradation in the presence of thiosulfate while formate metabolism in the cytoplasm remains unaffected.

Perchlorate removal by a combined heterotrophic and bio-electrochemical hydrogen autotrophic system

Here, a novel combined heterotrophic and bio-electrochemical hydrogen autotrophic (CHBHA) system was developed to remove perchlorate under low chemical dosages and energy consumption. The perchlorate removal performance at various hydraulic retention times (HRTs) and acetate dosages was investigated. For influent containing 10 ± 0.10 mg/L perchlorate, the optimal removal efficiency by the CHBHA system was 98.96 ± 1.62 %, 92.99 ± 2.99 %, 97.85 ± 0.41 %, and 98.24 ± 1.56 % at different operating stages. Perchlorate was mainly removed in the heterotrophic part (H-part) at a sufficient HRT (6 h) and acetate dosage (14.75 mg/L). At other stages, perchlorate was synergistically removed by the H-part and electrochemical hydrogen autotrophic part (E-part). Since the H-part removed some perchlorate, the E-part's applied current decreased, thus reducing energy costs. The maximum current efficiency of CHBHA system was 22.09 %. Compared with the single E-part system, the combined system used 65 % less energy. Perchlorate was converted into active chlorine in the E-part, which improved the effluent quality. The bacterial community structures of the two parts were significantly different. Comamonas, Dechloromonas, Acinetobacter, and Chryseobacterium were enriched in the H-part, and the dominant genera in the E-part were Thauera, Azonexus, Hydrogenophaga, and Tissierella.

Effect of steel slag on ammonia removal and ammonia-oxidizing microorganisms in zeolite-based tidal flow constructed wetlands

The ammonia removal performance of tidal flow constructed wetlands (TFCWs) requires to be improved under high hydraulic loading rates (HLRs). The pH decrease caused by nitrification may adversely affect the NH₄⁺-N removal and ammonia-oxidizing microorganisms (AOMs) of TFCWs. Herein, TFCWs with zeolite (TFCW_Z) and a mixture of zeolite and steel slag (TFCW_S) were built to investigate the influence of steel slag on NH₄⁺-N removal and AOMs. Both TFCWs were operated under short flooding/drying (F/D) cycles and high HLRs (3.13 and 4.69 m³/(m² d)). The results revealed that a neutral effluent pH (6.98-7.82) was achieved in TFCW_S owing to the CaO dissolution of steel slag. The NH₄⁺-N removal efficiencies in TFCW_S (91.2 ± 5.1%) were much higher than those in TFCW_Z (73.2 ± 7.1%). Total nitrogen (TN) removal was poor in both TFCWs mainly due to the low influent COD/TN. Phosphorus removal in TFCW_S was unsatisfactory because of the short hydraulic retention time. The addition of steel slag stimulated the flourishing AOMs, including Nitrosomonas (ammonia-oxidizing bacteria, AOB), Candidatus_Nitrocosmicus (ammonia-oxidizing archaea, AOA), and comammox Nitrospira, which may be responsible for the better ammonia removal performance in TFCW_S. PICRUSt2 showed that steel slag also enriched the relative abundance of functional genes involved in nitrification (amoCAB, hao, and nxrAB) but inhibited genes related to denitrification (nirK, norB, and nosZ). Quantitative polymerase chain reaction (qPCR) revealed that complete AOB (CAOB) and AOB contributed more to the amoA genes in TFCW_S and TFCW_Z, respectively. Therefore, this study revealed that the dominant AOMs could be significantly changed in zeolite-based TFCW by adding steel slag to regulate the pH in situ, resulting in a more efficient NH₄⁺-N removal performance.

Enhancing Effects of Sludge Biochar on Aerobic Granular Sludge for Wastewater Treatment

Sludge biochar can be used as bio-carrier to enhance aerobic granular sludge, however, its impact on the formation and especially long-term stability of aerobic granules has not been fully investigated. In this paper, aerobic granular sludge was cultivated in two parallel sequencing batch reactors (SBRs), R1 and R2, with and without sludge biochar addition in the activated sludge inoculum, respectively. The sludge characteristics, wastewater treatment performance, and microbial community structure of granular sludge were examined on a 240-day operation, during which aerobic granular sludge in the two reactors experienced dynamic changes including granule formation, maturation, breakage, filamentous proliferation, and recovery. Aerobic granules in R1 with biochar formed two weeks earlier than that in R2, presenting a larger mean size, and higher settling ability and biomass retention in the granule maturation period. Concurrently, aerobic granules in R1 showed higher denitrification ability with over 80% removal efficiency throughout the whole operation period. During the maturation period, the ratio of food to biomass (F/M) in R1 was below 0.5 gCOD/gVSS d while it ranged between 0.5 and 1.0 gCOD/gVSS d in R2 due to lower biomass retention. The elemental analysis showed more Ca and P accumulation in aerobic granular sludge from R1, with 3% Ca and 2.75% P in sludge from R1 and 0.91% Ca and 0.75% P in sludge from R2, respectively. The microbial community in R1 had higher richness, diversity, excretion of extracellular polymer substances (EPSs) and abundance of denitrifying genera than that in R2, supporting its higher stability and denitrification performance. These results demonstrated that aerobic granular sludge formed by using sludge biochar as a carrier for granulation can speed up granule formation, improve denitrification performance, and enhance the long-term stability of aerobic granules. The findings disclosed the enhancing effects of biochar for wastewater treatment by aerobic granular sludge, suggesting the potential of practical application of biochar in aerobic granular sludge-based reactors.

Identification of key water parameters and microbiological compositions triggering intensive N2O emissions during landfill leachate treatment process

Landfill leachate treatment processes tend to emit more N₂O compared to domestic wastewater treatment. This discrepancy may be ascribed to leachate water characteristics such as high refractory COD, ammonium (NH₄⁺) content, and salinity. In this work, the leachate influent was varied to examine the N₂O emission scenarios. NH₄⁺-N, COD, and Cl^- concentrations ranged between 1000-2500, 1000-10,000, and 500-3000 mg L^-1, respectively. Simultaneously, we attempted to combine statistical analysis with high-throughput sequencing to understand the microbial mechanism with regards to N₂O emission. Results show that the strong N₂O emissions occur in the nitrifying tank due to the intensive aeration. The system receiving the lowest COD shows the maximum N₂O emission factor of 42.7% of the removed nitrogen. Both redundancy analysis and a structural equation model verify that insufficient degradable organics are the key water parameter triggering intensive N₂O emission within the designed influent limits. Furthermore, two essential but non-abundant functional bacteria, Flavobacterium (acting as a denitrifier) and Nitrosomonas (acting as a nitrifier), are identified as the core functional species that dramatically influence N₂O emissions. An increase in influent COD promotes the proliferation of Flavobacterium and inhibits Nitrosomonas, which in turn reduce N₂O release. Meanwhile, two keystone species of Castellaniella and Saprospiraceae unclassified are recognized. They may supply a suitable niche and integrity of the microbial community for N-cycle functional bacteria. These findings reveal the essential role of non-abundant species in microbial community, and expand the current understanding of microbial interactions underlying N₂O dynamics in leachate treatment systems.

An enhanced excess sludge fermentation process by anthraquinone-2-sulfonate as electron shuttles for the biorefinery of zero-carbon hydrogen

Excess sludge (ES) largely produced in municipal wastewater treatment plants is known as a waste biomass and the traditional treatment processes such as landfill and incineration are considered as unsustainable due to the negative environmental impact. Fermentation process of ES for the biorefinery of zero-carbon hydrogen has attracted an increasing interesting and was extensively researched in the last decades. However, the technology is far from commercial application due to the insufficient effectivity. In the present study, anthraquinone-2-sulfonate (AQS) as electron shuttles was introduced into the fermentation process of ES for mediating the composition and activity of bacterial community to get an enhanced biohydrogen production. Inoculated with the same anaerobic activated sludge of 1.12 gVSS/L, a series of batch anaerobic fermentation systems with various dosage of AQS were conducted at the same ES load of 2.75 gVSS/L, initial pH 6.5 and 35 °C. The results showed that the fermentation process was remarkably enhanced by the introduction of 100 mg/L AQS, accompanying the lag phase was shortened to 1.35 h from 7.62. The obtained biohydrogen yield and the specific biohydrogen production rate were also remarkably enhanced to 24.9 mL/gVSS and 0.3 mL/(gVSS·h), respectively. Illumina Miseq sequencing showed that Longilinea and Guggenheimella as the dominant genera had been enriched from 9.2% to 0-12.0% and 4.7%, respectively, in the presence of 100 mg/L AQS. Function predicted analysis suggested that the presence of AQS had increased the abundance of genes involved in the transport and metabolism of carbohydrate, amino acid and energy production. Further redundancy analysis (RDA) revealed that the enhanced hydrogen production was highly positively correlated with the enrichment of genera such as Longilinea and Guggenheimella. The research work presents a novel potential biorefinery of ES for the effective production of zero-carbon hydrogen.

Ottowia testudinis sp. nov., isolated from the cloaca of a giant Asian pond turtle (Heosemys grandis)

A bacterial strain designated 27CT isolated from the cloaca of a giant Asian pond turtle was subjected to polyphasic taxonomic characterization. The strain was Gram-stain negative and oxidase- and catalase-positive. It had highest 16S rRNA gene sequence similarity to Ottowia beijingensis GCS-AN-3T (97.6 %) and Ottowia flava GY511T 96.0% and less than 96.0 % to other established species including Ramlibacter rhizophilus YS3.2.7T, Ottowia konkukae SK3863T, Acidovorax caeni E-24608T and Ottowia thiooxydans DSM 14619T. Phylogenetically, strain 27CT formed a branch with O. beijingensis GCS-AN-3T within the Ottowia clade. The genome size was 4.32 Mbp and the G+C content was 65.7 mol%. Strain 27CT shared highest ANIb values with O. beijingensis GCS-AN-3T (82.71/82.73 %) followed by O. oryzae KADR8-3T (78.9/79.0 %) and O. caeni BD-1T (73.3/75.2 %). The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid and the quinone system was ubiquinone Q-8. Predominant compounds in the polar lipid profile were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylmonomethylethanolamine. Major polyamines were 2-hydroxyputrescine and putrescine. In the fatty acid profile, summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c), C16 : 0, summed feature 8 (C18 : 1  ω7c and/or C18 : 1  ω6c), C14 : 0, C10 : 0 3-OH and C16 : 0 2-OH were detected. All these data identify strain 27CT as representing a novel species of the genus Ottowia and hence we propose the name Ottowia testudinis sp. nov. The type strain is 27CT (=CCM 9138T=LMG 32213T).

Ottowia caeni sp. nov., a novel phenylacetic acid degrading bacterium isolated from sludge

A novel bacterium, designated BD-1^T, was isolated from a sludge sample. Cells of the novel Gram-stain-negative strain were identified to be facultative anaerobic, non-motile and short rod-shaped. Growth occurred at 15-37 °C (optimum, 30 °C), pH 5.0-10.0 (pH 7.0) and in 0-4.0  % NaCl (2.0 %, w/v). The 16S rRNA gene sequence of strain BD-1^T showed the highest sequence similarity to Ottowia thiooxydans DSM 14619^T (97.0 %), followed by Ottowia pentelensis DSM 21699^T (96.3 %) and less than 96 % to other related strains. The phylogenetic trees revealed that strain BD-1^T clustered within the genus Ottowia. Summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c, 48.2 %), C_16 : 0 (23.2 %) and summed feature 8 (C_18 : 1  ω7c and/or C_18 : 1  ω6c, 8.6 %) were the major fatty acids (>5 %), and ubiquinone-8 was the respiratory quinone. Phosphatidylethanolamine, phosphatidylmethylethanolamine and phosphatidylglycerol were identified as the major polar lipids. Meanwhile, the G+C content of the DNA was 63.6 mol% based on the draft genome analysis. The average nucleotide identity and digital DNA-DNA hybridization values between strain BD-1^T and DSM 14619^T were 74.5 and 21.4  %, respectively. In addition, the novel strain completely degraded 500 mg l^-1 phenylacetic acid within 72 h under the condition of 3 % NaCl. Given the results of genomic, phylogenetic, phenotypic and chemotaxonomic analyses, strain BD-1^T was considered to represent a novel species of the genus Ottowia, for which the name Ottowia caeni sp. nov. is proposed. The strain is a potential resource for the bioremediation of phenylacetic acid contaminated water. The type strain is BD-1^T (=CGMCC 1.18541^T=KCTC 82183^T).

Effects of an organic carbon source on the coupling of sulfur(thiosulfate)-driven denitration with Anammox process

The sulfur(thiosulfate)-driven autotrophic denitrification coupled with Anammox (SDDA) process is proposed as an emerging technology for wastewater containing NH₄⁺-N and NO₃^--N. However, the influence of organic matter on the SDDA process is not fully understood. A long-term experiment has shown that a moderate organic (acetate) (＜140 mg/L COD) can accelerate the heterotrophic/autotrophic denitrification and Anammox activity, to reach as high as 92.8% ± 0.3% total nitrogen at a loading rate of 1.34 kg-N/(m³·d). Batch test results showed that Anammox made the largest contribution to the removal of nitrogen, even in an SDDA system with COD addition. Additionally, organics can promote the bioavailability of solid sulfur through reaction with sulfide to form polysulfides, which increased nitrite accumulation to forward Anammox process. Sulfur-oxidizing bacteria (e.g., Thiobacillus and Denitratisoma) coexisted with Anammox bacteria (e.g., Ca. Brocadia and Ca. Kuenenia) in the SDDA system despite the addition of exogenous COD.

Comparison of an integrated short-cut biological nitrogen removal process with magnetic coagulation treating swine wastewater and food waste digestate

An integration of two processes, magnetic coagulation (MC) and short-cut biological nitrogen removal (SBNR), coupled with a sequencing batch membrane bioreactor (SMBR) controlled by an automatic real-time control strategy (RTC), was developed to treat different characteristics of high strength wastewater. The treatment efficiency and microbial community-diversity of the proposed method was evaluated and investigated using swine wastewater and food waste (FW) digestate. The MC showed high removal of TSS (89.1 ± 1.5%, 92.21 ± 1.8%), turbidity (90.58 ± 2.1%, 95.1 ± 2.1%), TP (88.5 ± 1.9%, 92.1 ± 1.5%), phosphate (87.76 ± 1.6%, 91.22 ± 1.5%), and SMBR achieved stable and excellent removal of COD (96.05 ± 0.2%, 97.39 ± 0.2%), TN (97.30 ± 0.3%, 97.44 ± 0.3%) andNH₄⁺-N (99.07 ± 0.2%, 98.54 ± 0.2%) for swine wastewater and FW digestate, respectively. The effluent COD andNH₄⁺-N concentrations were found to meet their discharge standards. The microbial community comparison showed similar diversity and richness, and genus Diaphorobacter and Thaurea were dominant in denitritation, and Nitrosomonas was dominant in nitritation treating both swine wastewater and FW digestate.

Hydrogenophaga aromaticivorans sp. nov., isolated from a para-xylene-degrading enrichment culture, capable of degrading benzene, meta- and para-xylene

A benzene, para- and meta-xylene-degrading Gram-stain-negative, aerobic, yellow-pigmented bacterium, designated as D2P1^T, was isolated from a para-xylene-degrading enrichment culture. Phylogenetic analyses based on 16S rRNA genes showed that D2P1^T shares a distinct phyletic lineage within the genus Hydrogenophaga and shows highest 16S rRNA gene sequence similarity to Hydrogenophaga taeniospiralis NBRC 102512^T (99.2 %) and Hydrogenophaga palleronii NBRC 102513^T (98.3 %). The draft genome sequence of D2P1^T is 5.63 Mb long and the genomic DNA G+C content is 65.5 %. Orthologous average nucleotide identity (OrthoANI) and digital DNA-DNA hybridization (dDDH) analyses confirmed low genomic relatedness to its closest relatives (OrthoANI <86 %; dDDH <30 %). D2P1^T contains ubiquinone 8 (Q-8) as the only respiratory quinone and phospholipid, phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol as major polar lipids. The main whole-cell fatty acids of D2P1^T are summed feature 3 (C_16 : 1  ω7c/C_16 : 1  ω6c), C_16 : 0 and summed feature 8 (C_18 : 1  ω7c/C_18 : 1  ω6c). The polyphasic taxonomic results indicated that strain D2P1^T represents a novel species of the genus Hydrogenophaga, for which the name Hydrogenophaga aromaticivorans sp. nov. is proposed. The type strain is D2P1^T (=LMG 31780^T=NCAIM B 02655^T).

Effective pretreatment of lignocellulosic co-substrates using barley straw-adapted microbial consortia to enhanced biomethanation by anaerobic digestion

Microbial pretreatments have been identified as a compatible and sustainable process with anaerobic digestion compared to energy-intensive physicochemical pretreatments. In this study, barley straw and hay co-substrate was pretreated with a microaerobic barley straw-adapted microbial (BSAM) consortium prior to anaerobic digestion. The improved digestibility was investigated through 16S rRNA gene sequencing, microbial counts and C:N ratios. BSAM pretreatment resulted in 15.2 L kg^-1 TS of methane yield after 35 days, almost 40 times more than the control. The methane content in total biogas produced were 58% (v/v) and 10% (v/v) in BSAM and control, respectively. This research demonstrated that BSAM-based pretreatment significantly increased the digestibility and surface area of the lignocellulosic material and considerably enhanced biomethanation. This study generates new potential bio-research opportunities in the emerging field of lignocellulosic anaerobic digestion-biorefineries.

Exploring the optimized strategy in the nitritation-anammox biofilm process for treating low ammonium wastewater

The main challenge for achieving the simultaneous nitritation, anammox and denitrification (SNAD) process is to optimize the concentrations of nitrite and dissolved oxygen (DO). This study explored the performance of SNAD biofilm reactor under three operational strategies. At Stage 1, 2 and 3, the average concentrations of DO were 0.7, 2.7 and 5.2 mg/L, respectively. The peak concentrations of NO₂^--N in the sequencing batch reactor (SBR) cycle were 5.3, 6.0 and 2.7 mg/L, respectively. The average removal rates of total inorganic nitrogen (TIN) were 0.30, 0.42 and 0.22 kg N/m³/d, respectively. Protein (PN) was the dominant extracellular polymeric substance (EPS) content on the SNAD biofilm. The PN concentration remained stable while the polysaccharide (PS) concentration changed rapidly under different operational strategies. High-throughput sequencing analysis indicated that high DO and long aeration period condition could lead to a slight decrease in the abundances of denitrifying bacteria and anammox bacteria.

Effect of influent ammonia nitrogen concentration on microbial community in MBBR reactor

The purpose of this study is to explore the nitrogen removal efficiency of the moving bed biofilm reactor (MBBR) under different ammonia nitrogen concentrations (states P1-P5), especially the composition of various forms of nitrogen, related genes and microbial community structure and succession law in the effluent of the reactor. The results show that the average efficiency of MBBR effluent denitrification is 63.63%. The concentration dynamics of NO₃^--N and NO₂^--N in the effluent indicated a relatively short-range nitrification and denitrification reaction in the MBBR. The results of 16SrDNA sequencing of P1-P5 microbial samples found that changes in the concentration of ammonia nitrogen in the influent produced significant changes in the composition of the microbial community in the MBBR. The genera Ottowia and Flavobacterium played an important role in the nitrogen removal of the MBBR system.

Hydrolase activity and microbial community dynamic shift related to the lack in multivalent cations during cation exchange resin-enhanced anaerobic fermentation of waste activated sludge

The correlation of the lack in multivalent cations with hydrolase activity and microbial community in anaerobic fermentation of waste activated sludge was investigated in this study. It was demonstrated that considerable solid phase reduction of 41 % (7.87 g/L) was achievable through a cation exchange resin-enhanced anaerobic fermentation of 4 days. The protease and α-glucosidase, especially α-glucosidase, were easily influenced by a lack in multivalent cations. Furthermore, species abundance and diversity of microbial community gradually decreased. Meanwhile, the bacteria community structure presented obvious dynamic shifts. Ruminococcaceae_UCG_009, Bacteroides and Macellibacteroides responsible for organic matter biodegradation and SCFAs production became dominant bacteria in cation exchange resin-enhanced anaerobic fermentation, which was less influenced by the lack in multivalent cations, while the SCFA consumers (e.g. methanogens) were inhibited with reduced abundances due to their susceptibility to the lack in multivalent cations. Redundancy analysis revealed that the lack in multivalent cations were responsible for the microbial community evolution, which was proved by the high Grey relational coefficients (0.747-0.820) and significant negative Spearman coefficients (-0.5798 to -0.9429) between multivalent cation and microbial community. Obviously, the cation exchange resin-induced removal of multivalent cations reduced enzyme activity and modified microbial community structure, which created a beneficial environment for enhancing anaerobic fermentation.

Identification and characterization of the proteolytic flagellin from the common freshwater bacterium Hylemonella gracilis

Flagellins are the protein components of bacterial flagella and assemble in up to 20,000 copies to form extracellular flagellar filaments. An unusual family of flagellins was recently discovered that contains a unique metalloprotease domain within its surface-exposed hypervariable region. To date, these proteolytic flagellins (also termed flagellinolysins) have only been characterized in the Gram-positive organism Clostridium haemolyticum, where flagellinolysin was shown to be proteolytically active and capable of cleaving extracellular protein substrates. The biological function of flagellinolysin and its activity in other organisms, however, remain unclear. Here, using molecular biochemistry and proteomics, we have performed an initial characterization of a novel flagellinolysin identified from Hylemonella gracilis, a Gram-negative organism originally isolated from pond water. We demonstrate that H. gracilis flagellinolysin (HgrFlaMP) is an active calcium-dependent zinc metallopeptidase and characterize its cleavage specificity profile using both trypsin and GluC-derived peptide libraries and protein substrates. Based on high-throughput degradomic assays, HgrFlaMP cleaved 784 unique peptides and displayed a cleavage site specificity similar to flagellinolysin from C. haemolyticum. Additionally, by using a set of six protein substrates, we identified 206 protein-embedded cleavage sites, further refining the substrate preference of HgrFlaMP, which is dominated by large hydrophobic amino acids in P1', and small hydrophobic or medium-sized polar residues on the amino-terminal side of the scissile bond. Intriguingly, recombinant HgrFlaMP was also capable of cleaving full-length flagellins from another species, suggesting its potential involvement in interbacterial interactions. Our study reports the first experimentally characterized proteolytic flagellin in a Gram-negative organism, and provides new insights into flagellum-mediated enzymatic activity.

Insights into electroactive biofilms for enhanced phenolic degradation of coal pyrolysis wastewater (CPW) by magnetic activated coke (MAC): Metagenomic analysis in attached biofilm and suspended sludge

To investigate the role of electroactive biofilms for enhanced phenolic degradation, lignite activated coke (LAC) and MAC were used as carriers in moving-bed biofilm reactor (MBBR) for CPW treatment. In contrast to activated sludge (AS) reactor, the carriers improved degradation performance of MBBR. Although two MBBRs exerted similar degradation capacity with over 92% of COD and 93% phenols removal under the highest phenolics concentration (500 mg/L), the effluent of MAC-based MBBR remained higher biodegradability (BOD₅/COD = 0.34 vs 0.18) than that of LAC-based MBBR. Metagenomic analysis revealed that electroactive biofilms determined phenolic degradation of MAC-based MBBR. Primarily, Geobacter (17.33%) started Fe redox cycle on biofilms and developed syntrophy with Syntrophorhabdus (6.47%), which fermented phenols into easily biodegradable substrates. Subsequently, Ignavibacterium (3.38% to 2.52%) and Acidovorax (0.46% to 8.83%) conducted biological electricity from electroactive biofilms to suspended sludge. They synergized with dominated genus in suspended sludge, Alicycliphilus (19.56%) that accounted for phenolic oxidation and nitrate reduction. Consequently, the significantly advantage of Geobater and Syntrophorhabdus was the keystone reason for superior biodegradability maintenance of MAC-based MBBR.

Lack of Evidence for Microbiota in the Placental and Fetal Tissues of Rhesus Macaques

The prevailing paradigm in obstetrics has been the sterile womb hypothesis. However, some are asserting that the placenta, intra-amniotic environment, and fetus harbor microbial communities. The objective of this study was to determine whether the fetal and placental tissues of rhesus macaques harbor bacterial communities. Fetal, placental, and uterine wall samples were obtained from cesarean deliveries without labor (∼130/166 days gestation). The presence of bacteria in the fetal intestine and placenta was investigated through culture. The bacterial burden and profiles of the placenta, umbilical cord, and fetal brain, heart, liver, and colon were determined through quantitative real-time PCR and DNA sequencing. These data were compared with those of the uterine wall as well as to negative and positive technical controls. Bacterial cultures of fetal and placental tissues yielded only a single colony of Cutibacterium acnes This bacterium was detected at a low relative abundance (0.02%) in the 16S rRNA gene profile of the villous tree sample from which it was cultured, yet it was also identified in 12/29 background technical controls. The bacterial burden and profiles of fetal and placental tissues did not exceed or differ from those of background technical controls. By contrast, the bacterial burden and profiles of positive controls exceeded and differed from those of background controls. Among the macaque samples, distinct microbial signals were limited to the uterine wall. Therefore, using multiple modes of microbiologic inquiry, there was not consistent evidence of bacterial communities in the fetal and placental tissues of rhesus macaques.IMPORTANCE Microbial invasion of the amniotic cavity (i.e., intra-amniotic infection) has been causally linked to pregnancy complications, especially preterm birth. Therefore, if the placenta and the fetus are typically populated by low-biomass microbial communities, current understanding of the role of microbes in reproduction and pregnancy outcomes will need to be fundamentally reconsidered. Could these communities be of benefit by competitively excluding potential pathogens or priming the fetal immune system for the microbial bombardment it will experience upon delivery? If so, what properties (e.g., microbial load and community membership) of these microbial communities preclude versus promote intra-amniotic infection? Given the ramifications of the in utero colonization hypothesis, critical evaluation is required. In this study, using multiple modes of microbiologic inquiry (i.e., culture, quantitative real-time PCR [qPCR], and DNA sequencing) and controlling for potential background DNA contamination, we did not find consistent evidence for microbial communities in the placental and fetal tissues of rhesus macaques.

Integrated leachate management approach incorporating nutrient recovery and removal

This manuscript presents an integrated management scheme for leachate which employed struvite precipitation to recover ammonia nitrogen and phosphorus, aerobic granular sludge process for carbon oxidation (in the form of BOD and sCOD) and single stage anaerobic ammonia oxidation (ANAMMOX) for nitrogen management. The influent fed to the integrated treatment scheme was a mixture of anaerobic digester centrate and real leachate in 4:1 ratio. Almost 77% recovery of phosphorus and 25% removal of NH₄⁺-N were accomplished through struvite precipitation at an optimum pH of 9. High pH contributed to free ammonia loss during struvite precipitation experiments. In the aerobic granular sludge reactor overall, BOD₅, COD and NH₄⁺-N removal percentages were 74%, 45% and 35% and in the PN/A reactor, overall 35% removal of total inorganic nitrogen (TIN) was observed. More than 80% BOD removal was recorded in the granular reactor with soluble COD (sCOD) removal fluctuating between 28 and 57% depending on the operational phase. High-throughput amplicon sequencing of 16S rRNA gene targeting V4 region revealed a dominance of phylum Planctomycetes, in the PN/A reactor system. Presence of Rhodobacteraceae, Xanthomonadaceae, Flavobacteriaceae in the granular biomass confirmed the defined redox zones inside mature granules indicating simultaneous removal of nitrogen (N) and organics in aerobic granular sludge technology. Exposing the synthetically cultured aerobic granules directly to the mixture of leachate and centrate unveiled an alteration in physical characteristics of granules; however, reactor operational data and microbial community analysis ascertain the effectiveness of the treatment scheme treating two urban waste-streams.

Nitrogen removal from food waste digestate using partial nitritation-anammox process: Effect of different aeration strategies on performance and microbial community dynamics

The feasibility of employing anammox and partial nitritation-anammox (PN/A) processes for nitrogen removal from food waste (FW) digestate was investigated in this study. The effects of different aeration strategies on the microbial community were also investigated. To achieve this, after anammox enrichment (Phase 1), the reactor was fed with digestate supplemented with nitrite (Phase 2), and subsequently different aeration strategies were evaluated to establish PN/A. Aeration strategies with high anoxic periods (30 and 45 min) in relation to aerobic periods (15 min) coupled with low air flow rates (0.026 L  min^-1. L_reator^-1) were found to be better for establishing PN/A, as coefficients of produced nitrate/removed ammonium were closer to those reported previously (0.17 and 0.21). Aeration conditions considerably altered the microbial community. Candidatus Brocadia was replaced by Candidatus Jettenia, after the first aeration strategies. These results support the feasibility of FW digestate treatment using anammox and PN/A processes and provide a better understanding of the effect of aeration on microbial dynamics in PN/A reactors.

Coupling of sulfur(thiosulfate)-driven denitratation and anammox process to treat nitrate and ammonium contained wastewater

This study investigated the feasibility of a new biological nitrogen removal process that integrates sulfur-driven autotrophic denitratation (NO₃^-→NO₂^-) and anaerobic ammonium oxidation (Anammox) for simultaneous removal of nitrate and ammonium from industrial wastewater. The proposed sulfur(thiosulfate)-driven denitratation and Anammox process was developed in two phases: First, the thiosulfate-driven denitratation was established in the UASB inoculated with activated sludge and fed with ammonium, nitrate and thiosulfate for 52 days until the nitrite level in the effluent reached 32.1 mg N/L. Second, enriched Anammox biomass was introduced to the UASB to develop the integrated thiosulfate-driven denitratation and Anammox (TDDA) bioprocess (53-212 d). Results showed that nitrate and ammonium could be efficiently removed from synthetic wastewater by the integrated TDDA system at a total nitrogen (TN) removal efficiency of 82.5 ± 1.8% with an influent NH₄⁺-N of 101.2 ± 2.2 mgN/L, NO₃^--N of 101.1 ± 1.5 mgN/L and thiosulfate of 202.5 ± 3.2 mg S/L. It was estimated that Anammox and autotrophic denitritation (NO₂^-→N₂) contributed to about 90% and 10% of the TN removal respectively at stable operation. The established TDDA system was further supported by high-throughput sequencing analysis that sulfur-oxidizing bacteria (e.g., Thiobacillus and Sulfurimonas) coexisted with Anammox bacteria (e.g., Ca. Kuenenia and Ca. Anammoxoglobus) in this syntrophic biocenosis. Additionally, batch experiments were conducted to reveal the kinetic rates and to reconcile the stoichiometry of the electron donor/acceptor couples of the TDDA process. The results unraveled the mechanisms in the new bioprocess: i) sulfite and elemental sulfur (S⁰) were initially generated from branched thiosulfate; ii) oxidation of sulfite and elemental sulfur coupled with fast and slow denitratation; iii) nitrite produced from denitratation together with ammonium were effectively converted to dinitrogen gas via Anammox.

Enhanced nitrogen removal of the simultaneous partial nitrification, anammox and denitrification (SNAD) biofilm reactor for treating mainstream wastewater under low dissolved oxygen (DO) concentration

The simultaneous partial nitrification, anammox and denitrification (SNAD) process for treating mainstream wastewater was investigated under different intermittent aeration modes. By controlling the aeration time of 20, 60 and 180 min during the intermittent modes, the oxygen concentration remained 3.50, 1.45 and 0.70 mg·L^-1. Correspondingly, the reactor achieved the nitrogen removal rate of 0.17, 0.29 and 0.30 kg N·m^-3·d^-1. Meanwhile, the average total inorganic nitrogen (TIN) removal efficiency reached 93.4%, 87.5% and 92.7%. The effluent NO₃^--N concentration was very low. High-throughput sequencing analysis indicated that the proportion of nitrite oxidization bacteria (NOB), anammox bacteria and denitrification bacteria was 0.15%, 0.33% and 8.78%. Candidatus Anammoxoglobus was the abundant anammox bacteria genus. Further study on the unclassified sequences revealed the possibility of the high relative abundance of Nitrosomonas-related genus and Candidatus Kuenenia-related genus on the SNAD biofilm.

Ottowia flava sp. nov., isolated from fish intestines

A novel Gram-negative bacterium, non-motile and short rod-shaped, designated strain GY511^T, was isolated from the intestines of fish collected from Maowei Sea, China. Growth occurred at pH 6.0-9.0 (optimum 7.0), 4-37 °C (optimum 28 °C) and at 0-2.5% (w/v) NaCl (optimum 1.0%). The result of 16S rRNA gene sequence analysis showed that strain GY511^T is closely related to O. oryzae NBRC 113109^T (97.6%), O. konkukae DSM 105395^T (97.4%), Ottowia beijingensis CGMCC 1.12324^T (95.9%), Ottowia pentelensis DSM 21699^T (95.2%) and Ottowia thiooxydans DSM 14619^T (95.0%). The DNA-DNA hybridization values of strain GY511^T with O. oryzae NBRC 113109^T and O. konkukae DSM 105395^T were 35.4 ± 3.1% and 26.3 ± 1.8%, respectively. The major fatty acids (> 10%) were identified as summed feature 3 (C_16:1ω7c and/or C_16:1ω6c), C_16:0 and summed feature 8 (C_18:1ω7c and/or C_18:1ω6c) and the major respiratory quinone was ubiquinone-8 (Q-8). The polar lipids comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylmethylethanolamine, two unidentified aminolipids and an unidentified phospholipid. The G+C content of the genomic DNA was 62.9 mol%. Thiosulfate could be utilized as co-substrate for aerobic growth and was oxidised to sulfate. On the basis of phenotypic, chemotaxonomic and molecular data, strain GY511^T is considered to represent a novel species of the genus Ottowia, for which the name Ottowia flava sp. nov. is proposed. The type strain is GY511^T (= NBRC 113500^T = DSM 107425^T = CGMCC 1.13650^T).

Operation mode of a step-feed anoxic/oxic process with distribution of carbon source from anaerobic zone on nutrient removal and microbial properties

This study investigated the operation mode of a step-feed anoxic/oxic (A/O) process with distribution of the carbon source from the anaerobic zone in terms of the treatment effects on sewage with low carbon and high nitrogen and phosphorus. After seven phases of operation, an optimal flow distribution ratio of 75%:25% was obtained from the anaerobic zone, and the concentrations of chemical oxygen demand, ammonia nitrogen, total nitrogen, and total phosphorous in the effluent were 20.8, 0.64, 14.2, and 0.89 mg/L, respectively. The presence of an internal reflux system in the deaeration zone improved the treatment. 16S rRNA high-throughput sequencing revealed that the microbial communities in aerobic zone I(O1) of the first-step A/O sludge were different from those in aerobic zone I (O2) of the second-step A/O sludge, whereas microbial communities of the seed sludge were similar to those in O2 of the second-step A/O sludge. The richness and diversity of microbial communities in O1 of the first-step A/O sludge samples were higher than those in O2 of the second-step A/O and seed sludge. At the optimal flow distribution ratio, the microbial abundance and treatment removal efficiency were the highest.

Effect of temperature on nitrogen removal and biological mechanism in an up-flow microaerobic sludge reactor treating wastewater rich in ammonium and lack in carbon source

Previous study has demonstrated that microaerobic process is effective in nitrogen removal from the wastewater with high ammonium and low carbon to nitrogen ratio. In the microaerobic system, synergistic action of anammox, ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB) and denitrifiers was the key issues to remove nitrogen from the wastewater rich in ammonium. Temperature has a significant effect on specific growth rate and activity of various nitrogen removal functional bacteria. In this study, the effect of temperature (35 °C-15 °C) on nitrogen removal were investigated in an up-flow microaerobic sludge reactor (UMSR) at the HRT of 8 h and reflux ratio of 45. Above 71.2% of total nitrogen (TN) and 80.7% of NH₄⁺ removal efficiencies were observed at the temperature no less than 17 °C. With the temperature further decreasing to 15 °C, denitrifiers still dominant the UMSR, but AOB, NOB and Candidatus Brocadia as the predominant anammox bacteria were inhibited revealed by high throughput sequencing, resulting in the decrease of TN and NH₄⁺ removal to 39.7% and 61.8%, respectively. Fortunately, when the temperature rebounded to 20 °C, a higher TN and NH₄⁺ removal of 81.2% and 97.3% were obtained again in the UMSR.

Assessing the performance of a sequencing batch biofilm reactor bioaugmented with P. stutzeri strain XL-2 treating ammonium-rich wastewater

Pseudomonas stutzeri XL-2, with the capability of heterotrophic nitrification-aerobic denitrification and biofilm-forming, was applied in a sequencing batch biofilm reactor (SBBR) for bioaugmented treatment of ammonium-rich wastewater. The bioaugmented system SBBR 1 showed a rapid development of biofilm and relatively shorter time for biofilm hanging compared with the control system SBBR 2 without strain XL-2 inoculation. At different NH₄⁺-N loads of 100, 200 and 300 mg/L, the effluent TN removal ratios ranged in 88.7-97.0%, 85.1-93.5% and 87.8-92.5% respectively in SBBR 1, while only ranged in 77.4-85.4%, 77.1-84.3% and 79.8-85.0% in SBBR 2. Less accumulation of NO₂^--N and NO₃^--N resulted in the better performance on TN removal in SBBR 1. Microbial community structure analysis revealed that strain XL-2 successfully proliferated in SBBR 1 and contributed to the less accumulation of NO₂^--N and NO₃^--N as well as biofilm formation.

Ottowia konkukae sp. nov., isolated from rotten biji (tofu residue)

A Gram-negative, aerobic, non-motile, non-spore-forming and rod-shaped bacterial strain, designated SK3863^T, was isolated from rotten biji (residue remaining after making tofu). This bacterium was characterized in order to determine its taxonomic position by using the polyphasic approach. Strain SK3863^T grew well at 25-37 °C on Reasoner's 2A agar plates. On the basis of 16S rRNA gene sequence similarity, strain SK3863^T belonged to the family Comamonadaceae and was related to Ottowia beijingensis GCS-AN-3^T (96.5 % sequence similarity) and Ottowia pentelensis RB3-7^T (96.4 %). Lower sequence similarities (96.2 %) were found to all of the other recognized members of the genus Ottowia. The G+C content of the genomic DNA was 65.8 mol%. The major respiratory lipoquinone was ubiquinone 8 and the major fatty acids were C16 : 1ω6c/C16 : 1ω7c, C16 : 0 and C18 : 1ω7c/C18 : 1ω6c. Strain SK3863^T could be differentiated genotypically and phenotypically from the recognized species of the genus Ottowia. The isolate therefore represents a novel species, for which the name Ottowia konkukae sp. nov. is proposed, with the type strain SK3863^T (=KCCM 43236^T=DSM 105395^T).

Ottowia oryzae sp. nov., isolated from Andong sikhye, a Korean traditional rice beverage

A Gram-stain-negative, non-spore-forming, non-motile, short-rod-shaped bacterial strain, designated KADR8-3^T, isolated from Andong sikhye in Andong-si, Gyeongsangbuk-do, Republic of Korea, was characterized using a polyphasic approach. On the basis of morphological, genetic and chemotaxonomic characteristics, it was determined to belong to the genus Ottowia. The phylogenetic similarity based on the 16S rRNA gene sequences indicated the strain formed a clade with Ottowia beijingensis GCS-AN-3^T, Ottowia thiooxydans DSM 14619^T, Ottowia pentelensis RB3-7^T and 'Ottowia shaoguanensis' J5-66^T, showing the highest similarity to O. beijingensis GCS-AN-3^T (96.3 %). The major fatty acids were C16 : 0, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c). The predominant respiratory quinone was Q-8. The polar lipids present were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, two unidentified aminolipids and two unidentified lipids. The genomic DNA G+C content was 66.80 mol%. These results supported that strain KADR8-3^T was clearly distinguishable from its closely related species and represents a novel species of the genus Ottowia, for which the name Ottowia oryzae is proposed. The type strain is KADR8-3^T (=KACC 19325^T=NBRC 113109^T).

Effect of ciprofloxacin on biological nitrogen and phosphorus removal from wastewater

In this work, both short-term and long-term experiments were therefore conducted to assess the effects of ciprofloxacin (0.2 and 2mg·L^-1) on wastewater nutrient removal. The results showed that both levels of ciprofloxacin had no acute and chronic adverse effects on the surface integrity and viability of activated sludge. Short-term exposure to all the ciprofloxacin levels induced negligible influences on wastewater nutrient removal. However, the prolonged exposure to ciprofloxacin decreased total phosphorus and nitrogen removal efficiencies from 96.8, 95.8% (control) to 91.7, 84.9% (0.2mg·L^-1) and 90.5%, 80.2% (2mg·L^-1), respectively. The mechanism study showed that ciprofloxacin exposure suppressed denitrification and phosphorus uptake processes. It was also found that ciprofloxacin affected the transformations of intracellular polyhydroxyalkanoates and glycogen in the oxic and anoxic stages. Moreover the activities of nitrite reductase and polyphosphate kinase were inhibited by the presence of ciprofloxacin. Further analysis with high-throughput sequencing revealed that compared with the control, the abundances of polyphosphate accumulating organisms, glycogen accumulating organisms and denitrifying bacteria in ciprofloxacin exposure reactors reduced, which were consistent with the decreased nutrient removal performance measured in these reactors.

Sludge reduction and microbial community structure in an anaerobic/anoxic/oxic process coupled with potassium ferrate disintegration

An anaerobic/anoxic/oxic (AAO) wastewater treatment system combining with a potassium ferrate (K₂FeO₄) oxidation side-stream reactor (SSR) was proposed for sludge reduction. Batch experiments showed that optimal K₂FeO₄ dosage and reaction time for sludge disintegration was 100mg/g suspended solids (SS) and 24h, respectively. Subsequently, an AAO-SSR and a conventional AAO were operated in parallel to investigate effects of K₂FeO₄ oxidation on process performance, sludge characteristics and microbial community structures. The AAO-SSR process operated under the optimized condition achieved efficient COD and NH₄⁺-N removal, and reduced sludge by 47.5% with observed yield coefficient of 0.21gSS/g COD. K₂FeO₄ addition broke sludge particles, increased dissolved organic matters in the mixed liquor, and improved sludge dewaterability. Illumina-MiSeq sequencing results showed that K₂FeO₄ oxidation in the AAO-SSR decreased microbial richness and diversity, enriched slow growers (Dechloromonas), anaerobic fermentative bacteria (Azospira) and Fe(III)-reducing bacteria (Ferribacterium), but limited the growth of phosphate-accumulating organisms.

Draft Genome Sequence of Xenophilus sp., a Novel Bacterium Isolated from the Skin of a Southern Leopard Frog (Rana sphenocephala) in Florida, USA

We report here the draft genome sequence of a novel Xenophilus species cultured from the skin of a southern leopard frog (Rana sphenocephala). Compared to previously sequenced bacterial genomes, our novel isolate showed the most significant homology with Xenophilus azovorans. The assembled genome is 3,978,285 bp, with 3,704 predicted genes and one predicted plasmid.

Tibeticola sediminis gen. nov., sp. nov., a thermophilic bacterium isolated from a hot spring

Two closely related thermophilic bacterial strains, designated YIM 73013T and YIM 73008, were isolated from a sediment sample collected from a hot spring in Tibet, western Tibet province, China. The taxonomic positions of the two isolates were investigated using a polyphasic approach. The novel isolates were Gram-stain-negative, aerobic, short-rod-shaped and motile by means of a polar flagellum. They were oxidase- and catalase-positive and were able to grow at 30-55 °C (optimum, 37-45 °C), at pH 6.0-8.0 (optimum, pH 7.0) and with NaCl tolerance up to 1 % (w/v). Phylogenetic analyses based on 16S rRNA gene sequences showed that strains YIM 73013T and YIM 73008 formed a distinct lineage with respect to closely related genera in the family Comamonadaceae and shared highest 16S rRNA gene sequences similarities with Acidovorax caeni R-24608T (96.3 and 96.4 %, respectively). The respiratory quinone was ubiquinone-8 (Q-8) and the major cellular fatty acids observed were C17 : 1ω6c, C16 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The genomic DNA G+C contents of strains YIM 73013T and YIM 73008 were 68.7 and 68.3 mol%, respectively. Based on the morphological, phylogenetic and chemotaxonomic results, the two isolates represent a novel species in a new genus, for which the name Tibeticola sediminis gen. nov., sp. nov. is proposed. The type strain of Tibeticola sediminis is YIM 73013T (=DSM 101684T=KCTC 42873T).

Reducing N2O Emission from a Domestic-Strength Nitrifying Culture by Free Nitrous Acid-Based Sludge Treatment

An increase of nitrite in the domestic-strength range is generally recognized to stimulate nitrous oxide (N2O) production by ammonia-oxidizing bacteria (AOB). It was found in this study, however, that N2O emission from a mainstream nitritation system (cyclic nitrite = 25-45 mg of N/L) that was established by free nitrous acid (FNA)-based sludge treatment was not higher but much lower than that from the initial nitrifying system with full conversion of NH4(+)-N to NO3(-)-N. Under dissolved oxygen (DO) levels of 2.5-3.0 mg/L, N2O emission from the nitritation stage was 76% lower than that from the initial stage. Even when the DO level was reduced to 0.3-0.8 mg/L, N2O emission from the nitritation stage was still 40% lower. An investigation of the mechanism showed that FNA treatment caused a shift of the stimulation threshold of nitrite on N2O emission. At the nitritation stage, the maximal N2O emission factor occurred at ∼16 mg of N/(L of nitrite). However, it increased with increasing nitrite in the range of 0-56 mg of N/L at the initial stage. FNA treatment decreased the biomass-specific N2O production rate, suggesting that the enzymes relevant to nitrifier denitrification were inhibited. Microbial analysis revealed that FNA treatment decreased the microbial community diversity but increased the abundances of AOB and denitrifiers.

Enhanced bioelectrochemical reduction of p-nitrophenols in the cathode of self-driven microbial fuel cells

Reduction from PNP to PAP was enhanced by diverse bacteria on the cathode, with no energy input to the system.

Corticibacter populi gen. nov., sp. nov., a new member of the family Comamonadaceae, from the bark of Populus euramericana

Three novel endophytic strains, designated 17B10-2-12T, 26C10-4-4 and D13-10-4-9, were isolated from the bark of Populus euramericana in Heze, Shandong Province, China. They were Gram-reaction-negative, aerobic, non-motile, short-rod-shaped, oxidase-positive and catalase-negative. A phylogenetic analysis of the 16S rRNA gene showed that the three novel strains clustered with members of the family Comamonadaceae and formed a distinct branch. The isolates shared 100 % similarities among themselves and had the highest sequence similarity with Xenophilus azovorans DSM 13620T (95.2 %) and Xenophilus arseniciresistens YW8T (95.0 %), and less than 95.0 % sequence similarities with members of other species. Their major fatty acids were C16 : 0, C17 : 0 cyclo, C18 : 1ω7c and C16 : 1ω7c/C16 : 1ω6c. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and three unknown aminophospholipids. The predominant quinone was ubiquinone-8 (Q-8). The DNA G+C content was 69.5–70.0 mol%. Based on data from a polyphasic taxonomy study, the three strains represent a novel species of a novel genus of the family Comamonadaceae, for which the name Corticibacter populi gen. nov., sp. nov. is proposed. The type strain is 17B10-2-12T ( = CFCC 12099T = KCTC 42091T).

Two-step nitrification in a pure moving bed biofilm reactor-membrane bioreactor for wastewater treatment: nitrifying and denitrifying microbial populations and kinetic modeling

The moving bed biofilm reactor-membrane bioreactor (MBBR-MBR) is a novel solution to conventional activated sludge processes and membrane bioreactors. In this study, a pure MBBR-MBR was studied. The pure MBBR-MBR mainly had attached biomass. The bioreactor operated with a hydraulic retention time (HRT) of 9.5 h. The kinetic parameters for heterotrophic and autotrophic biomasses, mainly nitrite-oxidizing bacteria (NOB), were evaluated. The analysis of the bacterial community structure of the ammonium-oxidizing bacteria (AOB), NOB, and denitrifying bacteria (DeNB) from the pure MBBR-MBR was carried out by means of pyrosequencing to detect and quantify the contribution of the nitrifying and denitrifying bacteria in the total bacterial community. The relative abundance of AOB, NOB, and DeNB were 5, 1, and 3%, respectively, in the mixed liquor suspended solids (MLSS), and these percentages were 18, 5, and 2%, respectively, in the biofilm density (BD) attached to carriers. The pure MBBR-MBR had a high efficiency of total nitrogen (TN) removal of 71.81±16.04%, which could reside in the different bacterial assemblages in the fixed biofilm on the carriers. In this regard, the kinetic parameters for autotrophic biomass had values of YA=2.3465 mg O2 mg N(-1), μm, A=0.7169 h(-1), and KNH=2.0748 mg NL(-1).