Microbial communities in activated sludge performing enhanced biological phosphorus removal in a sequencing batch reactor

Research advances of the phosphorus-accumulating organisms of Candidatus Accumulibacter, Dechloromonas and Tetrasphaera: Metabolic mechanisms, applications and influencing factors

Phosphorus-accumulating organisms (PAOs), which harbor metabolic mechanisms for phosphorus removal, are widely applied in wastewater treatment. Recently, novel PAOs and phosphorus removal metabolic pathways have been identified and studied. Specifically, Dechloromonas and Tetrasphaera can remove phosphorus via the denitrifying phosphorus removal and fermentation phosphorus removal pathways, respectively. As the main PAOs in biological phosphorus removal systems, the conventional PAO Candidatus Accumulibacter and the novel PAOs Dechloromonas and Tetrasphaera are thoroughly discussed in this paper, with a specific focus on their phosphorus removal metabolic mechanisms, process applications, community abundance and influencing factors. Dechloromonas can achieve simultaneous nitrogen and phosphorus removal in an anoxic environment through the denitrifying phosphorus removal metabolic pathway, which can further reduce carbon source requirements and aeration energy consumption. The metabolic pathways of Tetrasphaera are diverse, with phosphorus removal occurring in conjunction with macromolecular organics degradation through anaerobic fermentation. A collaborative oxic phosphorus removal pathway between Tetrasphaera and Ca. Accumulibacter, or a collaborative anoxic denitrifying phosphorus removal pathway between Tetrasphaera and Dechloromonas are future development directions for biological phosphorus removal technologies, which can further reduce carbon source and energy consumption while achieving enhanced phosphorus removal.

Phosphate solubilizing epilithic and endolithic bacteria isolated from clastic sedimentary rocks, Murree lower Himalaya, Pakistan

Rock microbes are capable to solubilize phosphate present in the rocks.. In this study, we focused on the isolation of phosphate solubilizing bacteria from rocks of Murree, Pakistan. Both endolithic and epilithic bacteria were screened for phosphate solubilization. Three bacterial strains were selected based on halozone formation inNational Botanical Research Institute for phosphate) medium supplemented with TCP (tribasic calcium phosphate). The solubilization index for these bacteria was recorded as 4.29, 4.03 and 3.99. The pH of the medium dropped from 7.0 to 4.0 after 5 days with continuous shaking at 150 rpm, which facilitate the phosphate solubilization. The strains P26, P4 and N27 were identified as Pseudomonas putida strain (KT004381), Pseudomonas grimontii (KT223621) and Alcaligenes faecalis (KT004385). Strain P26 showed maximum phosphate solubilization (367.54 µg/ml), while P4 and N27 showed 321.88 and 291.36 µg/ml after 3 days of incubation. Such inorganic phosphate solubilization could be attributed to the organic acids production by bacteria. The presence of organic acids is determined by high-performance liquid chromatography. Three different types of acids, gluconic, oxalic and malic acid were the dominant acids found in the culture medium. It may be assumed that these bacteria can play a role in weathering of rocks as well. PSB is likely to serve as an efficient biofertilizer, especially in areas deficient in P to increase the overall performance of crops.

Linear Six-Carbon Sugar Alcohols Induce Lysis of Microcystis aeruginosa NIES-298 Cells

Cyanobacterial blooms are a global concern due to their adverse effects on water quality and human health. Therefore, we examined the effects of various compounds on Microcystis aeruginosa growth. We found that Microcystis aeruginosa NIES-298 cells were lysed rapidly by linear six-carbon sugar alcohols including mannitol, galactitol, iditol, fucitol, and sorbitol, but not by other sugar alcohols. Microscopic observations revealed that mannitol treatment induced crumpled inner membrane, an increase in periplasmic space, uneven cell surface with outer membrane vesicles, disruption of membrane structures, release of intracellular matter including chlorophylls, and eventual cell lysis in strain NIES-298, which differed from the previously proposed cell death modes. Mannitol metabolism, antioxidant-mediated protection of mannitol-induced cell lysis by, and caspase-3 induction in strain NIES-298 were not observed, suggesting that mannitol may not cause organic matter accumulation, oxidative stress, and programmed cell death in M. aeruginosa. No significant transcriptional expression was induced in strain NIES-298 by mannitol treatment, indicating that cell lysis is not induced through transcriptional responses. Mannitol-induced cell lysis may be specific to strain NIES-298 and target a specific component of strain NIES-298. This study will provide a basis for controlling M. aeruginosa growth specifically by non-toxic substances.

Insights into the synergy between functional microbes and dissolved oxygen partition in the single-stage partial nitritation-anammox granules system

The rapid start-up and stable operation of the single-stage partial nitritation-anammox (PNA) process remains a challenge in practical applications. An integrated investigation of nitrogen removal performance, sludge characteristics, activity and abundance, and microbial dynamics was implemented for 360 days via an airlift internal circulation reactor. During long-term operation, the reactor realized a stable dissolved oxygen (DO) partition and cultivated granular sludge. The nitrogen removal rate increased from 0.15 kg-N/m³/d to 1.24 kg-N/m³/d, and a high nitrogen removal efficiency of 82.6% was obtained. A stable DO partition further accelerated the bioreaction rates and enhanced the activity of functional microbes. The activities of ammonia oxidation and anammox reached 1.21 g-N/g-VSS/d and 1.43 g-N/g-VSS/d, respectively. Sludge granulation efficiently enriched the abundances of Candidatus Brocadia (7.4%) and Nitrosomonas (5.2%). These results demonstrated that efficient DO partition and stable culture of granular sludge could enhance the synergy of functional microbes for autotrophic nitrogen removal.

Sulfidogenic fluidized-bed bioreactor kinetics for co-treatment of hospital wastewater and acid mine drainage

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Bioremediation process for acidic mine water co-treatment with hospital wastewater.

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Metal precipitation reached 98% and soluble concentrations of Fe and Zn were less than 0.1 mg/l.

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SO₄²⁻ removal was above 90% in the sulfidogenic bioreactor.

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Naproxen, ibuprofen, ketoprofen, and diclofenac partially removed during the co-treatment process.

A passive co-treatment of acid mine drainage and hospital wastewater previously demonstrated a promising bioremediation viable approach for both toxic streams. The study of inhibition kinetics and microbial communities is essential to understand better the diverse species and the reaction mechanisms within the system. The kinetics and microbiology diversity in the sulfidogenic fluidized-bed reactor (at 30 °C) for co-treatment of hospital wastewater and metal-containing acidic water were examined. The alkalinity from organic oxidation raised the pH of the effluent from 2.3 to 6.1–8.2. Michaelis-Menten modeling yielded (K_m =7.3 mg/l, V_max = 0.12 mg/l min⁻¹) in the batch bioreactor treatment using sulfate-reducing bacteria. For COD oxidation, the dissolved sulfide inhibition constant (K_i) was 3.6 mg/l, and the K_i value for H₂S was 9 mg/l. The dominant species in the treatment process belong to the Proteobacteria group (especially Deltaproteobacteria). The ibuprofen and diclofenac compounds achieved the highest removal rates in the bioreactor of 58.6% and 52.3%, respectively; while, ketoprofen and naproxen of 41.9% and 46.6%, respectively. The findings in COD kinetics, sulfate-reducing bacteria abundance, and selected pharmaceutical concentration reduction provide insight into this co-treatment process's capability.

Pseudoprevotella muciniphila gen. nov., sp. nov., a mucin-degrading bacterium attached to the bovine rumen epithelium

A Gram-negative, strictly anaerobic mucin-degrading bacterium, which we designated strain E39^T, was isolated from the rumen epithelium of Korean cattle. The cells were non-motile and had a coccus morphology. Growth of strain E39^T was observed at 30–45°C (optimum, 39°C), pH 6.5–8.5 (optimum, pH 7.5), and in the presence of 0.0–1.0% (w/v) NaCl (optimum, 0.0–0.5%). Strain E39^T contained C_16:0, C_18:0, C_18:1ω9c, iso-C_15:0, and anteiso-C_15:0 as the major fatty acids. The major polar lipids were phosphatidylethanolamine, unidentified aminophospholipid, and unidentified lipids. The major respiratory isoprenoid quinones were MK-8 and MK-9. The major fermented end-products of mucin were acetate and succinate. The G+C content of the genomic DNA was 46.4 mol%. Strain E39^T was most closely related to Alloprevotella rava 81/4-12^T with an 87.3% 16S rRNA gene sequence similarity. On the basis of phenotypic, chemotaxonomic, and molecular properties, strain E39^T represents a novel genus of the family Prevotellaceae; as such, the name Pseudoprevotella muciniphila gen. nov., sp. nov. is proposed. A functional annotation of the whole genome sequences of P. muciniphila E39^T revealed that this bacterium has a putative mucin-degrading pathway and biosynthetic pathways of extracellular polymeric substances and virulence factors which enable bacteria to adhere to the epithelial cells and avoid the host’s immune responses.

Successional Dynamics of Molecular Ecological Network of Anammox Microbial Communities under Elevated Salinity

Response of microbial interactions to environmental perturbations has been a central issue in wastewater treatment system. However, the interactions among anammox microbial community under salt perturbation is still unclear. Here, we used random matrix theory (RMT)-based network analysis to investigate the dynamics of networks under elevated salinity in an anammox system. Results showed that high salinity (20 and 30 g/L NaCl) inhibited anammox performance. Salinity led to closer and more complex networks for the overall network and subnetwork of Planctomycetes and Proteobacteria, especially under low salinity (5 g/L NaCl), which could serve as a strategy to survive under salt perturbation. Planctomycetes, most dominant phylum and playing crucial roles in anammox, possessed higher proportion of competitive relationships (64.3%) under 30 g/L NaCl. OTU 109 (closely related to Ignavibacterium), the only network hub detected in the anammox system, also had larger amount of competitive relationships (27.3%) than the control (0%) under 30 g/L NaCl. Similar result was found for the most abundant keystone bacteria Candidatus Kuenenia. These increasing competitions at different taxa level could be responsible for the deterioration of nitrogen removal. Besides, all the network topological features tended to reach the values of the original network, which showed the network of microbial community could gradually adapt to the elevated salinity. Microbial network analysis adds a different dimension for our understanding of the response in microbial community to elevated salinity.

Appraisal of suspended growth process for treatment of mixture of simulated petroleum, textile, domestic, agriculture and pharmaceutical wastewater

The unrestricted discharge of domestic and industrial wastewaters along with agricultural runoff water into the environment as mixed-wastewater pose serious threat to freshwater resources in many countries. Mixed-wastewater pollution is a common phenomenon in the developing countries as the technologies to treat the individual waste streams at source are lacking due to high operational and maintenance costs. Therefore, the need to explore the potential of the suspended growth process which is a well-established process technology for biological wastewater treatment is the focus of this paper. Different wastewater constituents: representing domestic, pharmaceutical, textile, petroleum, and agricultural runoff were synthesized as a representative of mixed-wastewater and treated in two semi-continuous bioreactors (R1 & R2) operated at constant operating conditions, namely MLSS (mg/L): 4640-R1, 4440-R2, SRT: 21-d, HRT: 48-72 h, and uncontrolled pH. The system attained stable condition in day 97, with average COD, BOD and TSS reduction as 84.5%, 86.2%, and 72.2% for R1; and 85.1%, 87.9%, and 75.1% for R2, respectively. Phosphate removal on average was by 74.3% in R1 and 76.6% in R2, while average nitrification achieved in systems 1 and 2 were 56.8% and 54.7%, respectively. The biological treatment system has shown potential for improving the quality of mixed-wastewater to the state where reuse may be considered and tertiary treatment can be employed to polish the effluent quality.

Analysis of endophytic and rhizosphere bacterial diversity and function in the endangered plant Paeonia ludlowii

Paeonia ludlowii is indigenous to Tibet and has an important ecological and economic value in China. In Tibet, P. ludlowii has been used in folk medicine with relative success. Plant microbial endophytes play an important role in plant growth, health and ecological function. The diversity of endophytic bacteria associated with P. ludlowii remains poorly understood. In this study, the structure of the endophytic bacterial communities associated with different tissues, including fruits, flowers, leaves, stems, and roots, and rhizosphere soils was analyzed with Illumina MiSeq sequencing of bacterial 16S rDNA. A total of 426,240 sequences and 4847 operational taxonomic units (OTUs) were obtained. The OTUs abundance of roots was higher than that of other tissues; however, the OTUs abundance was similar among different deep soil samples. In the plant tissues, Cyanobacteria was the most abundant bacterial phylum, followed by Proteobacteria; however, the most abundant phyla were Proteobacteria and Acidobacteria in soil samples from three different layers. In addition, the diversity and richness of the microorganisms in the soil were very similar to those in roots but higher than those in other tissues of P. ludlowii. Predictive metagenome analysis revealed that endophytic bacteria play critical functional roles in P. ludlowii. This conclusion could facilitate the study of the ecological functions of endophytic bacteria and their interactions with P. ludlowii to analyze the reasons why this important medicinal plant is becoming endangered.

Effects of interchange ratio on sludge reduction and microbial community structures in an anaerobic/anoxic/oxic process with combined anaerobic side-stream reactor

Oxic-settling-anaerobic (OSA) process is effective in minimizing sludge production, by inserting an anaerobic side-stream reactor (ASSR) in the recycling bypass. Interchange ratio (IR), the quantity ratio of sludge entering the ASSR to the sludge in the main stream reactors, is one of the most important parameters for OSA process. In the present study, a laboratory-scale anaerobic/anoxic/oxic (A²/O) process combined with an ASSR (A²/O-ASSR) was operated for 366 days in parallel with a conventional A²/O process to investigate the effects of IR on sludge reduction. IR was assigned values of 5%, 8%, 10%, and 15%, and the A²/O-ASSR process achieved 14.0%, 16.0%, 24.1%, and 13.7% of sludge reduction, respectively. At the optimum IR of 10%, high through-put sequencing analysis showed that the microbes responsible for pollutant removal and ubiquitous in wastewater treatment remained predominant in the two systems, and slow-growing microbes related to hydrolysis, nitrogen and phosphorus removal increased in the A²/O-ASSR process, which probably played a key role in sludge reduction. 40.6-58.6% of sludge reduction was caused by sludge decay in the ASSR. The tiny amount of extracellular polymeric substance released in the A²/O-ASSR process was subthreshold to cause remarkable sludge reduction.

Cadmium (II) alters the microbial community structure and molecular ecological network in activated sludge system

Cadmium (II) can potentially alter the microbial community structure and molecular ecological network in activated sludge systems. In this study, we used Illumina sequencing combined with an RMT-based network approach to show the response of the microbial community and its network structure to Cd (II) in activated sludge systems. The results demonstrated that 1 mg/L Cd (II) did not have chronic negative effects on chemical oxygen demand (COD) reduction and denitrification processes, but negatively affected the nitrification process and phosphorus removal. In contrast, 10 mg/L Cd (II) adversely affected both COD and nutrient removal, and reduced the microbial diversity and changed the overall microbial community structure. The relative abundances of Nitrosomonadaceae, Nitrospira, Accumulibacter and Acinetobacter, which are involved in nitrogen removal, significantly decreased with increases in the Cd (II) concentration. In addition, molecular ecological network analysis showed that the networks sizes in the presence of higher levels of Cd (II) were smaller than in the control, but the nodes were more closely connected with neighbors. These shifts in bacterial abundance and the bacterial network structure may be responsible for the deterioration of COD and nutrient removal. Overall, this study provides new insights into the effects of Cd (II) on the bacterial community and its interactions in activated sludge systems.

Feasibility study of vertical flow constructed wetland for tertiary treatment of nanosilver wastewater and temporal-spatial distribution of pollutants and microbial community

Silver nanoparticles (AgNPs) have the potential to cause negative effects on nutrient removal in constructed wetlands (CWs), further leading to the deterioration of the water. The current work aimed to investigate the feasibility of vertical flow CW (VFCW) for tertiary treatment of AgNPs wastewater, temporal-spatial distribution of pollutants, and microbial community after 450-day exposure. Results reveal that the effluent of VFCW could still meet the discharge limits except the slightly excessive concentration of phosphorus (>0.5 mg/L) from day 390, with the average removal efficiencies of 83%, 61%, 42%, 70%, and 66% for the chemical oxygen demand, total nitrogen, ammonia nitrogen, total phosphorus, and soluble orthophosphate during 450 days, respectively. Results show that AgNPs removal was relatively stable over time, up to 96%. The temporal-spatial analysis reveals that all contaminants were mainly retained in the soil layer. The Ag concentrations in the upper soil layer and plant roots were higher than that in the lower soil layer and plant stems and leaves, respectively. Microbial sequencing analysis reveals the significant differences in the microbial community at different depths on day 450, with the dominant phyla of Proteobacteria, Acidobacteria, Chloroflexi and Bacteroidetes, and dominant genera of Halomonas and Pseudomonas. These results provide much needed knowledge for the implementation of ecological technologies for AgNPs and nutrient removal simultaneously.

Visualization and characterization of Pseudomonas syringae pv. tomato DC3000 pellicles

Cellulose, whose production is controlled by c-di-GMP, is a commonly found exopolysaccharide in bacterial biofilms. Pseudomonas syringae pv. tomato (Pto) DC3000, a model organism for molecular studies of plant-pathogen interactions, carries the wssABCDEFGHI operon for the synthesis of acetylated cellulose. The high intracellular levels of the second messenger c-di-GMP induced by the overexpression of the heterologous diguanylate cyclase PleD stimulate cellulose production and enhance air-liquid biofilm (pellicle) formation. To characterize the mechanisms involved in Pto DC3000 pellicle formation, we studied this process using mutants lacking flagella, biosurfactant or different extracellular matrix components, and compared the pellicles produced in the absence and in the presence of PleD. We have discovered that neither alginate nor the biosurfactant syringafactin are needed for their formation, whereas cellulose and flagella are important but not essential. We have also observed that the high c-di-GMP levels conferred more cohesion to Pto cells within the pellicle and induced the formation of intracellular inclusion bodies and extracellular fibres and vesicles. Since the pellicles were very labile and this greatly hindered their handling and processing for microscopy, we have also developed new methods to collect and process them for scanning and transmission electron microscopy. These techniques open up new perspectives for the analysis of fragile biofilms in other bacterial strains.

Variation in bacterial community structure of aerobic granular and suspended activated sludge in the presence of the antibiotic sulfamethoxazole

The treatment performance and bacterial community structure of conventional activated sludge and aerobic granules exposed to antibiotic sulfamethoxazole (SMX) was studied. For three months, two sets of sequencing batch reactors inoculated with conventional and granular biomass were fed with a synthetic municipal wastewater containing 2 μg/L SMX. The presence of SMX had no significant impacts on treatment performance of the reactors as well as stability of the granules. Results confirmed different bacterial community structure of flocs and granules. During the operation, variations in bacterial community structure of suspended and granular sludge were observed in all reactors. The variations in bacterial community composition due to the exposure to 2 μg/L SMX were found after two months in both suspended and granular biomass. Nitrosomonas, Pseudomonas, and Acinetobacter were detected as the genes capable of degrading SMX in both biomass types. Also, Rikenellaceae, Oscillospira, Rhodocyclaceae, Zoogloea, and Shewanella varied in abundance over the operation time. Rikenellaceae and Oscillospira were vulnerable to SMX and decreased in abundance the operation time; while Rhodocyclaceae, Zoogloea, Shewanella, and Aeromonas were found as SMX resistance genes.

New insight into sludge reduction induced by different substrate allocation strategy between oxygen and nitrate/nitrite as terminal electron acceptor

Sludge reduction based on regulating substrate allocation between catabolism and anabolism as a strategy is proposed to reduce energy and chemicals consumption during wastewater treatment. The results indicated that a sludge reduction of 14.8% and excellent nutrient removal were simultaneously achieved in the low dissolved oxygen (LDO) activated sludge system with a hydraulic retention time of 24 h at 25 °C. Denitrifiers comprised nearly 1/4 of all microorganisms in the system. These denitrifiers converted NO_x^- to N₂ obtaining a lower biomass yield. The oxidoreductase activity proteins in the LDO sample was more than twice that of the normal DO sample, indicating that catabolism was stimulated by NO_x^- when replacing O₂ as electron acceptor. Less substrate was used for cell synthesis in the LDO system. Stable sludge reduction without extra energy and chemicals inputs was achieved by regulating the substrate allocation by inducing the bacteria to utilize NO_x^- instead of O₂.

Evaluation of performance and microbial community successional patterns in an integrated OCO reactor under ZnO nanoparticle stress

An integrated OCO reactor was used to investigate the performance and microbial community successional changes under long-term exposure to relatively low levels of ZnO nanoparticles (NPs). Relatively higher concentrations of ZnO NPs (1.5 mg L⁻¹) could adversely affect the nitrogen and phosphorus removal in the reactor. The diversity and richness of the microbial communities chronically declined with an increasing concentration of ZnO NPs higher than 1.5 mg L⁻¹. With the elevated ZnO NPs, the phyla abundances of Proteobacteria, Firmicutes and Actinobacteria decreased slightly, whereas those of Bacteroidetes and Acidobacteria increased. Bacteroidetes and Proteobacteria were the predominant phyla in each phase (with a variation in abundance), together with some common taxa responses to ZnO NP stress as revealed by Venn diagram analysis. Some genera associated with the removal of nitrogen and phosphorus, such as Acinetobacter, Stenotrophomonas and Pseudomonas, decreased significantly. The present results are significant for expanding our understanding of the functional performance and microbial community successions of activated sludge which has experienced long-term exposure to environmentally relevant concentrations of ZnO NPs.

An integrated OCO reactor was used to investigate the performance and microbial community successional changes under a long-term exposure to relatively low-level ZnO nanoparticles (NPs).

Influence of CeO2 NPs on biological phosphorus removal and bacterial community shifts in a sequencing batch biofilm reactor with the differential effects of molecular oxygen

The effects of CeO₂ nanoparticles (CeO₂ NPs) on a sequencing batch biofilm reactor (SBBR) with established biological phosphorus (P) removal were investigated from the processes of anaerobic P release and aerobic P uptake. At low concentration (0.1mg/L), no significant impact was observed on total phosphorus (TP) removal after operating for 8h. However, at a concentration of 20mg/L, TP removal efficiency decreased from 83.68% to 55.88% and 16.76% when the CeO₂ NPs were added at the beginning of the anaerobic and aerobic periods, respectively. Further studies illustrated that the inhibition of the specific P release rate was caused by the reversible states of Ce³⁺ and Ce⁴⁺, which inhibited the activity of exopolyphosphatase (PPX) and transformation of poly-β-hydoxyalkanoates (PHA) and glycogen, as well as the uptake of volatile fatty acids (VFAs). The decrease in the specific P uptake rate was mainly attributed to the significantly suppressed energy generation and decreased abundance of Burkholderia caused by excess reactive oxygen species. The removal of chemical oxygen demand (COD) was not influenced by CeO₂ NPs under aerobic conditions, due to the increased abundance of Acetobacter and Acidocella after exposure. The inhibitory effects of CeO₂ NPs with molecular oxygen were reduced after anaerobic exposure due to the enhanced particle size and the presence of Ce³⁺.

Microbiote shift in sequencing batch reactors in response to antimicrobial ZnO nanoparticles

Zinc oxide nanoparticles (ZnO NPs) have been monitored in wastewater treatment plants as their potential adverse effects on functional microorganisms have been causing increasing concern.

Nutrient removal performance and microbial characteristics of a full-scale IFAS-EBPR process treating municipal wastewater

This work describes the nutrient removal performance and microbial characteristics of a full-scale integrated fixed-film activated sludge-enhanced biological phosphorus removal (IFAS-EBPR) process for municipal wastewater treatment. The polymerase chain reaction-denaturing gradient gel electrophoresis results showed that the presence of bacteria in this process, including Nitrosomonas sp., Nitrospira sp., Nitrobacter sp., Pseudomonas sp. and Acinetobacter sp., clusters. The fluorescence in situ hybridization results implied that there were more nitrifiers and denitrifiers on the biofilm carriers than in the suspended sludge, whereas more phosphorus-accumulating organisms (PAOs) resided in the suspended sludge. With the cooperation of these functional microbial populations both on the biofilm carriers and in the suspended sludge, the chemical oxygen demand (COD), NH4(+)-N, total nitrogen (TN) and total phosphorus (TP) removal efficiencies were maintained at 84, 97, 70 and 81%, and the effluent concentrations of them averaged 30, 1.0, 11.5 and 0.6 mg/L, which all satisfy the Chinese discharge standard (COD <50 mg/L, NH4(+)-N <5 mg/L, TN <15 mg/L and TP <1 mg/L), respectively. Therefore, the IFAS-EBPR process is a reliable and effective process for nutrient removal.

Identification and quantification of microbial populations in activated sludge and anaerobic digestion processes

Eight different phenotypes were studied in an activated sludge process (AeR) and anaerobic digester (AnD) in a full-scale wastewater treatment plant by means of fluorescent in situ hybridization (FISH) and automated FISH quantification software. The phenotypes were ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, denitrifying bacteria, phosphate-accumulating organisms (PAO), glycogen-accumulating organisms (GAO), sulphate-reducing bacteria (SRB), methanotrophic bacteria and methanogenic archaea. Some findings were unexpected: (a) Presence of PAO, GAO and denitrifiers in the AeR possibly due to unexpected environmental conditions caused by oxygen deficiencies or its ability to survive aerobically; (b) presence of SRB in the AeR due to high sulphate content of wastewater intake and possibly also due to digested sludge being recycled back into the primary clarifier; (c) presence of methanogenic archaea in the AeR, which can be explained by the recirculation of digested sludge and its ability to survive periods of high oxygen levels; (d) presence of denitrifying bacteria in the AnD which cannot be fully explained because the nitrate level in the AnD was not measured. However, other authors reported the existence of denitrifiers in environments where nitrate or oxygen was not present suggesting that denitrifiers can survive in nitrate-free anaerobic environments by carrying out low-level fermentation; (e) the results of this paper are relevant because of the focus on the identification of nearly all the significant bacterial and archaeal groups of microorganisms with a known phenotype involved in the biological wastewater treatment.

Biodiversity and succession of microbial community in a multi-habitat membrane bioreactor

The present study focused on establishing a multi-habitat membrane bioreactor, as well as exploring its biodiversity and succession of microbial communities. In a long-term operational period (100 days), the dissolved oxygen level of a local zone within the bioreactor decreased consistently from the original oxic state to the final anaerobic state, which led to a continuous succession of the microbial community in the bioreactor. The results revealed that the biodiversity of the microbial community in different zones simultaneously increased, with a similar microbial composition in their final successional stage. The results also indicated that the dominant species during the whole operation were distributed among 6 major phyla. At the initial operational stages, the dominant species in the anoxic-anaerobic and the oxic zones exhibited distinguished difference, whereas at the final operational stage, both zones presented nearly the same dominant microbial species and a rather similar structure in their microbial communities.

Operation performance and microbial community dynamics of phosphorus removal sludge with different electron acceptors

Operation performances of phosphorus removal sludge with different electron acceptors in three parallel SBRs were firstly compared in the present study, and the effect of post-aeration on denitrifying phosphorus removal was also studied. Moreover, community dynamics of different phosphorus removal sludge was systematically investigated with high-throughput sequencing for the first time. TP removal rates for nitrate-, nitrite-, and oxygen-based phosphorus removal sludge were 84.8, 78.5, and 87.4 %, with an average effluent TP concentration of 0.758, 0.931, and 0.632 mg/l. The average specific phosphorus release and uptake rates were 20.3, 10.8, and 21.5, and 9.43, 8.68, and 10.8 mgP/(gVSS h), respectively. Moreover, electron utilization efficiency of denitrifying phosphorus removal sludge with nitrate as electron acceptor was higher than nitrite, with P/e− were 2.21 and 1.51 mol-P/mol-e−, respectively. With the assistance of post-aeration for nitrate-based denitrifying phosphorus removal sludge, settling ability could be improved, with SVI decreased from 120 to 80 and 72 ml/g when post-aeration time was 0, 10, and 30 min, respectively. Moreover, further phosphorus removal could be achieved during post-aeration with increased aeration time. However, the anoxic phosphorus uptake was deteriorated, which was likely a result of shifted microbial community structure. Post-aeration of approximately 10 min was proposed for denitrifying phosphorus removal. Nitrate- and nitrite-based denitrifying phosphorus removal sludge exhibited similar community structure. More phosphorus accumulating organisms were enriched under anaerobic–aerobic conditions, while anaerobic–anoxic conditions were favorable for suppressing glycogen-accumulating organisms. Significant differences in pathogenic bacterial community profiles revealed in the current study indicated the potential public health hazards of non-aeration activated sludge system.

Pyrosequencing reveals higher impact of silver nanoparticles than Ag+ on the microbial community structure of activated sludge

Although the antimicrobial capabilities of silver nanoparticles (AgNPs) are widely reported, their impacts on ecologically important microbial communities are not well understood. AgNPs released from consumer products will likely enter sewer systems and wastewater treatment plants, where they would encounter (and potentially upset) activated sludge (AS), a complex ecosystem containing a variety of bacteria. Herein we address the effects of AgNPs and Ag(+) ions on the microbial community structure of AS, using pyrosequencing technology. Compared to Ag(+) amendment, a lower AgNP concentration resulted in a more pronounced effect on AS community structure, possibly reflecting a higher propensity of Ag(+) than AgNPs to be scavenged by inorganic ligands and organic matter. Furthermore, AgNPs decreased the abundance of nitrifying bacteria, which would hinder N removal, and damaged AS floc structure, which could affect sludge clarification and recycling. Overall, although released Ag(+) is known to be the critical effector of the antimicrobial activity of AgNPs, the nanoparticles apparently delivered Ag(+) to bacteria more effectively and exerted more pronounced microbial population shifts that would hinder some wastewater treatment processes.

Effects of idle time on biological phosphorus removal by sequencing batch reactors

Three identical sequencing batch reactors (SBRs) were operated to investigate the effects of various idle times on the biological phosphorus (P) removal. The idle times were set to 3 hr (R1), 10 hr (R2) and 17 hr (R3). The results showed that the idle time of a SBR had potential impact on biological phosphorus removal, especially when the influent phosphorus concentration increased. The phosphorus removal efficiencies of the R2 and R3 systems declined dramatically compared with the stable R1 system, and the P-release and P-uptake rates of the R3 system in particular decreased dramatically. The PCR-DGGE analysis showed that uncultured Pseudomonas sp. (GQ183242.1) and beta-Proteobacteria (AY823971) were the dominant phosphorus removal bacteria for the R1 and R2 systems, while uncultured gamma-Proteobacteria were the dominant phosphorus removal bacteria for the R3 system. Glycogen-accumulating organisms (GAOs), such as uncultured Sphingomonas sp. (AM889077), were found in the R2 and R3 systems. Overall, the R1 system was the most stable and exhibited the best phosphorus removal efficiency. It was found that although the idle time can be prolonged to allow the formation of intracellular polymers when the phosphorus concentration of the influent is low, systems with a long idle time can become unstable when the influent phosphorus concentration is increased.

Comparison of the bacterial communities in anaerobic, anoxic, and oxic chambers of a pilot A(2)O process using pyrosequencing analysis

A(2)O process is a sequential wastewater treatment process that uses anaerobic, anoxic, and oxic chambers for nitrogen and phosphorus removal. In this study, the bacterial communities among these chambers were compared, and the diversity of the bacteria involved in nitrogen and phosphorus removal was surveyed. A pilot-scale A(2)O process (50 m(3) day(-1)) was operated for more than 6 months, and bacterial 16S rRNA gene diversity was analyzed using pyrosequencing. A total of 7,447 bacterial sequence reads were obtained from anaerobic (1,546), anoxic (2,158), and oxic (3,743) chambers. Even though there were differences in the atmospheric condition and functionality, no prominent differences could be found in the bacterial community of the three chambers of the pilot A(2)O process. All sequence reads, which were taxonomically analyzed using the Eztaxon-e database, were assigned into 638 approved or tentative genera. Among them, about 72.2 % of the taxa were contained in the phyla Proteobacteria and Bacteroidetes. Phosphate-accumulating bacteria, Candidatus Accumulibacter phosphatis, and two other Accumulibacter were found to constitute 3.1 % of the identified genera. Ammonia-oxidizing bacteria, Nitrosomonas oligotropha, and four other phylotypes in the same family, Nitrosomonadaceae, constituted 0.2 and 0.9 %, respectively. Nitrite-oxidizing bacteria, Nitrospira defluvii, and other three phylotypes in the same family, Nitrospiraceae, constituted 2.5 and 0.1 %, respectively. In addition, Dokdonella and a phylotype of the phylum Chloroflexi, function in nitrogen and/or phosphate removal of which have not been reported in the A(2)O process, constituted the first and third composition among genera at 4.3 and 3.8 %, respectively.

Characterization of the denitrification-associated phosphorus uptake properties of "Candidatus Accumulibacter phosphatis" clades in sludge subjected to enhanced biological phosphorus removal

To characterize the denitrifying phosphorus (P) uptake properties of "Candidatus Accumulibacter phosphatis," a sequencing batch reactor (SBR) was operated with acetate. The SBR operation was gradually acclimated from anaerobic-oxic (AO) to anaerobic-anoxic-oxic (A2O) conditions by stepwise increases of nitrate concentration and the anoxic time. The communities of "Ca. Accumulibacter" and associated bacteria at the initial (AO) and final (A2O) stages were compared using 16S rRNA and polyphosphate kinase genes and using fluorescence in situ hybridization (FISH). The acclimation process led to a clear shift in the relative abundances of recognized "Ca. Accumulibacter" subpopulations from clades IIA > IA > IIF to clades IIC > IA > IIF, as well as to increases in the abundance of other associated bacteria (Dechloromonas [from 1.2% to 19.2%] and "Candidatus Competibacter phosphatis" [from 16.4% to 20.0%]), while the overall "Ca. Accumulibacter" abundance decreased (from 55.1% to 29.2%). A series of batch experiments combined with FISH/microautoradiography (MAR) analyses was performed to characterize the denitrifying P uptake properties of the "Ca. Accumulibacter" clades. In FISH/MAR experiments using slightly diluted sludge (∼0.5 g/liter), all "Ca. Accumulibacter" clades successfully took up phosphorus in the presence of nitrate. However, the "Ca. Accumulibacter" clades showed no P uptake in the presence of nitrate when the sludge was highly diluted (∼0.005 g/liter); under these conditions, reduction of nitrate to nitrite did not occur, whereas P uptake by "Ca. Accumulibacter" clades occurred when nitrite was added. These results suggest that the "Ca. Accumulibacter" cells lack nitrate reduction capabilities and that P uptake by "Ca. Accumulibacter" is dependent upon nitrite generated by associated nitrate-reducing bacteria such as Dechloromonas and "Ca. Competibacter."

Identification of a novel subgroup of uncultured gammaproteobacterial glycogen-accumulating organisms in enhanced biological phosphorus removal sludge

The presence of glycogen-accumulating organisms (GAO) has been hypothesized to be a cause of deterioration in enhanced biological phosphorus removal (EBPR) processes due to their abilities to out-compete polyphosphate-accumulating organisms (PAO). Based on 16S rRNA gene sequences, new members of uncultured gammaproteobacterial GAO (GB) were identified from sludge samples of a lab-scale sequencing batch reactor used for EBPR. The new GB formed a phylogenetic lineage (GB8) clearly distinct from the previously reported seven GB subgroups. Because the new GB8 members were not targeted by the known fluorescence in situ hybridization (FISH) oligonucleotide probes, a GB8-specific FISH probe (GB429) and a new FISH probe (GB742) targeting all eight GB subgroups were designed, and the phenotypic properties of the new GB8 members were investigated. FISH and microautoradiography approaches showed that GB429-targeted cells (GB8) were large coccobacilli (2–4 µm in size) with the ability to take up acetate under anaerobic conditions, but unable to accumulate polyphosphate under the subsequent aerobic conditions, consistent with in situ phenotypes of GB. FISH analyses on several sludge samples showed that members of GB8 were commonly detected as the majority of GB in lab- and full-scale EBPR processes. In conclusion, this study showed that members of GB8 could be a subgroup of GB with an important role in EBPR deterioration. Designs of FISH probes which hybridize with broader GB subgroups at different hierarchical levels will contribute to studies of the distributions and ecophysiologies of GB in lab- or full-scale EBPR plants.

Molecular characterization of activated sludge from a seawater-processing wastewater treatment plant

The prokaryotic community composition of activated sludge from a seawater‐processing wastewater treatment plant (Almeria, Spain) was investigated by using the rRNA approach, combining different molecular techniques such as denaturing gradient gel electrophoresis (DGGE), clone libraries and in situ hybridization (FISH and CARD‐FISH). Most of the sequences retrieved in the DGGE and the clone libraries were similar to uncultured members of different phyla. The most abundant sequence recovered from Bacteria in the clone library corresponded to a bacterium from the Deinococcus–Thermus cluster (almost 77% of the clones), and the library included members from other groups such as the Alpha, Gamma and Delta subclasses of Proteobacteria, the Bacteroidetes and Firmicutes. Concerning the archaeal clone library, we basically found sequences related to different orders of methanogenic Archaea, in correspondence with the recovered DGGE bands. Enumeration of DAPI (4′,6‐diamidino‐2‐phenylindole) stained cells from two different activated sludge samples after a mechanical flocculation disruption revealed a mean cell count of 1.6 × 10⁹ ml⁻¹. Around 94% of DAPI counts (mean value from both samples) hybridized with a Bacteria specific probe. Alphaproteobacteria were the dominant bacterial group (36% of DAPI counts), while Beta‐, Delta‐ and Gammaproteobacteria, Bacteroidetes, Actinobacteria and Firmicutes contributed to lower proportions (between 0.5–5.7% of DAPI counts). Archaea accounted only for 6% of DAPI counts. In addition, specific primers for amplification of the amoA (ammonia monooxygenase) gene were used to detect the presence of Beta, Gamma and archaeal nitrifiers, yielding positive amplifications only for Betaproteobacteria. This, together with negative in situ hybridizations with probes for well‐known nitrifiying bacteria, suggests that nitrification is performed by still undetected microorganisms. In summary, the combination of the three approaches provided different and complementary pictures of the real assemblage composition and allowed to get closer to the main microorganisms involved in key processes of seawater‐processing activated sludge.

Research advances and challenges in the microbiology of enhanced biological phosphorus removal--a critical review

Enhanced biological phosphorus removal (EBPR) is a well-established technology for removing phosphorus from wastewater. However, the process remains operationally unstable in many systems, primarily because there is a lack of understanding regarding the microbiology of EBPR. This paper presents a review of advances made in the study of EBPR microbiology and focuses on the identification, enrichment, classification, morphology, and metabolic capacity of polyphosphate- and glycogen-accumulating organisms. The paper also highlights knowledge gaps and research challenges in the field of EBPR microbiology. Based on the review, the following recommendations regarding the future direction of EBPR microbial research were developed: (1) shifting from a reductionist approach to a more holistic system-based approach, (2) using a combination of culture-dependent and culture-independent techniques in characterizing microbial composition, (3) integrating ecological principles into system design to enhance stability, and (4) reexamining current theoretical explanations of why and how EBPR occurs.

Analysis of the fine-scale population structure of "Candidatus accumulibacter phosphatis" in enhanced biological phosphorus removal sludge, using fluorescence in situ hybridization and flow cytometric sorting

To investigate the fine-scale diversity of the polyphosphate-accumulating organisms (PAO) "Candidatus Accumulibacter phosphatis" (henceforth referred to as "Ca. Accumulibacter"), two laboratory-scale sequencing batch reactors (SBRs) for enhanced biological phosphorus removal (EBPR) were operated with sodium acetate as the sole carbon source. During SBR operations, activated sludge always contained morphologically different "Ca. Accumulibacter" strains showing typical EBPR performances, as confirmed by the combined technique of fluorescence in situ hybridization (FISH) and microautoradiography (MAR). Fragments of "Ca. Accumulibacter" 16S rRNA genes were retrieved from the sludge. Phylogenetic analyses together with sequences from the GenBank database showed that "Ca. Accumulibacter" 16S rRNA genes of the EBPR sludge were clearly differentiated into four "Ca. Accumulibacter" clades, Acc-SG1, Acc-SG2, Acc-SG3, and Acc-SG4. The specific FISH probes Acc444, Acc184, Acc72, and Acc119 targeting these clades and some helpers and competitors were designed by using the ARB program. Microbial characterization by FISH analysis using specific FISH probes also clearly indicated the presence of different "Ca. Accumulibacter" cell morphotypes. Especially, members of Acc-SG3, targeted by probe Acc72, were coccobacillus-shaped cells with a size of approximately 2 to 3 mum, while members of Acc-SG1, Acc-SG2, and Acc-SG4, targeted by Acc444, Acc184, and Acc119, respectively, were coccus-shaped cells approximately 1 mum in size. Subsequently, cells targeted by each FISH probe were sorted by use of a flow cytometer, and their polyphosphate kinase 1 (ppk1) gene homologs were amplified by using a ppk1-specific PCR primer set for "Ca. Accumulibacter." The phylogenetic tree based on sequences of the ppk1 gene homologs was basically congruent with that of the 16S rRNA genes, but members of Acc-SG3 with a distinct morphology comprised two different ppk1 genes. These results suggest that "Ca. Accumulibacter" strains may be diverse physiologically and ecologically and represent distinct populations with genetically determined adaptations in EBPR systems.

Molecular diversity of a North Carolina wastewater treatment plant as revealed by pyrosequencing

We report the results of pyrosequencing of DNA collected from the activated sludge basin of a wastewater treatment plant in Charlotte, NC. Using the 454-FLX technology, we generated 378,601 sequences with an average read length of 250.4 bp. Running the 454 assembly algorithm over our sequences yielded very poor assembly, with only 0.3% of our sequences participating in assembly of significant contigs. Of the 117 contigs greater than 500 bp long that were assembled, the most common annotations were to transposases and hypothetical proteins. Comparing our sequences to known microbial genomes showed nonspecific recruitment, indicating that previously described taxa are only distantly related to the most abundant microbes in this treatment plant. A comparison of proteins generated by translating our sequence set to translations of other sequenced microbiomes shows a distinct metabolic profile for activated sludge with high counts for genes involved in metabolism of aromatic compounds and low counts for genes involved in photosynthesis. Taken together, these data document the substantial levels of microbial diversity within activated sludge and further establish the great utility of pyrosequencing for investigating diversity in complex ecosystems.

Caenimonas koreensis gen. nov., sp. nov., isolated from activated sludge

A Gram-negative, rod-shaped bacterium, designated strain EMB320T, was isolated from activated sludge performing enhanced biological phosphorus removal in a sequencing batch reactor. The isolate was strictly aerobic and non-motile. Growth was observed between 10 and 35 degrees C (optimum 30 degrees C) and between pH 6.0 and 9.0 (optimum pH 7.0-8.0). The predominant cellular fatty acids of strain EMB320T were C16 : 0, C18 : 1omega7c and summed feature 3 (C16 : 1omega7c and/or iso-C15 : 0 2-OH). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Strain EMB320T contained ubiquinone-8 (Q-8) as the major respiratory quinone system and 2-hydroxyputrescine and putrescine as the major polyamines, which suggests that it belongs to the Betaproteobacteria. The G+C content of the genomic DNA was 62.7 mol%. Comparative 16S rRNA gene sequence analysis showed that strain EMB320T formed a phyletic lineage distinct from other genera within the family Comamonadaceae. On the basis of chemotaxonomic data and molecular properties, strain EMB320T represents a novel genus and species within the family Comamonadaceae, for which the name Caenimonas koreensis sp. nov. is proposed. The type strain of Caenimonas koreensis is EMB320T (=KCTC 12616T =DSM 17982T).

Brevundimonas aveniformis sp. nov., a stalked species isolated from activated sludge

A Gram-negative, rod-like, stalk-producing bacterium, designated strain EMB102(T), was isolated from activated sludge that performed enhanced biological phosphorus removal in a sequencing batch reactor. Cells without stalks were motile with single polar flagella, but cells that did produce stalks were non-motile and lacked polar flagella. Growth of strain EMB102(T) was observed at temperatures between 15 and 35 degrees C (optimum, 30 degrees C) and between pH 6.0 and 9.0 (optimum, pH 7.5-8.5). The predominant fatty acids of strain EMB102(T) were C(18 : 1) omega 7c, C(16 : 0) and C(15 : 0). The predominant polar lipid was phosphatidylglycerol. The G+C content of the genomic DNA was 64.1 mol% and the major quinone was Q-10. Comparative 16S rRNA gene sequence analyses showed that strain EMB102(T) formed a distinct phyletic lineage within the genus Brevundimonas. The levels of 16S rRNA gene sequence similarity between the type strains of Brevundimonas species ranged from 95.8 to 97.5 %. DNA-DNA relatedness levels between the EMB102(T) and closely related Brevundimonas species were below 15.0 %. On the basis of chemotaxonomic data and molecular properties, strain EMB102(T) represents a novel species within the genus Brevundimonas, for which the name Brevundimonas aveniformis sp. nov. is proposed. The type strain is EMB102(T) (=KCTC 12609(T)=DSM 17977(T)).

Hydrogenophaga caeni sp. nov., isolated from activated sludge

A Gram-negative bacterium, designated strain EMB71T, was isolated from activated sludge used for enhanced biological phosphorus removal in a sequencing batch reactor. The cells of the isolate were facultatively aerobic, motile rods with single polar flagella. Growth was observed to occur at 15–35 °C (optimally at 30 °C) and at pH 6.0–9.0 (optimally at pH 7.0–8.0). The predominant fatty acids of strain EMB71T were C16 : 0 and summed feature 3 (C16 : 1 ω7c and/or iso-C15 : 0 2-OH), and the polar lipids comprised a large amount of phosphatidylethanolamine and a small amount of diphosphatidylglycerol. The G+C content of the genomic DNA was 61.6 mol % and the major quinone was Q-8. Comparative 16S rRNA gene sequence analyses showed that strain EMB71T formed a phyletic lineage with the genus Hydrogenophaga within the family Comamonadaceae. The levels of 16S rRNA gene sequence similarity with respect to the type strains of Hydrogenophaga species ranged from 95.1 to 96.9 %. On the basis of the phenotypic, chemotaxonomic and molecular data, strain EMB71T represents a novel species of the genus Hydrogenophaga, for which the name Hydrogenophaga caeni sp. nov. is proposed. The type strain is EMB71T (=KCTC 12613T=DSM 17962T).

Simplicispira limi sp. nov., isolated from activated sludge

A Gram-negative, motile, rod-shaped bacterium, designated strain EMB325T, was isolated from activated sludge that performed enhanced biological phosphorus removal in a sequencing batch reactor. The predominant fatty acids of strain EMB325T were summed feature 3 (C16 : 1 ω7c and/or iso-C15 : 0 2-OH), C16 : 0, C18 : 1 ω7c and C18 : 1 ω7c 11-methyl. The strain contained phosphatidylethanolamine and diphosphatidylglycerol as polar lipids. The G+C content of the genomic DNA was 63.3 mol%. The major quinone was Q-8. Phylogenetic analysis of 16S rRNA gene sequences showed that strain EMB325T formed a phyletic lineage with members of the genus Simplicispira and was most closely related to Simplicispira psychrophila LMG 5408T and Simplicispira metamorpha DSM 1837T with similarities of 98.1 and 97.9 %, respectively. Levels of DNA–DNA relatedness between strain EMB325T and S. psychrophila LMG 5408T and S. metamorpha DSM 1837T were 28 and 23 %, respectively. On the basis of chemotaxonomic data and molecular characteristics, strain EMB325T is considered to represent a novel species within the genus Simplicispira, for which the name Simplicispira limi sp. nov. is proposed. The type strain is EMB325T (=KCTC 12608T=DSM 17964T).

Comparing results of cultured and uncultured biological methods used in biological phosphorus removal

Increasing attention has been paid to phosphate-accumulating organisms (PAOs) for their important role in biological phosphorus removal. In this study, microbial communities of PAOs cultivated under different carbon sources (sewage, glucose, and sodium acetate) were investigated and compared through culture-dependent and culture-independent methods, respectively. The results obtained using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified 16S rDNA fragments revealed that the diversity of bacteria in a sewage-fed reactor (1#) was much higher than in a glucose-fed one (2#) and a sodium acetate-fed one (3#); there were common PAOs in three reactors fed by different carbon sources. Five strains were separated from three systems by using a phosphate-rich medium; they were from common bacteria isolated and three isolates could not be found in DGGE profile at all. Two isolates had good phosphorus removal ability. When the microbial diversity was studied, the molecular biological method was better than the culture-dependent one. When phosphorus removal characteristics were investigated, culture-dependent approach was more effective. Thus a combination of two methods is necessary to have a comprehensive view of PAOs.

Flavobacterium croceum sp. nov., isolated from activated sludge

A Gram-negative, non-motile, rod-shaped bacterium, designated strain EMB47(T), was isolated from activated sludge performing enhanced biological phosphorus removal in a sequencing batch reactor. Growth was observed between 10 and 40 degrees C (optimum, 25-35 degrees C) and between pH 5.0 and 8.5 (optimum, pH 7.5-8.0). The predominant fatty acids of strain EMB47(T) were iso-C(16 : 0) 3-OH, iso-C(15 : 1) G, C(15 : 0), iso-C(15 : 0), iso-C(14 : 0) and iso-C(16 : 0) and it contained phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylcholine as polar lipids. The G+C content of the genomic DNA was 40.8 mol% and the major quinone was MK-6. Comparative 16S rRNA gene sequence analyses showed that strain EMB47(T) formed a distinct phyletic line within the genus Flavobacterium. The levels of 16S rRNA gene sequence similarity with respect to Flavobacterium species were below 94.7 %. On the basis of the phenotypic, chemotaxonomic and molecular data, strain EMB47(T) represents a novel species within the genus Flavobacterium, for which the name Flavobacterium croceum sp. nov. is proposed. The type strain is EMB47(T) (=KCTC 12611(T)=DSM 17960(T)).

Runella limosa sp. nov., isolated from activated sludge

A Gram-negative bacterium, designated strain EMB111T, was isolated from activated sludge performing enhanced biological phosphorus removal in a sequencing batch reactor. Cells were long and rod-shaped. The isolate was strictly aerobic and non-motile. The strain grew optimally at 25–30 °C and pH 7.5–8.0. The predominant fatty acids of strain EMB111Twere iso-C15 : 0, C16 : 1ω5c, iso-C17 : 03-OH, iso-C15 : 03-OH, C16 : 03-OH, C16 : 0and summed feature 3 (C16 : 1ω7cand/or iso-C15 : 02-OH). The strain contained a large amount of phosphatidylglycerol and small amounts of two unknown phospholipids (PL1, PL2) as the polar lipids. The major isoprenoid quinone was menaquinone-7. The G+C content of the genomic DNA was 42.7 mol%. Phylogenetic analysis showed that strain EMB111Tformed a phyletic cluster with members of the genusRunellawithin the familyFlexibacteraceaeand was most closely related toRunella slithyformisATCC 29530Twith a 16S rRNA gene sequence similarity of 94.8 %. On the basis of chemotaxonomic data and molecular properties, strain EMB111Trepresents a novel species within the genusRunella, for which the nameRunella limosasp. nov. is proposed. The type strain is EMB111T(=KCTC 12615T=DSM 17973T).

Paenibacillus gansuensis sp. nov., isolated from desert soil of Gansu Province in China

A Gram-positive, endospore-forming, rod-shaped bacterium, designated strain B518(T), was isolated from a desert-soil sample from Gansu Province in China. The isolate was strictly aerobic and was motile by means of several flagella. The strain grew optimally at 35-40 degrees C and at pH 7.0-7.5. The predominant fatty acids of strain B518(T) were anteiso-C(15 : 0), C(16 : 0), anteiso-C(17 : 0), iso-C(16 : 0) and iso-C(15 : 0). The G+C content of the genomic DNA was 50 mol% and the predominant quinone was MK-7. Comparative 16S rRNA gene sequence analyses showed that strain B518(T) formed a distinct phyletic line within the genus Paenibacillus and was most closely related to Paenibacillus chitinolyticus IFO 15660(T), with a 16S rRNA gene sequence similarity of 95.8 %. The levels of 16S rRNA gene sequence similarity with respect to other type strains of Paenibacillus species were below 95.1 %. On the basis of the chemotaxonomic data and molecular properties, strain B518(T) represents a novel species within the genus Paenibacillus, for which the name Paenibacillus gansuensis sp. nov. is proposed. The type strain is B518(T) (=KCTC 3950(T)=DSM 16968(T)).

Changes in respiratory quinone profiles of enhanced biological phosphorus removal activated sludge under different influent phosphorus/carbon ratio conditions

Changes in the microbial community of an enhanced biological phosphorus removal (EBPR) activated sludge system under different influent phosphorus/carbon (P/C) ratio conditions were investigated through evaluation of population respiratory quinone profiles. A total of 13 types of respiratory quinone homologs consisting of 3 types of ubiquinones (UQ) and 10 types of menaquinones (MK) were identified in this study. The dominant quinones were UQ-8 and MK-7 throughout the operational period. A higher P/C ratio (0.1) in the influent stimulated an increase in the mole fractions of UQ-8, MK-7, MK-8(H(4)), MK-9(H(4)) and MK-8(H(8)), suggesting that actinobacterial polyphosphate-accumulating organisms (PAO) containing partially hydrogenated MK, mainly MK-8(H(4)), were contributing to EBPR. However, when the P/C ratio gradually decreased from 0.1 to 0.01, the mole fractions of UQ-8 increased from 0.46 to 0.58, while MK-7, MK-8(H(2)), MK-8(H(4)), MK-9(H(4)), MK-8(H(8)) and MK-9(H(6)) markedly decreased. These changes in the respiratory quinone profiles suggest that glycogen-accumulating organisms corresponding to some Gammaproteobacteria had become dominant populations with a decrease in actinobacterial PAO. On the other hand, increasing abruptly the P/C ratio to 0.1 further caused an increase in the mole fraction of UQ-8, indicating that Rhodocyclus-related organisms were important PAO.

Nitrification performance and microbial community dynamics in a submerged membrane bioreactor with complete sludge retention

A submerged membrane bioreactor (MBR) supplied with inorganic ammonium-bearing wastewater (NH(4)(+)-N, 500 mgl(-1)) was operated for 260 days without sludge purge under decreased hydraulic retention times (HRT) through six steps (from 30 to 5h). Almost complete nitrification was obtained at a volumetric loading rate (VLR)1.2g NH(4)(+)-Nl(-1)day(-1). The sludge nitrification activities were evaluated at each stage. The specific ammonium oxidizing rate (SAOR) decreased from the initial 0.45 to 0.15 kg NH(4)(+)-Nkg(-1)MLSSday(-1) in the last four stages, while the specific nitrate forming rate (SNFR) increased from 0.17 to 0.39 kg NO(3)(-)-Nkg(-1)MLSSday(-1) at the third stage, and then decreased to below 0.1 kg NO(3)(-)-Nkg(-1)MLSSday(-1) from the fourth stage. Microbial population dynamics was investigated by a combination of the MPN method, fluorescence in situ hybridization (FISH) and quinone profiles. During the experiment, although the MLSS increased gradually from 4.5 to 11.5 gl(-1), the number of ammonia-oxidizing bacteria (AOB) decreased from 10(9)l(-1) at the third stage to 10(7)l(-1) in the last two stages, and that of nitrite-oxidizing bacteria (NOB) decreased gradually from 10(8)l(-1) at the second stage (HRT of 20 h) to the final 10(5)l(-1). FISH results showed that the active cells decreased gradually with time from about 60 to 20% in the last two stages, and most of sludge was inert cells. The sum of nitrifiers occupied only about 10% of the total bacteria number in the last stage even though only ammonium-bearing inorganic wastewater was fed in. Nitrosomonas sp. and Nitrospira sp. were confirmed by FISH as the dominant nitrifying genera responsible for ammonia and nitrite oxidation, respectively. In the mean time, a small ratio of Nitrobacter sp. also existed in the system. FISH analysis matched better with the batch activity test results than did the MPN techniques. Quinone profiles revealed that the dominant ubiquinone was ubiquinone-8 (UQ-8), ranging from 84 to 66%, followed by UQ-10 of 7-13%, UQ-7 of 3-5% and UQ-9 of 1.6-2.6%. The dominant menaquinone in the MBR was menaquinone-7 (MK-7) followed by MK-6, MK-8 and MK-8 (H(2)). With the prolongation of operation, the percentage of menaquinones increased from 8 to 14%. The use of the polyphasic approach gave some new insight on variations of microbial community structures.

Supercritical carbon dioxide extraction of ubiquinones and menaquinones from activated sludge

Supercritical CO2 (scCO2) extraction, with methanol as modifier, was applied to the determination of ubiquinones and menaquinones in activated sludge. Four ubiquinones and 12 menaquinones species were identified based on retention time and UV spectrum in 0.1g dried activated sludge. The optimum extraction conditions were at a pressure of 25 MPa, a temperature of 55 degrees C, and 10% (v/v) methanol for 15 min. At this condition, the concentrations of extracted ubiquinones and menaquinones were found to be 0.181 and 0.326 micromol/g-dry-cell, respectively. The results were comparable with those obtained by organic solvent extraction based on diversity and dissimilarity indices. Furthermore, the method was evaluated in term of repeatability, which resulted in an RSD of < or =10%. The experimental results have demonstrated the technique to be simple, fast, and with less consumption of organic solvents. This work shows the potential application of supercritical CO2 extraction to microbial community analysis using quinone profile.