Oxidation Bacteria Research Articles

Community composition and abundance of complete ammonia oxidation (comammox) bacteria in the Lancang River cascade reservoir

The construction of the reservoir has changed the nitrogen migration and transformation processes in the river, and a large amount of sediment deposition in the reservoir may also lead to the spatial differentiation of complete ammonia oxidation (comammox) bacteria. The study investigated the abundance and diversity of comammox bacteria in the sediments of three cascade reservoirs, namely, Xiaowan, Manwan, and Nuozhadu on the Lancang River in China. In these reservoirs, the average amoA gene abundance of clade A and clade B of comammox bacteria, ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) was 4.16 ± 0.85 × 105, 1.15 ± 0.33 × 105, 7.39 ± 2.31 × 104, and 3.28 ± 0.99 × 105 copies g−1, respectively. The abundance of clade A was higher than that of other ammonia oxidizing microorganisms. The spatial variation of comammox bacteria abundance differed among different reservoirs, but the spatial variation trends of the two clades of comammox bacteria in the same reservoir were similar. At each sampling point, clade A1, clade A2, and clade B coexisted, and clade A2 was usually the dominant species. The connection between comammox bacteria in the pre-dam sediments was looser than that in non-pre-dam sediments, and comammox bacteria in pre-dam sediments exhibited a simpler network structure. The main factor affecting comammox bacteria abundance was NH4+-N, while altitude, temperature, and conductivity of overlying water were the main factors affecting comammox bacteria diversity. Environmental changes caused by differences in the spatial distribution of these cascade reservoirs may be the main driver of the changes of community composition and abundance of comammox bacteria. This study confirms that the construction of cascade reservoirs results in niche spatial differentiation of comammox bacteria.

Effect of Anammox Granular Sludge Type on the CANON Process with Immobilized Fillers Treating Domestic Wastewater

Immobilized fillers were prepared using intact and crushed ammonia oxidation granular sludge (AnGS) to compare their effects on the completely autotrophic N-removal over nitrite (CANON) process in domestic sewage. Using pre-aerated domestic sewage as an influent, the effect of granular type on nitrogen removal was investigated under intermittent aeration. The results show that the total nitrogen removal (TNR) of the crushed AnGS immobilized filler was 75.8–80.0% at a dissolved oxygen (DO) concentration of 3 mg/L, while the intact AnGS immobilized filler required a DO of 4 mg/L to achieve the same TNR level. The DO concentration is the key factor affecting the nitrogen removal efficiency, because partial nitrification was affected by the DO concentration. Candidatus Kuenenia was the dominant genus of anaerobic ammonium oxidation (anammox) bacteria, and its relative abundance was higher in the crushed AnGS immobilized filler (21.11%) than in the intact AnGS immobilized filler (9.60%). Furthermore, the immobilized filler could inhibit the growth of nitrite-oxidizing bacteria (NOB), and the relative abundance of Nitrospira, the major NOB genus, decreased after operation. The results of this study indicate that the use of AnGS immobilized filler is a promising strategy to strengthen the CANON process in municipal wastewater treatment.

Design strategy and mechanism of nitrite oxidation suppression of elevated loading rate partial nitritation system.

There is a current need for a low operational intensity, effective and small footprint system to achieve stable partial nitritation for subsequent anammox treatment at mainstream municipal wastewaters. This research identifies a unique design strategy using an elevated total ammonia nitrogen (TAN) surface area loading rate (SALR) of 5 g TAN/m2.d to achieve cost-effective, stable, and elevated rates of partial nitritation in a moving bed biofilm reactor (MBBR) system under mainstream conditions. The elevated loaded partial nitritation MBBR system achieves a TAN surface area removal rate (SARR) of 2.01 ± 0.07 g TAN/m2.d and NO2 --N: NH4 +-N stoichiometric ratio of 1.15:1, which is appropriate for downstream anammox treatment. The elevated TAN SALR design strategy promotes nitrite-oxidizing bacteria (NOB) activity suppression rather than a reduction in NOB population as the reason for the suppression of nitrite oxidation in the mainstream elevated loaded partial nitritation MBBR system. NOB activity is limited at an elevated TAN SALR likely due to thick biofilm embedding the NOB population and competition for dissolved oxygen (DO) with ammonia-oxidizing bacteria for TAN oxidation to nitrite within the biofilm structure, which ultimately limits the uptake of DO by NOB in the system. Therefore, this design strategy offers a cost-effective and efficient alternative for mainstream partial nitritation MBBR systems at water resource recovery facilities.

Ubiquitous occurrence and functional dominance of comammox Nitrospira in full-scale wastewater treatment plants

The recent discovery of complete ammonia oxidation (comammox) bacteria has fundamentally upended the traditional two-step nitrification conception, but their functional importance in wastewater treatment plants (WWTPs) is still poorly understood. This study investigated distributions of comammox Nitrospira, ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in activated sludge samples collected from 25 full-scale WWTPs. Using quantitative PCR (qPCR) and 16S rRNA gene amplicon sequencing, our results revealed that comammox Nitrospira ubiquitously occurred in all of 25 WWTPs and even outnumbered AOB and AOA with an average abundance of 1∼183 orders of magnitude higher in 19 WWTPs. Moreover, DNA-based stable isotope probing (DNA-SIP) assays validated that comammox Nitrospira actively participated in ammonia oxidation in the three microcosms seeding with activated sludge from three typical WWTPs, in which the ratios of comammox amoA to AOB amoA were at the range of 1∼10, 10∼100 and >100, respectively. Phylogenetic analysis in heavy fractions further indicated that Nitrospira nitrosa (N. nitrosa) was the dominant and active species. We quantified the contribution of ammonia oxidizers based on the currently available kinetic parameters of the representative species and found that comammox made major contributions to ammonia oxidation than other nitrifiers (5 ∼ 106 times that of AOB). The findings not only demonstrate the ubiquitous occurrence of comammox, but also highlight their functional dominance in ammonia oxidation in WWTPs.

Performance and microbial analysis of a fluidized bed membrane bioreactor operated in the partial nitrification and anammox (PN/A) mode for polishing anaerobically treated effluent to industrial discharge standard

This study evaluates the performance and microbial dynamics of an ORP-controlled fluidized bed membrane bioreactor impregnated with partial nitrification and anammox culture (FMBRPN/A) for polishing the low COD/NH4+ anaerobically treated effluent of the seafood processing industry. Results showed that the highest average removal of COD and total nitrogen were 68.6% and 75.0% at COD/NH4+ 0.44 and 0.33, respectively. Heterotrophic denitrification accounted for only 3.0–7.1% of the overall nitrogen removals at COD/NH4+ 0.33–0.55. A low nitrite oxidation rate observed indicated that almost all NO3- came from anammox reactions. Data on ammonia oxidation rate, nitrite oxidation rate, and anammox nitrogen removal rate pointed to the competitive advantage between heterotrophic and nitrifying/anammox consortia at higher and lower COD/NH4+ ratios. When salinity threat at 5 g/L NaCl in the influent was imposed to FMBRPN/A, nitrogen removal was almost completely eliminated but quickly recovered to 25.5% as organic removal was not affected. Activities of the nitrogenous autotrophic organisms and heterotrophic microbes were strongly dependent on the presence of organic and salinity in the wastewater. Microbial analysis of biofilm formed on the membrane surface showed a significant difference in the succession of dominant bacteria during the experiments. Next Generation Sequencing indicated the dynamic shifting proportions of ammonium oxidizing bacteria (AOB), nitrite oxidization bacteria (NOB), denitrifying bacteria (DNB), and anammox bacteria (AMX) ranging from 49.4% to 64.2% at various COD/NH4+ ratios, which suggested their syntrophic relationship. Superior membrane retention of FMBRPN/A for heterotrophic and slow-growing autotrophic cells facilitated system stability and efficiency to meet the industrial effluent standard.

Microbial mixotrophic denitrification using iron(II) as an assisted electron donor

Mixotrophic denitrification processes have a great potential in nitrogen removal in biological wastewater treatment processes. However, so far, few studies have focused on the mixotrophic denitrification system using Fe(II) as an exclusively assisted electron donors and the underlying mechanisms in such a process remain unclear. Furthermore, the mechanisms by which microorganisms cover carbon, nitrogen, phosphorus and iron in an iron-assisted mixotrophic system remain unrevealed. In this work, we explore the feasibility of using Fe(II) as an assisted electron donor for enhancing simultaneous nitrogen and phosphorus removal via long-term reactor operation and batch tests. The results show that Fe(II) could provide electrons for efficient nitrate reduction and that biological reactions played a predominant role in these systems. In these systems Thermomonas, a strain of nitrate-reduction Fe(II)-oxidation bacterium, was enriched and accounted for a maximum abundance of 60.2%. These findings indicate a great potential of the Fe(II)-assisted mixotrophic denitrification system for practical use as an efficient simultaneous nitrogen and phosphorus removal process.

Stepwise conversion of methane to methanol on Cu and Fe/zeolites prepared in solid state: the effect of zeolite type and activation temperature

AbstractBACKGROUNDGrand efforts have been recently devoted to the development of catalysts based on the excellent performance of Cu‐ and Fe‐dependent enzymes in methanotrophic bacteria for the partial oxidation of methane to methanol under ambient conditions. As a continuation of the study on the stepwise manner for this conversion over zeolite‐based catalysts, in this work, the effects of zeolite topology and activation temperature on the catalytic performance of Cu‐ and Fe‐containing zeolites were investigated.RESULTSCu species exchanged in the medium‐pore zeolites (mordenite, ZSM‐5, and ferrierite) afforded better methanol production, while large‐pore zeolites (zeolite β and zeolite γ) were inappropriate to accommodate active Cu sites. Notably, Cu/silicalite‐1 containing CuO species was also reactive to methane after the activation in O2, yielding a minor methanol amount. Furthermore, the activity of Fe/mordenite towards the methanol in the O2‐assisted procedure was reported for the first time but with a much lower yield as compared to that of Cu/mordenite. The methanol yield over Cu/mordenite increased with the activation temperature because increasing the activation temperature favored the Cu‐exchange degree with a higher priority at the side pockets as compared to the main channels of mordenite, as evidenced from infrared analysis.CONCLUSIONThe selective oxidation of methane to methanol by O2 via a stepwise manner can be obtained over both ion‐exchanged Cu species and well‐dispersed CuO nanoparticles with better activity being recorded for the former. The activity of Cu‐exchanged zeolites was considerably dependent on the zeolite topology and the charge‐balancing position of the Cu2+ cations. © 2023 Society of Chemical Industry (SCI).

Mitigating mechanism of nZVI-C on the inhibition of anammox consortia under long-term tetracycline hydrochloride stress: Extracellular polymeric substance properties and microbial community evolution

In this study, activated carbon-loaded nano-zero-valent iron (nZVI-C) composites were added to anaerobic ammonium oxidation bacteria (AnAOB) to overcome the inhibition of tetracycline hydrochloride (TCH). Results showed that 500 mg L−1 nZVI-C effectively mitigated the long-term inhibition of 1.5 mg L−1 TCH on AnAOB and significantly improved the total nitrogen removal efficiency (TNRE) (from 65.27% to 86.99%). Spectroscopic analysis revealed that nZVI-C increased the content of N–H and CO groups in EPS, which contributed to the adsorption of TCH. The accumulation of humic acid-like substances in EPS was also conducive to strengthening the extracellular defense level. In addition, TCH-degrading bacteria (Clostridium and Mycobacterium) were enriched in situ, and the abundance of Ca. Brocadia was significantly increased (from 10.69% to 18.59%). Furthermore, nZVI-C increased the abundance of genes encoding tetracycline inactivation (tetX), promoted mineralization of TCH by 90%, weakening the inhibition of TCH on microbial nitrogen metabolism. nZVI-C accelerated the electron consumption of anammox bacteria by upregulating the abundance of electron generation genes (nxrA, hdh) and providing electrons directly.

Mainstream wastewater treatment by polyaluminium ferric chloride (PAFC) flocculation and nitritation-denitritation membrane aerated biofilm reactor (MABR)

To reduce the carbon emission of sewage treatment, a novel adsorption-biodegradation (A-B) process, flocculation pretreatment as A-stage and nitritation-denitritation MABR as B-stage, was proposed in the study. It was found that 27.37 %–49.69 % of organics can be removed from actual wastewater by flocculation with polyaluminium ferric chloride (PAFC). The pretreated wastewater could be further treated by nitritation-denitritation MABR with low aeration pressure (2–5 kPa) without any extra organics. The NH4+-N, total nitrogen (TN), and chemical oxygen demand (COD) removal efficiency can reach 100 %, 84.04 %, and 98.54 %, respectively. It was also found that the relative abundances of ammonia-oxidizing bacteria (AOB) (3.81 %–4.76 %) and denitrifying bacteria (DB) (4.30 %–5.59 %) were higher than that of nitrite-oxidizing bacteria (NOB) (2.08 %–2.39 %) in the MABR even after 130 days of operation according to the microorganism identification by 16S rRNA sequencing technology. This implied that low oxygen aeration in MABR can prevent NOB from becoming dominant bacteria. Furthermore, it was found that there were indeed traces of anaerobic ammonia oxidation (Anammox) bacteria (0.04 %–0.08 %) and were closely surrounded by other microorganisms in the MABR based on fluorescence in situ hybridization (FISH) technology. In addition, the microbial nitrogen metabolism process in the MABR was further analyzed according to the Kyoto Encyclopedia of Genes and Genomes (KEGG). The promising mainstream A-B process proposed in this study was expected to achieve nitrogen removal with little carbon and energy consumption in wastewater treatment plants (WWTPs).

Shifts in intestinal microbiota and improvement of sheep immune response to resist Salmonella infection using Toll-like receptor 4 (TLR4) overexpression.

Toll-like receptor 4 (TLR4) identifies Gram-negative bacteria or their products and plays a crucial role in host defense against invading pathogens. In the intestine, TLR4 recognizes bacterial ligands and interacts with the immune system. Although TLR4 signaling is a vital component of the innate immune system, the influence of TLR4 overexpression on innate immune response and its impact on the composition of the intestinal microbiota is unknown. Here, we obtained macrophages from sheep peripheral blood to examine phagocytosis and clearance of Salmonella Typhimurium (S. Typhimurium) in macrophages. Meanwhile, we characterized the complex microbiota inhabiting the stools of TLR4 transgenic (TG) sheep and wild-type (WT) sheep using 16S ribosomal RNA (rRNA) deep sequencing. The results showed that TLR4 overexpression promoted the secretion of more early cytokines by activating downstream signaling pathways after stimulation by S. Typhimurium. Furthermore, diversity analysis demonstrated TLR4 overexpression increased microbial community diversity and regulated the composition of intestinal microbiota. More importantly, TLR4 overexpression adjusted the gut microbiota composition and maintained intestinal health by reducing the ratio of Firmicutes/Bacteroidetes and inflammation and oxidative stress-producing bacteria (Ruminococcaceae, Christensenellaceae) and upregulating the abundance of Bacteroidetes population and short-chain fatty acid (SCFA)-producing bacteria, including Prevotellaceae. These dominant bacterial genera changed by TLR4 overexpression revealed a close correlation with the metabolic pathways of TG sheep. Taken together, our findings suggested that TLR4 overexpression can counteract S. Typhimurium invasion as well as resist intestinal inflammation in sheep by regulating intestinal microbiota composition and enhancing anti-inflammatory metabolites.

Arsenic Detoxification by As(III)-Oxidizing Bacteria: A Proposition for Sustainable Environmental Management

Arsenic Detoxification by As(III)-Oxidizing Bacteria: A Proposition for Sustainable Environmental Management

The short and long-term effect of polystyrene nanoplastics on nitrifying sludge at high nitrite concentrations

The effect of nanoplastics (NPs) on nitrite oxidation bacteria (NOB) community in treating high-strength wastewater remains unclear, which seriously affects the stability of nitrogen removal process. In this study, highly active nitrifying sludge was enriched and exposed to 50 nm polystyrene NPs (PS-NPs) for short-term (1, 100, 500, and 1000 mg/L, 1.5 hr) and long-term (1, 10, 100 mg/L, 40 days) at high nitrite concentration. In contrast to previous studies, our results showed that the exposures to PS-NPs had little effect on nitrifying performances. After long-term exposure, the protein/polysaccharide ratios in extracellular polymeric substances (EPS) were positively correlated with PS-NPs concentrations (0.78–0.99). The produced reactive oxygen species (ROS) were gradually removed, and PS-NPs higher than 10 mg/L caused damage to membrane integrity. Long-term exposure for 40 days increased the community diversity and caused significant differences between the control and exposed communities. The control group were dominated by Nitrobacter and Exiguobacterium, while the exposure group was dominated by Bacillus, Mycobacterium, and Nitrospira. A noticeable shift in the NOB community from Nitrobacter (26.5% to 3.4%) to Nitrospira (1.61% to 14.27%) was observed. A KEGG analysis indicated a decrease in cell growth and death, cell motility and energy metabolism. It appeared that NOB could adapt to PS-NPs stress through enhanced secretion and removal of oxidative damage. Overall, this study provided new insights into the response mechanism of NOB to PS-NPs exposure.

Reactive and microbial inhibitory mechanisms depicting the panoramic view of pH stress effect on common biological nitrification

pH is a crucial factor of microbial nitrification, which often combines with high-strength ammonium to influence nitrogen removal pathway in wastewater treatment. However, the detailed inhibitory mechanisms of pH stress are not sufficiently disclosed yet. In this study, the pH stress effect on nitrification was comprehensively studied by a set of experiments which identified the reactivity of nitrification processes and activity of nitrifiers, the time dependence of inhibition effect and the hybrid pH stress effect with ammonium. The results revealed two distinct inhibitory mechanisms dominating in alkaline and acid ranges. In alkaline range (pH > 8), pH stress causes physiological damages on microorganisms which is named as microbial inhibition. It has the features of less recoverability of nitrifiers, time-dependent inhibition effect and low pH-tolerance of nitrite oxidation bacteria. Free ammonia enhanced microbial inhibition and greatly promoted nitrite accumulation. A novel reactive inhibition mechanism dominated in acid range (pH < 7) was disclosed. It only impedes ammonia oxidation process (AOP) but not impair microbial activity obviously and the effect is time-independent. The mechanism was clarified from H+ transport because AOP involved H+ production. The H+ transport was impeded under acid stress owing to the decrease of pH gradient across cell membrane. The two mechanisms formed a panoramic view of pH stress effect on nitrification advancing the understanding of nitrifier adaptability and nitritation regulation in wastewater treatment processes.

Starting-up performances and microbial community shifts in the coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) and anammox treating nitrate and ammonium contained wastewater

A novel coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) (NO3−-N→NO2−-N) and anaerobic ammonium oxidation (Anammox) was developed using anaerobic sequencing batch reactor (ASBR) in this work. The integrated process comprised two stages. Firstly, the starting-up of SAPD process succeeded by gradually increasing the influent nitrate and sulfide in 95 days. The average nitrate removal efficiency (NRE) and NO2−-N accumulation rates were 71.24% ± 0.21% and 46.44% ± 0.53% at SAPD process (days 75–95). Then, successful coupling process (SAPD-A) was implemented in two stages (stage I and stage II of SAPD-A). In stage I, it is feasible to promote the successful construction of SAPD-A process by elevating influent ammonium only based on SAPD system, making the NRE increased from 44.45% ± 0.46% (day 95) to 64.62% ± 0.12% at the end of stage I in SAPD-A system (day 126). Meanwhile, the ammonium nitrogen removal efficiency (ARE) and total nitrogen removal efficiency (TN-RE) also rose up to 42.46% ± 2.02% and 63.28% ± 0.54% respectively. Furthermore, the average ARE, NRE and TN-RE during the stage II in the bioreactor could reach 65.17% ± 1.45%, 74.50% ± 0.81% and 77.81% ± 0.37% by loading some biofilters (with of approximate 10% of the volume of the bioreactor) attached anaerobic ammonium oxidation bacteria (AnAOB). High-throughput sequencing results showed that the dominant genera concerning nitrogen removal were norank_f_norank_o_Fimbriimonadates (with the abundance of 2.88–8.54%), norank_ o_ norank _ c_ OM190 (2.48–4.41%), norank_f_norank_o_norank_c_WWE3 (11.01–17.69%), subgroup_10 (1.97–3.81%), Limnobacter（2.17–3.49%）, norank_f_n orank_ o_norank_ c_OLB14 (2.03–5.23%), norank-f-PHOS-HE36 (2.18–5.5%), Ellin6067 (1.34–2.24%) and Candidatus_ Brocadia (1.95–2.42%) during the whole starting-up period of coupling SAPD-A process. Batch experiments revealed that the sulfide was fully oxidized within 2 h, with the maximum reaction rate of 38.30 ± 1.53 mg (L h)−1 in the first 1 h. Simultaneously, the concentration of nitrate sharply decreased from 53.08 ± 0.23 mg L−1 to 24.16 ± 0.42 mg L−1 with the reaction rate of 66.41 ± 2.12 mg (L h)−1 in 0.5 h. Also, the ammonium concentration significantly declined from 47.88 ± 0.34 mg L−1 to 10.98 ± 0.39 mg L−1 in 8 h. Anammox process was responsible for the dominant nitrogen removal in the coupling SAPD-A system.

Green synthesis of silver nanoparticles using Helianthemum lippii extracts (Hl-NPs): Characterization, antioxidant and antibacterial activities, and study of interaction with DNA

This study's objective was to formulate silver nanoparticles by reducing the extraction of Helianthemum lippii. We looked into how AgNPs attach to deoxyribonucleic acid using cyclic voltammetry and spectroscopy (UV-Vis) techniques. The DPPH, Reduction Power (RP), and -Carotene Bleaching (BCB) tests have also been used to assess antioxidant activity. The effectiveness of AgNPs against six bacterial strains was also tested. Biosynthesized AgNPs were characterized using UV-Visible and FTIR Spectroscopy, powder-XRD, and EDX technics. The UV-vis spectra at 428 nm validated the outcomes of the synthesized AgNPs. The results of SEM, EDX and powder-XRD, examination showed that AgNPs were the crystallite cubic, high purity with size ranged from 4.81 to 12.84 nm. Additionally, the produced AgNPs' FTIR spectra revealed the presence of phytoconstituents that served as capping agents. Also, the experimental findings showed that AgNPs had a strong propensity for binding to DNA through electrostatic interactions, which is supported by binding energy values. Additionally, it was demonstrated that biosynthesized AgNPs had high antioxidant activity (IC50 values for the DPPH, RP, and BCB assays were 3.16 ± 0.02µg/mL,1.73 ± 0.01µg/mL, and 1.99 ± 0.04, respectively). Additionally, results indicated an efficient antibacterial action of AgNPs with the MIC range from 0.04 to 0.18 mg/mL against six bacterial strains. To conclude, the current study opens avenues that make them candidates for therapy against many cancer disorders. Additionally, they may be used as treatment for other illnesses brought on by oxidative stress and bacteria.

Conductive carrier promotes synchronous biofilm formation and granulation of anammox bacteria

The extracellular electron transfer capability of some anaerobic ammonium oxidation (anammox) bacteria was confirmed in recent years. However, the effect of conductive carriers on the synchronous formation of anammox biofilm and granules is rarely reported. Anammox biofilm and granules with compact and stable structures accelerate the initiation and enhance the stability of the anammox process. In this study, we found that the conductive carbon fiber brush (CB) carrier promoted synchronous biofilm formation and granulation of anammox bacteria in the internal circulation immobilized blanket (ICIB) reactor. Compared with polyurethane sponge and zeolite carrier, the ICIB reactor packed with CB carrier can be operated under the highest total nitrogen loading rate of 6.53 kg-N/(m3·d) and maintain the effluents NH4+-N and NO2−-N at less than 1 mM. The volatile suspended solids concentration in the ICIB reactor packed with conductive carrier increased from 5.17 ± 0.40 g/L of inoculum sludge to 24.24 ± 1.20 g/L of biofilm, and the average particle size of granules increased from 222.09 µm to 879.80 µm in 150 days. Fluorescence in situ hybridization analysis showed that anammox bacteria prevailed in the biofilm and granules. The analysis of extracellular polymeric substances indicated that protein and humic acid-like substances played an important role in the formation of anammox biofilm and granules. Microbiome analysis showed that the relative abundance of Candidatus Jettenia was increased from 0.18% to 38.15% in the biofilm from CB carrier during start-up stage. This study provides a strategy for rapid anammox biofilm and granules enrichment and carrier selection of anammox process.

Isolation and Characterization of A Novel Iron–Sulfur Oxidizing Bacterium Acidithiobacillus Ferrooxidans YQ-N3 and its Applicability in Coal Biodesulfurization

Acidithiobacillus ferrooxidans is a chemotrophic, aerobic, acidophilic, and Gram-negative bacterium that plays a key role in iron and sulfur cycling and has a wide range of applications in the industrial field. A novel A. ferrooxidans strain, hereinafter referred to as strain “YQ-N3”, was isolated from sediments of a river polluted by acid mine drainage (AMD) of an abandoned mine in Shanxi, China. The whole genome sequencing results revealed that A. ferrooxidans YQ-N3 has a 3,217,720 bp genome, which is comprised of one circular chromosome and five circular plasmids (Plasmid A, Plasmid B, Plasmid C, Plasmid D, Plasmid E). Plasmid E, a new plasmid, had not been annotated in the reference database. A. ferrooxidans YQ-N3 had a close evolutionary relationship with A. ferrooxidans ATCC23270 and A. ferridurans JCM18981 and exhibited higher similarity in its genomic structure with A. ferrooxidans ATCC23270. Multiple genes related to environmental resistance and iron and sulfur metabolism were predicted from its genome. A. ferrooxidans YQ-N3 can remarkably increase the oxidation rate of Fe2+ and S0 and enhance the hydrophilicity of S0, which was supported by functional gene analysis and laboratory experiments. The biological desulfurization experiment demonstrated that A. ferrooxidans YQ-N3 can reduce the sulfur content in coal by removing pyrite sulfur and organic sulfur.

Unveiling the effects of soluble starch, ethanol, and sodium acetate on the interactions of functional microorganisms and nitrogen removal in a partial nitritation and anammox biofilm system

Different organic matters have different effects on the nitrogen removal performance of partial nitritation and anammox (PN/A) biofilm system. In this study, the effects of adding soluble starch, ethanol, and sodium acetate on the functional microorganisms and nitrogen removal in the PN/A biofilm system are investigated. The results show that ethanol had the strongest effects on the ammonium-oxidizing bacteria (AOB) growth, enrichment, and ammonium nitrogen removal rate, followed by soluble starch and sodium acetate. However, the suppression of anaerobic ammonium oxidation bacteria (AnAOB) and decrease in total nitrogen removal rate were affected the most by ethanol, followed by soluble starch and sodium acetate. In addition, the enrichment of nitrifying oxidizing bacteria (NOB) was the most strongly influenced by ethanol, followed by soluble starch and sodium acetate. Furthermore, the enrichment of phylum Proteobacteria was facilitated by ethanol > soluble starch > sodium acetate. The enrichment of phylum Nitrospirae and genus Nitrospira were influenced by ethanol > soluble starch > sodium acetate. However, the suppression of the phylum Planctomycetes and the genus Candidatus Brocadia were affected by ethanol > soluble starch > sodium acetate. These results show that the PN/A biofilm system is suitable for the treatment of ammonium nitrogen wastewaters containing organic salt (sodium acetate) but not for treating wastewaters containing organic alcohol (ethanol) and macromolecular organic matter (soluble starch).

Alleviating acid inhibition via bentonite supplementation during acidulated swine manure anaerobic digestion: Performance enhancement and microbial mechanism analysis

Swine manure is usually transmitted by the “collection-storage-transport” mode of the biogas project. However, this particular application pattern results in high volatile fatty acids (VFAs) concentration due to the long transition time in the “collection-storage-transport” process. In this work, acidulated swine manure anaerobic digestion (AD) with bentonite supplementation was firstly investigated with an expectation of acid alleviation, performance enhancement and microbial mechanism. Results indicated that the methane production rate in the 20 g/L bentonite-added digester was 2.87 fold higher than that of the control digester. Chemical oxygen demand (COD) removal rate was elevated by 140.1% via bentonite supplementation. Besides, the rapid decrease of VFAs and ammonia indicated that bentonite supplementation could offer buffering capacity and alleviate acid inhibition. Microbial community analysis revealed that acetoclastic methanogenesis (Methanosaeta and Methanosarcina) was the predominant methanogenesis pathway in this AD system. Syntrophic acetate oxidation (SAO) bacteria were discovered in the bentonite-added digester, and they converted acetate into H2/CO2 to support hydrogenotrophic methanogenesis. This study could offer guidance for acidulated swine manure AD in the practical biogas project.

Abundance, diversity and changes to environmental variables of comammox Nitrospira in bioretention system

The nitrogen removal of bioretention system (BRS) mainly depends on various microorganisms, among which complete ammonia oxidization bacteria (comammox) are important nitrogen removers. However, the abundance and diversity of comammox Nitrospira in BRS have been rarely studied, and its role in ammonia oxidation is unknown. In this study, 18 field BRSs were investigated to distinguish the abundance and diversity of comammox Nitrospira followed by a mesocosm bioretention experiment to examine the variation in the abundance of comammox Nitrospira after rainfall event. The results showed that: (1) comammox Nitrospira amoA functional genes were widely distributed in the field BRSs with the absolute abundance of 4.72 × 102 to 9.97 × 103 copies∙g−1 dry soil; (2) within 12–24 h after rainfall event, comammox Nitrospira increased rapidly, and its growth rate was even higher than that of ammonia oxidizing bacteria (AOB); (3) a total of 20 operational taxonomic units (OTUs) of comammox Nitrospira amoA genes were detected in the field BRSs. These OTUs were classified as Nitrospira inopinata, Ca. Nitrospira nitrificans, and comammox Nitrospira clade A.2.1 on phylogeny. Except one unique OTU, the other OTUs were phylogenetically similar to the sequences detected in wetlands; (4) different OTUs responded differently to soil physicochemical factors, indicating the environmental adaptability of comammox Nitrospira. These results were helpful to improve the understanding of microbial nitrogen transformation pathways and their roles in BRS.