RESUMEN
In this study, we used a high-throughput sequencing technology to survey the dry-wet seasonal change characteristics of soil ammonia-oxidizing bacteria (AOB) communities in the three restoration stages [i.e., Mallotus paniculatus community (early stage), Millettia leptobotrya community (middle stage), and Syzygium oblatum community (later stage)] of Xishuangbanna tropical forest ecosystems. We analyzed the effects of soil physicochemical characteristics on AOB community composition and diversity during tropical forest restoration. The results showed that tropical forest restoration significantly affected the relative abundance of dominant AOB phyla and their dry-wet seasonal variation. The maximum relative abundance of Proteobacteria (71.3%) was found in the early recovery stage, while that of Actinobacteria was found in the late recovery stage (1.0%). The abundances of Proteobacteria and Actinobacteria had the maximum ranges of dry-wet seasonal variation in the early and late stages, respectively. The abundance of dominant AOB genera and its dry-wet seasonal variation varied across tropical forest restoration stages. The maximum average relative abundance of Nitrosospira and Nitrosomonas in the late recovery stage was 66.2% and 1.5%, respectively. In contrast, the abundance of Nitrosovibrio reached its maximum (25.6%) in the early recovery stage. The maximum dry-wet seasonal variation in relative abundance of Nitrosospira and Nitrosomonas occurred in the early recovery stage, while that of Nitrosovibrio occurred in the middle recovery stage. The Chao1, Shannon, and Simpson diversity indices of AOB communities increased along the restoration stages, which were significantly higher in the wet season than in the dry season. The results of canonical correspondence analysis showed that soil easily oxidized carbon was the main factor controlling AOB community diversity and Actinobacteria abundance. Soil bulk density and temperature were the main factors affecting Proteobacteria abundance. Soil pH, microbial biomass carbon, water content, ammonium nitrogen, bulk density, and temperature were the main factors controlling the abundances of Nitrosospira, Nitrosomonas, and Nitrosovibrio. Therefore, tropical forest restoration can regulate the change of relative abundance of dominant AOB taxa via mediating the changes of soil temperature, bulk density, and readily oxidized carbon, leading to an increase in soil AOB community diversity.
Asunto(s)
Amoníaco , Bacterias , Bosques , Oxidación-Reducción , Estaciones del Año , Microbiología del Suelo , Clima Tropical , Amoníaco/metabolismo , Bacterias/clasificación , Bacterias/metabolismo , Bacterias/aislamiento & purificación , Bacterias/genética , Bacterias/crecimiento & desarrollo , Proteobacteria/aislamiento & purificación , Proteobacteria/clasificación , Proteobacteria/metabolismo , Proteobacteria/genética , China , Conservación de los Recursos Naturales , Restauración y Remediación Ambiental/métodos , Nitrosomonas/metabolismo , Nitrosomonas/clasificación , Nitrosomonas/crecimiento & desarrollo , Bosque LluviosoRESUMEN
Exploring differences in nitrification within adjacent sedimentary structures of ridges and runnels on the Brouage mudflat, France, we quantified Potential Nitrification Rates (PNR) alongside amoA genes and transcripts. PNR was lower in ridges (≈1.7 fold-lower) than runnels, despite higher (≈1.8 fold-higher) ammonia-oxidizing bacteria (AOB) abundance. However, AOB were more transcriptionally active in runnels (≈1.9 fold-higher). Sequencing of amoA genes and transcripts revealed starkly contrasting profiles with transcripts from ridges and runnels dominated (≈91 % in ridges and ≈98 % in runnels) by low abundant (≈4.6 % of the DNA community in runnels and ≈0.8 % in ridges) but highly active phylotypes. The higher PNR in runnels was explained by higher abundance of this group, an uncharacterised Nitrosomonas sp. cluster. This cluster is phylogenetically similar to other active ammonia-oxidizers with worldwide distribution in coastal environments indicating its potential, but previously overlooked, contribution to ammonia oxidation globally. In contrast DNA profiles were dominated by highly abundant but low-activity clusters phylogenetically distinct from known Nitrosomonas (Nm) and Nitrosospira (Ns). This cluster is also globally distributed in coastal sediments, primarily detected as DNA, and often classified as Nitrosospira or Nitrosomonas. We therefore propose to classify this cluster as Ns/Nm. Our work indicates that low abundant but highly active AOB could be responsible for the nitrification globally, while the abundant AOB Ns/Nm may not be transcriptionally active, and as such account for the lack of correlation between rate processes and gene abundances often reported in the literature. It also raises the question as to what this seemingly inactive group is doing?
Asunto(s)
Amoníaco , Nitrificación , Nitrosomonas , Oxidación-Reducción , Amoníaco/metabolismo , Francia , Nitrosomonas/metabolismo , Nitrosomonas/genética , Sedimentos Geológicos/microbiología , FilogeniaRESUMEN
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.
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Reactores Biológicos , Nitritos , Nitrógeno , Aguas del Alcantarillado , Aguas del Alcantarillado/microbiología , Nitritos/metabolismo , Reactores Biológicos/microbiología , Nitrógeno/metabolismo , Oxidación-Reducción , Eliminación de Residuos Líquidos/métodos , Anaerobiosis , Nitrosomonas/metabolismo , Compuestos de Amonio/metabolismoRESUMEN
In order to solve the complicated control of dissolved oxygen (DO) for partial nitrification in bioreactors treating high NH4+-N wastewater, a large height-diameter ratio anammox pre-reactor system was developed. And in this reactor, NO2--N accumulation rate can reach 85.76% by alternate feeding with high NH4+-N wastewater (150 mg NH4+-N/L) and low NH4+-N wastewater (50 mg c) with low DO (0.19 mg/L-0.62 mg/L). Based on 16S rRNA identification technology, it was found that Nitrosomonas had a significant effect on NH4+-N oxidization in this study. And when the reactor treated higher concentration wastewater (250â mg NH4+-N/L), the growth rate of Nitrosomonas was higher than that of Nitrospira (nitrite-oxidizing bacteria, NOB), which was conducive to improving the NO2--N accumulation rate and realizing partial nitrification stably. It was also found that the material exchange frequency of the microbial flora during alternate feeding with different NH4+-N concentration wastewaters was higher than that during feeding with higher NH4+-N concentration wastewater (250 mg/L) by Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolism pathways analysis. This study can provide valuable insights and lay the foundation for building anammox pre-reactors.
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Amoníaco , Nitrificación , Amoníaco/metabolismo , Aguas Residuales , ARN Ribosómico 16S/genética , Oxidación-Reducción , Bacterias/genética , Bacterias/metabolismo , Reactores Biológicos/microbiología , Nitritos/metabolismo , Nitrosomonas/metabolismo , Nitrógeno/metabolismoRESUMEN
With the increasing complexity of influent composition in wastewater treatment plants, the potential stimulating effects of refractory organic matter in wastewater on growth characteristics and genera conversion of nitrifying bacteria (ammonium-oxidizing bacteria [AOB] and nitrite-oxidizing bacteria [NOB]) need to be further investigated. In this study, domestic wastewater was co-treated with landfill leachate in the lab-scale reactor, and the competition and co-existence of NOB genera Nitrotoga and Nitrospira were observed. The results demonstrated that the addition of landfill leachate could induce the growth of Nitrotoga, whereas Nitrotoga populations remain less competitive in domestic wastewater operation. In addition, the refractory organic matter in the landfill leachate also would have a potential stimulating effect on the maximum specific growth rate of AOB genus Nitrosomonas (µmax, aob). The µmax, aob of Nitrosomonas in the control group was estimated to be 0.49 d-1 by fitting the ASM model, and the µmax, aob reached 0.66-0.71 d-1 after injection of refractory organic matter in the landfill leachate, while the maximum specific growth rate of NOB (µmax, nob) was always in the range of 1.05-1.13 d-1. These findings have positive significance for the understanding of potential stimulation on nitrification processes and the stable operation of innovative wastewater treatment process.
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Compuestos de Amonio , Nitrosomonas europaea , Contaminantes Químicos del Agua , Aguas Residuales , Amoníaco , Oxidación-Reducción , Nitritos , Nitrificación , Nitrosomonas , Bacterias , Reactores Biológicos/microbiología , NitrógenoRESUMEN
Nitrosomonas europaea, an aerobic ammonia oxidizing bacterium, is responsible for the first and rate-limiting step of the nitrification process, and their ammonia oxidation activities are critical for the biogeochemical cycling and the biological nitrogen removal of wastewater treatment. In the present study, N. europaea cells were cultivated in the inorganic or organic media (the NBRC829 and the nutrient-rich, NR, media, respectively), and the cells proliferated in the form of planktonic and biofilm in those media, respectively. The N. europaea cells in the biofilm growth mode produced larger amounts of the extracellular polymeric substances (EPS), and the composition of the EPS was characterized by the chemical analyses including Fourier transform infrared spectroscopy (FT-IR) and 1H-nuclear magnetic resonance (NMR) measurements. The RNA-Seq analysis of N. europaea in the biofilm or planktonic growth mode revealed that the following gene transcripts involved in central nitrogen metabolisms were abundant in the biofilm growth mode; amo encoding ammonia monooxygenase, hao encoding hydroxylamine dehydrogenase, the gene encoding nitrosocyanine, nirK encoding copper-containing nitrite reductase. Additionally, the transcripts of the pepA and wza involved in the bacterial floc formation and the translocation of EPS, respectively, were also abundant in the biofilm-growth mode. Our study was first to characterize the EPS production and transcriptome of N. europaea in the biofilm and planktonic growth mode.
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Nitrosomonas europaea , Nitrosomonas europaea/genética , Nitrosomonas europaea/metabolismo , Amoníaco/metabolismo , Matriz Extracelular de Sustancias Poliméricas/metabolismo , Oxidación-Reducción , Transcriptoma/genética , Plancton/genética , Plancton/metabolismo , Espectroscopía Infrarroja por Transformada de Fourier , Biopelículas , Bacterias/metabolismo , Nitrosomonas/metabolismoRESUMEN
In this study, a laboratory-scale partial nitrification reactor (PN reactor) was used to treat high-ammonia-nitrogen wastewater, by changing the influent NH4+-N conversion rate as the main operating strategy, to investigate the upper limit of its NH4+-N conversion rate (ACR) and explore its feasibility as an anammox pre-process. During the experiment, PN reactor was successfully activated in only 10 days. The PN reactor reached the highest ACR value of approximately 10.24 kg N/(m3 · day) when the influent ACR was 16.57 kg N/(m3 · day), and the ammonia conversion efficiency (ACE) was 61.78% at this time. The ratio of [NO2--N]Eff/[NH4+-N]Eff was approximately 1.37 which was close to the theoretical ratio of 1.32. And feasibility exploration experiment proved that it was feasible to use this PN reactor as a pre-process of anammox. The PCR-DGGE results showed that the dominant phylum and genus in the reactor during the ACR experiment were Proteobacteria and Nitrosomonas, respectively. With the increase in the ACR, the relative concentration of Nitrosomonas sp. G1 increased from 15 to 40%. This indicates that its abundance is directly correlated with the increase in the ACR. High-throughput sequencing showed that increasing the ACR of the PN reactor greatly reduced the diversity and abundance of the system microbial community structure and changed the dominant phylum and genus; however, the stability of the system was not disrupted. High-throughput sequencing experiments showed that the abundance value of nitrosation enzymes accounted for 91.62%, which was positively correlated with the expression of nitrification genes in the genus Nitrosomonas.
Asunto(s)
Amoníaco , Oxidación Anaeróbica del Amoníaco , Reactores Biológicos/microbiología , Oxidación-Reducción , Aguas Residuales , Nitrificación , Nitrógeno/metabolismo , Nitrosomonas , Aguas del Alcantarillado/microbiología , DesnitrificaciónRESUMEN
Antibiotic resistance genes (ARGs) have recently become an important public health problem and therefore several studies have characterized ARG composition and distribution. However, few studies have assessed their impact on important functional microorganisms in the environment. Therefore, our study sought to investigate the mechanisms through which multidrug-resistant plasmid RP4 affected the ammonia oxidation capacity of ammonia-oxidizing bacteria, which play a key role in the nitrogen cycle. The ammonia oxidation capacity of N. europaea ATCC25978 (RP4) was significantly inhibited, and NO and N2O were produced instead of nitrite. Our findings demonstrated that the decrease in electrons from NH2OH decreased the ammonia monooxygenase (AMO) activity, leading to a decrease in ammonia consumption. In the ammonia oxidation process, N. europaea ATCC25978 (RP4) exhibited ATP and NADH accumulation. The corresponding mechanism was the overactivation of Complex â , ATPase, and the TCA cycle by the RP4 plasmid. The genes encoding TCA cycle enzymes related to energy generation, including gltA, icd, sucD, and NE0773, were upregulated in N. europaea ATCC25978 (RP4). These results demonstrate the ecological risks of ARGs, including the inhibition of the ammonia oxidation process and an increased production of greenhouse gases such as NO and N2O.
Asunto(s)
Nitrosomonas europaea , Nitrosomonas europaea/genética , Amoníaco , Transporte de Electrón , Oxidación-Reducción , Nitritos , NitrosomonasRESUMEN
RNA-sequencing for whole transcriptome analysis requires high-quality RNA in adequate amounts, which can be difficult to generate with low-biomass-producing bacteria where sample volume is limited. We present an RNA extraction protocol for low-biomass-producing autotrophic bacteria Nitrosomonas europaea and Nitrobacter winogradskyi cultures. We describe steps for sample collection, lysozyme-based enzymatic lysis, and a commercial silica-column-based RNA extraction. We then detail evaluation of RNA yield and quality for downstream applications such as RNA-Seq. For complete details on the use and execution of this protocol, please refer to Verbeelen et al.1.
Asunto(s)
Nitrobacter , Nitrosomonas europaea , Nitrosomonas europaea/genética , Nitrosomonas/genética , Transcriptoma/genética , Biomasa , Bacterias/genética , ARNRESUMEN
Members of the genus Nitrosomonas are major ammonia oxidizers that catalyse the first step of nitrification in various ecosystems. To date, six subgenus-level clades have been identified. We have previously isolated novel ammonia oxidizers from an additional clade (unclassified cluster 1) of the genus Nitrosomonas. In this study, we report unique physiological and genomic properties of the strain PY1, compared with representative ammonia-oxidising bacteria (AOB). The apparent half-saturation constant for total ammonia nitrogen and maximum velocity of strain PY1 were 57.9 ± 4.8 µM NH3 + NH4 + and 18.5 ± 1.8 µmol N (mg protein)-1 h-1 , respectively. Phylogenetic analysis based on genomic information revealed that strain PY1 belongs to a novel clade of the Nitrosomonas genus. Although PY1 contained genes to withstand oxidative stress, cell growth of PY1 required catalase to scavenge hydrogen peroxide. Environmental distribution analysis revealed that the novel clade containing PY1-like sequences is predominant in oligotrophic freshwater. Taken together, the strain PY1 had a longer generation time, higher yield and required reactive oxygen species (ROS) scavengers to oxidize ammonia, compared with known AOB. These findings expand our knowledge of the ecophysiology and genomic diversity of ammonia-oxidising Nitrosomonas.
Asunto(s)
Amoníaco , Nitrosomonas , Amoníaco/metabolismo , Filogenia , Nitrosomonas/genética , Nitrosomonas/metabolismo , Ecosistema , Oxidación-Reducción , Bacterias/genética , Bacterias/metabolismo , GenómicaRESUMEN
In the first and limiting step of nitrification, ammonia (NH3) is oxidised to nitrite (NO2-) by the action of some prokaryotes, including bacteria of the Nitrosomonas genus. A potential approach to nitrification inhibition would be through the application of phages, but until now this method has been unexplored and no virulent phages that infect nitrifying bacteria have been described. In this study, we report the isolation of the first phage infecting some Nitrosomonas species. This polyvalent virulent phage (named ΦNF-1) infected Nitrosomonas europaea, Nitrosomonas communis, and Nitrosomonas nitrosa. Phage ΦNF-1 has the morphology of the Podoviridae family, a dsDNA genome of 41,596 bp and a 45.1 % GC content, with 50 predicted open reading frames. Phage ΦNF-1 was found to inhibit bacterial growth and reduce NH4+ consumption in the phage-treated cultures. The application of phages as biocontrol agents could be a useful strategy for nitrification inhibition without the restrictions associated with chemical inhibitors.
Asunto(s)
Bacteriófagos , Nitrosomonas europaea , Bacteriófagos/genética , Nitrosomonas , Bacterias , Nitritos , AmoníacoRESUMEN
This work comprehensively deciphered the effect of free nitrous acid (FNA) on the microbial community, inhibitory kinetics, and nitrifiers in nitritation process. Nitritation was first successfully achieved through selective inhibition of free ammonia (FA) on nitrite oxidizers (NOB). Then, batch tests clearly showed that FNA significantly inhibits the ammonia oxidation rate (rsu) and the growth rate (µ) of ammonia oxidizers (AOB), which was well described by the Hellinga model (KI = 0.222 mg·L-1). The structural equation model indicated that FNA was significantly and negatively associated with rsu, µ, Nitrosomonas, Commamons, Nitrospira, and Nitrotoga and positively correlated with Paracoccus. Furthermore, Nitrosomonas significantly drove the ammonia utilization and growth of AOB and was identified as the most important functional biomarker indicating the nitritation in response to FNA levels using random forest model. This study provides helpful information on the kinetics of the mechanism underlying the FNA inhibition on nitrification.
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Microbiota , Ácido Nitroso , Amoníaco , Oxidación-Reducción , Reactores Biológicos , Nitritos , Nitrosomonas , Nitrificación , Aguas del AlcantarilladoRESUMEN
The ammonia oxidation process driven by microorganisms is an essential source of nitrous oxide (N2O) and nitric oxide (NO) emissions. However, few evaluations have been performed on the changes in the community structure and abundance of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) under substituting portion of chemical fertilizers with organic manure (organic substitution) and their relative contribution to the ammonia oxidation process. Here, five long-term fertilization strategies were applied in field (SN: synthetic fertilizer application; OM: organic manure; M1N1: substituting 50 % of chemical N fertilizer with organic manure; M1N4: substituting 20 % of chemical N fertilizer with organic manure; and CK: no fertilizer). We investigated the response characteristics of AOB and AOA community structures by selective inhibitor shaking assays and high-throughput sequencing and further explained their relative contribution to the ammonia oxidation process during three consecutive years of vegetable production. Compared to SN and M1N4, the potential of ammonia oxidation (PAO) was significantly reduced by 26.4 % and 22.3 % in OM and 9.5 % and 4.4 % in M1N1, resulting in N2O reductions of 38.9 % and 30.8 % (OM) and 31.2 % and 21.1 % (M1N1), respectively, and NO reductions of 45.0 % and 34.1 % (OM) and 40.1 % and 28.3 % (M1N1). RDA and correlation analyses showed that the soil organic carbon and ammonium nitrogen content increased while AOB gene abundance and diversity significantly decreased with increasing organic replacement ratio; however, the relative abundance of Nitrosomonas in AOB increased in OM and M1N1, which further demonstrates that AOB are the main driver in vegetable soils. Therefore, the appropriate proportion of organic substitution (OM and M1N1) could decrease the N2O and NO emissions contributed by AOB by affecting the soil physicochemical properties and AOB community structure.
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Betaproteobacteria , Suelo , Suelo/química , Óxido Nítrico , Verduras , Nitrosomonas , Amoníaco/análisis , Carbono , Estiércol , Oxidación-Reducción , Archaea , Fertilizantes/análisis , Microbiología del Suelo , NitrificaciónRESUMEN
High ammonia concentration hinders the efficient treatment of antibiotic production wastewater (APW). Developing effective ammonia oxidation wastewater treatment strategies is an ideal approach for facilitating APW treatment. Compared with traditional nitrification strategies, the partial nitrification process is more eco-friendly, less energy-intensive, and less excess sludge. The primary limiting factor of the partial nitrification process is increasing ammonia-oxidizing bacteria (AOB) while decreasing nitrite-oxidizing bacteria (NOB). In this study, an efficient AOB microbiota (named AF2) was obtained via enrichment of an aerobic activated sludge (AS0) collected from a pharmaceutical wastewater treatment plant. After a 52-day enrichment of AS0 in 250 mL flasks, the microbiota AE1 with 69.18% Nitrosomonas microorganisms was obtained. Subsequent scaled-up cultivation in a 10 L fermenter led to the AF2 microbiota with 59.22% Nitrosomonas. Low concentration of free ammonia (FA, < 42.01 mg L-1) had a negligible effect on the activity of AF2, and the nitrite-nitrogen accumulation rate (NAR) of AF2 was 98% when FA concentration was 42.01 mg L-1. The specific ammonia oxidation rates (SAORs) at 30 °C and 15 °C were 3.64 kg NH4+-N·kg MLVSS-1·d-1 and 1.43 kg NH4+-N·kg MLVSS-1·d-1 (MLVSS: mixed liquor volatile suspended solids). The SAOR was 0.52 kg NH4+-N·kg MLVSS-1·d-1 when the NaCl concentration was increased from 0 to 20 g L-1, showing that AF2 functioning was stable in a high-level salt environment. The ammonia oxidation performance of AF2 was verified by treating abamectin and lincomycin production wastewater. The NARs of AF2 used for abamectin and lincomycin production wastewater treatment were >90% and the SAORs were 2.39 kg NH4+-N·kg MLVSS-1·d-1 and 0.54 kg NH4+-N·kg MLVSS-1·d-1, respectively, which was higher than the traditional biological denitrification process. In summary, AF2 was effective for APW treatment via enhanced ammonia removal efficiency, demonstrating great potential for future industrial wastewater treatment.
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Amoníaco , Microbiota , Aguas Residuales , Aguas del Alcantarillado/microbiología , Nitritos , Antibacterianos , Furilfuramida , Nitrificación , Nitrosomonas , Reactores Biológicos/microbiología , Nitrógeno , Oxidación-Reducción , LincomicinaRESUMEN
A betaproteobacterial chemolithotrophic ammonia-oxidizing bacterium designated APG5T was isolated from supralittoral sand of the Edmonds City Beach, WA, USA. Growth was observed at 10-35 °C (optimum, 30 °C), pH 5-9 (optimum, pH 8) and ammonia concentrations as high as 100 mM (optimum, 1-30 mM NH4Cl). The strain grows optimally in a freshwater medium but tolerates up to 400 mM NaCl. It is most closely related to 'Nitrosomonas ureae' (96.7% 16S rRNA and 92.4% amoA sequence identity). The 3.75-Mbp of AGP5T draft genome contained a single rRNA operon and all necessary tRNA genes and has the lowest G+C content (43.5%) when compared to the previously reported genomes of reference strains in cluster 6 Nitrosomonas. Based on an average nucleotide identity of 82% with its closest relative ('N. ureae' Nm10T) and the suggested species boundary of 95-96%, a new species Nitrosomonas supralitoralis sp. nov. is proposed. The type strain of Nitrosomonas supralitoralis is APG5T (= NCIMB 14870T = ATCC TSD-116T).
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Amoníaco , Arena , ADN Bacteriano/química , ADN Bacteriano/genética , Nitrosomonas/genética , Oxidación-Reducción , Filogenia , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADNRESUMEN
Aerobic ammonia and nitrite oxidation reactions are fundamental biogeochemical reactions contributing to the global nitrogen cycle. Although aerobic nitrite oxidation yields 4.8-folds less Gibbs free energy (∆Gr ) than aerobic ammonia oxidation in the NH4 + -feeding marine recirculating trickling biofilter reactors operated in the present study, nitrite-oxidizing and not ammonia-oxidizing Nitrospira (sublineage IV) outnumbered ammonia-oxidizing Nitrosomonas (relative abundance; 53.8% and 7.59% respectively). CO2 assimilation efficiencies during ammonia or nitrite oxidation were 0.077 µmol-14 CO2 /µmol-NH3 and 0.053-0.054 µmol-14 CO2 /µmol-NO2 - respectively, and the difference between ammonia and nitrite oxidation was much smaller than the difference of ∆Gr . Free-energy efficiency of nitrite oxidation was higher than ammonia oxidation (31%-32% and 13% respectively), and high CO2 assimilation and free-energy efficiencies were a determinant for the dominance of Nitrospira over Nitrosomonas. Washout of Nitrospira and Nitrosomonas from the trickling biofilter reactors was also examined by quantitative PCR assay. Normalized copy numbers of Nitrosomonas amoA were 1.5- to 1.7-folds greater than Nitrospira nxrB and 16S rRNA gene in the reactor effluents. Nitrosomonas was more susceptible for washout than Nitrospira in the trickling biofilter reactors, which was another determinant for the dominance of Nitrospira in the trickling biofilter reactors.
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Nitritos , Nitrosomonas , Amoníaco , Bacterias/genética , Dióxido de Carbono , Nitrosomonas/genética , Oxidación-Reducción , ARN Ribosómico 16S/genéticaRESUMEN
The responses of the operational performance and bacterial community structure of a nitrification membrane bioreactor (MBR) to elevated ammonia loading rate (ALR) were investigated. Effective nitrification performance was achieved at high ALR up to 3.43 kg NH4+-N/m3·d, corresponding to influent NH4+-N concentration of 2000 mg/L. Further increasing influent NH4+-N concentration to 3000 mg/L, the MBR system finally became completely inefficient due to the combined inhibition effect of salinity, free ammonia and free nitrous acid on nitrification. Ammonia-oxidizing bacteria (AOB) Nitrosomonas were enriched with the increase of ALR. The relative abundance of Nitrosomonas in the sludge with ALR of 2.57 kg NH4+-N/m3·d was up to 14.82%, which were 9-fold and 53-fold higher than that in seed sludge and the sludge with ALR of 0.10 kg NH4+-N/m3·d, respectively. The phylogenetic analysis of AOB amoA genes showed that Nitrosomonas europaea/mobilis lineage are chiefly responsible for catalyzing ammonia oxidation at high ALRs.
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Betaproteobacteria , Nitrificación , Amoníaco/química , Bacterias/genética , Reactores Biológicos/microbiología , Nitrosomonas , Ácido Nitroso , Oxidación-Reducción , Filogenia , Salinidad , Aguas del Alcantarillado/químicaRESUMEN
Conventional biological treatment has been reported to be ineffective for pollutant removal in tannery wastewater due to high salinity. To overcome it, this work used salt-tolerant bacteria (STB) isolated from a membrane bioreactor to evaluate the organic and nutrient removal through a series of batch experiments. Compared with the control, the STB reactor enhanced the reduction of persistent organics by 11% based on the double exponential decay model. Besides, the removal of NH4+-N is 26% higher, satisfying the first-order decay model. The nitrification was inhibited entirely in control during 48 h, whilst the assimilation process involved 55% of total nitrogen removal. In the STB reactor, nitrification occurred after 12 h, resulting in significantly increased NO2--N and NO3--N concentrations according to the logistic function. Although nitrification was successfully activated, C/N ratios and free ammonia were identified as limiting factors for STB activity, requiring mitigation strategies in further studies.
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Nitrosomonas , Purificación del Agua , Amoníaco , Reactores Biológicos , Cinética , Nitrificación , Nitritos , Nitrobacter , Nitrógeno , Dinámicas no Lineales , Aguas ResidualesRESUMEN
Partial nitritation (PN) is a bioprocess that is essential for developing cost-effective biological nitrogen removal processes. Understanding the abundant bacterial communities responsible for nitrification under salt stress conditions is important to achieve a stable PN system for treating saline wastewater. Therefore, in this study, we identified the core nitrifying communities and investigated their correlations with the process parameters in a nitrifying bioreactor that was used for treating saline high-strength ammonia wastewater. A PN system worked efficiently under saline conditions with varying operational factors, such as temperature, dissolved oxygen (DO), and alkalinity. Interestingly, the specific oxygen uptake rate (SOUR) became similar under salt-free and saline media after the salt adaption. Next generation sequencing results suggested that the inactivation of Nitrobacter winogradskyi was a key factor for the PN reaction under salt stress conditions. We also found that Nitrosomonas europaea, a freshwater type ammonia-oxidizing bacteria (AOB), was predominantly found under both salt-free and saline conditions, whereas other halotolerant or halophilic AOB species, including Nitrosomonas nitrosa and Nitrosomonas mobilis, became selectively abundant under saline conditions. This implies that adaptation (training of N. europaea) and selection (presence of N. nitrosa and N. mobilis) were simultaneously attributed to selective ammonia conversion for the PN reaction. The redundancy analysis showed that the salinity and ammonia loading rates were statistically significant process parameters that determined the nitrifying bacterial community, suggesting that these parameters drive the adaptation and selection of the core AOB species during the PN reaction. Furthermore, the correlation analysis revealed that the abundance of N. nitrosa and N. mobilis was critically correlated with the specific oxygen uptake rates in saline media containing ammonia.
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Secuenciación de Nucleótidos de Alto Rendimiento , Nitrosomonas , Amoníaco , Reactores Biológicos/microbiología , Nitrificación , Nitritos , Nitrógeno , Oxidación-Reducción , OxígenoRESUMEN
Toxicological batch assays are essential to assess a compound's acute effect on microorganisms. This methodology is frequently employed to evaluate the effect of contaminants in sensitive microbial communities from wastewater treatment plants (WWTPs), such as autotrophic nitrifying populations. However, despite nitrifying batch assays being commonly mentioned in the literature, their experimental design criteria are rarely reported or overlooked. Here, we found that slight deviations in culture preparations and conditions impacted bacterial community performance and could skew assay results. From pre-experimental trials and experience, we determined how mishandling and treatment of cultures could affect nitrification activity. While media and biomass preparations are needed to establish baseline conditions (e.g., biomass washing), we found extensive centrifugation selectively destabilised nitrification activities. Further, it is paramount that the air supply is adjusted to minimise nitrite build-up in the culture and maintain suitable aeration levels without sparging ammonia. DMSO and acetone up to 0.03% (v/v) were suitable organic solvents with minimal impact on nitrification activity. In the nitrification assays with allylthiourea (ATU), dilute cultures exhibited more significant inhibition than concentrated cultures. So there were biomass-related effects; however, these differences minimally impacted the EC50 values. Using different nutrient-media compositions had a minimal effect; however, switching mineral media for the toxicity test from the original cultivation media is not recommended because it reduced the original biomass nitrification capacity. Our results demonstrated that these factors substantially impact the performance of the nitrifying inoculum used in acute bioassays, and consequently, affect the response of AOB-NOB populations during the toxicant exposure. These are not highlighted in operation standards, and unfortunately, they can have significant consequential impacts on the determinations of toxicological endpoints. Moreover, the practical procedures tested here could support other authors in developing testing methodologies, adding quality checks in the experimental framework with minimal waste of time and resources.