Evolution Of Microbial Communities Research Articles

Insights into the Response and Evolution of Microbial Communities During Long-Term Natural Remediation of Contaminated Abandoned Shale Gas Wells

Insights into the Response and Evolution of Microbial Communities During Long-Term Natural Remediation of Contaminated Abandoned Shale Gas Wells

Evolution of microbial community and resistance genes in denitrification system under single and combined exposure to benzethonium chloride and methylparaben

Benzethonium chloride (BZC) and methylparaben (MeP) are commonly added into cosmetics as preservatives, which are frequently detected in wastewater treatment plants. Different response patterns of denitrification system were proposed under single and combined exposure to BZC and MeP (0, 0.5, 5 mg/L) by evaluating system performance, functional genes, extracellular polymeric substance (EPS), cytotoxicity, microbial community structure and resistance genes (RGs). The inhibition effect of BZC on denitrification system was stronger than MeP, and the co-exposure of BZC and MeP showed synergistic effect, enhancing the inhibition effect of BZC single exposure. BZC and/or MeP could promote the diffusion of RGs in sludge, including intracellular RGs (si-RGs) and extracellular RGs (se-RGs). Moreover, the single exposure of BZC and co-exposure of BZC and MeP increased the dissemination risks of RGs in water (w-RGs). IntI1 and tnpA-04, mobile genetic elements (MGEs), correlated positively with diverse RGs from different fractions. Notably, the spread of RGs through horizontal gene transfer mediated by MGEs and the flow of si-RGs into extracellular and water were observed in this study.

Quantifying microbial DNA in metagenomes improves microbial trait estimation

Abstract Shotgun metagenomics is a powerful tool for studying the genomic traits of microbial community members, such as genome size, gene content, etc. While such traits can be used to better understand the ecology and evolution of microbial communities, the accuracy of their estimations can be critically influenced by both known and unknown factors. One factor that can bias trait estimations is the proportion of eukaryotic and viral DNA in a metagenome, as some bioinformatic tools assume that all DNA reads in a metagenome are bacterial or archaeal. Here, we add to a recent debate about the influence of eukaryotic DNA in the estimation of average genome size from a global soil sample dataset using a new bioinformatic tool. Contrary to what was assumed, our reanalysis of this dataset revealed that soil samples can contain a substantial proportion of non-microbial DNA, which severely inflated the original estimates of average genome size. Correcting for this bias significantly improves the statistical support for the negative relationship between average bacterial genome size and soil pH. These results highlight that metagenomes can contain large quantities of non-microbial DNA, and that new methods that correct for this can improve microbial trait estimation.

Characteristics and driving forces of the soil microbial community during 35years of natural restoration in abandoned areas of the Daxin manganese mine, China.

The restoration of mining wastelands, particularly in karst regions contaminated by heavy metals, is an environmental challenge in need of urgent attention. Soil microbes play a vital role in nutrient cycling and ecosystem recovery, yet the long-term evolution of soil microbial communities in such settings remains poorly understood. This study explored the dynamics and influencing factors of soil microbial communities during 35years of natural restoration in abandoned manganese (Mn) mine areas in Guangxi Province, China. The results revealed that the concentrations of Mn, Cd, Zn, and Cu were significantly (p < 0.05) reduced by 80.4-85.3%, 55.3-70.0%, 21.0-38.1%, and 29.4-49.4%, respectively, in the mid-late restoration periods (R19 and R35) compared with R1. The α diversities of the bacterial and fungal communities significantly increased in the middle-late restoration periods (R19 and R35), indicating increased microbial diversity as restoration progressed. The bacterial community structure exhibited more pronounced changes than did the fungal community structure, with significant shifts observed in dominant phyla such as Proteobacteria, Actinobacteria, Acidobacteriota, and Ascomycota. Notably, the relative abundances of Rhizobiales, Burkholderiales, and Hypocreales increased gradually with succession. Co-occurrence network analysis revealed that bacterial interactions became stronger over time, whereas interactions between bacteria and fungi weakened. Mantel tests and partial least squares path modeling (PLS‒PM) identified soil pH, heavy metals (Mn, Cd, Zn, and Cu), and nutrients (SOM and TN) as key drivers shaping the microbial community composition. These factors were more strongly correlated with bacterial communities than with fungal communities, underscoring the different responses of microbial groups to environmental changes during natural restoration. These findings enhance our understanding of the ecological processes governing microbial community succession in heavy metal-contaminated soils undergoing natural restoration.

Case study on the relationship between transmission of antibiotic resistance genes and microbial community under freeze-thaw cycle on cold-region dairy farm

Freeze-thaw cycle (FTC) is a naturally occurring phenomenon in high-latitude terrestrial ecosystems, which may exert influence on distribution and evolution of microbial community in the soil. The relationship between transmission of antibiotic resistance genes (ARGs) and microbial community was investigated upon the case study on the soil of cold-region dairy farm under seasonal FTC. The results demonstrated that 37 ARGs underwent decrease in the abundance of blaTEM from 80.4 % for frozen soil to 71.7 % for thawed soil, and that sul2 from 8.8 % for frozen soil to 6.5 % for thawed soil, respectively. Antibiotic deactivation was identified to be closely related to the highest relative abundance of blaTEM, and the spread of sulfonamide resistance genes (SRGs) occurred mainly via target modification. Firmicutes in frozen soil were responsible for dominating the abundance of ARGs by suppressing the native bacteria under starvation effect in cold regions, and then underwent horizontal gene transfer (HGT) among native bacteria through mobile genetic elements (MGEs). The TRB-C (32.6–49.1 %) and tnpA-06 (0.27–7.5 %) were significantly increased in frozen soil, while Int3 (0.67–10.6 %) and tnpA-04 (11.1–19.4 %) were up-regulated in thawed soil. Moreover, the ARGs in frozen soil primarily underwent HGT through MGEs, i.e. TRB-C and tnpA-06, with increased number of Firmicutes serving as carrier. The case study not only demonstrated relationship between transmission of ARGs and microbial community in the soil under practically relevant FTC condition, but also emphasized the importance for formulating better strategies for preventing FTC-induced ARGs in dairy farm in cold regions.

Unraveling microbial community variation along a salinity gradient and indicative significance to groundwater salinization in the coastal aquifer

Saltwater intrusion poses a global environmental challenge in coastal regions, profoundly influencing groundwater microbial communities and biogeochemical processes. This study aims to elucidate the origin of groundwater salinity and understand the response of microbial interactions to groundwater salination through stable isotopes and 16S rDNA gene sequencing. The findings reveal a significant increase in groundwater TDS from inland to the coastline, ranging from 0.5 g/L to 144.6 g/L. Ionic relationship and isotopic fractionation indicate that the high salinity in groundwater originates not only from paleo–seawater but also from the dissolution of halite. Salty groundwater exhibits lower species richness and diversity than fresh groundwater. TDS, SO42–, and NO2– are the pivotal factors shaping the microbial community of salty groundwater, while NO3– and H2SiO3 are dominant variables influencing fresh groundwater community. This study identifies the order Alteromonadales, family Alteromonadaceae, and genus Marinobacter as potential biomarkers of seawater or paleo–seawater sources. Phylogenetic molecular network analysis of microbial communities illustrates that groundwater salinization results in a more compact microbial network but enhances microbial interactions. Predicted functional genes indicate that sulfate reduction genes (sat, met3, aprA, aprB, dsrA, and dsrB) are more abundant in salty groundwater than in fresh groundwater, suggesting a high metabolic potential for sulfate. These results elucidate the pivotal role of groundwater salinization in microbial community evolution, shaping specific functional zones in coastal groundwater.

Enhanced metabolic entanglement emerges during the evolution of an interkingdom microbial community

While different stages of mutualism can be observed in natural communities, the dynamics and mechanisms underlying the gradual erosion of independence of the initially autonomous organisms are not yet fully understood. In this study, by conducting the laboratory evolution on an engineered microbial community, we reproduce and molecularly track the stepwise progression towards enhanced partner entanglement. We observe that the evolution of the community both strengthens the existing metabolic interactions and leads to the emergence of de novo interdependence between partners for nitrogen metabolism, which is a common feature of natural symbiotic interactions. Selection for enhanced metabolic entanglement during the community evolution repeatedly occurred indirectly, via pleiotropies and trade-offs within cellular regulatory networks, and with no evidence of group selection. The indirect positive selection of metabolic dependencies between microbial community members, which results from the direct selection of other coupled traits in the same regulatory network, may therefore be a common but underappreciated driving force guiding the evolution of natural mutualistic communities.

Swine farm environmental microbiome: exploring microbial ecology and functionality across farms with high and low sanitary status.

Stringent regulations in pig farming, such as antibiotic control and the ban on certain additives and disinfectants, complicate disease control efforts. Despite the evolution of microbial communities inside the house environment, they maintain stability over the years, exhibiting characteristics specific to each type of production and, in some cases, unique to a particular company or farm production type. In addition, some infectious diseases are recurrent in specific farms, while other farms never present these diseases, suggesting a connection between the presence of these microorganisms in animals or their environment. Therefore, the aim of this study was to characterise environmental microbiomes of farms with high and low sanitary status, establishing the relationships between both, health status, environmental microbial ecology and its functionality. For this purpose, 6 pig farms were environmentally sampled. Farms were affiliated with a production company that handle the majority of the pigs slaughtered in Spain. This study investigated the relationship among high health and low health status farms using high throughput 16S rRNA gene sequencing. In addition, to identify ecologically relevant functions and potential pathogens based on the 16S rRNA gene sequences obtained, functional Annotation with PROkaryotic TAXa (FAPROTAX) was performed. This study reveals notable differences in microbial communities between farms with persistent health issues and those with good health outcomes, suggesting a need for protocols tailored to address specific challenges. The variation in microbial populations among farms underscores the need for specific and eco-friendly cleaning and disinfection protocols. These measures are key to enhancing the sustainability of livestock farming, ensuring safer products and boosting competitive edge in the market.

New insight into Na+-promoted microbial electrolysis cell towards hydrogen energy recovery: Feasibility and dual mechanism in salt-containing wastewater treatment

The salt-containing wastewater treatment has become serious challenge, while conductivity and micro-ecosystem disorder severely limited microbial electrolysis cell (MEC) efficiency. In order to synchronously overcome the above bottlenecks, this study proposed an innovative Na+-promoted MEC system for efficient salt-containing wastewater treatment. The Na+ presence greatly improved conductivity to impair electric resistance, resulting in rapid electron transfer pattern towards organic degradation in anode and hydrogen synthesis in cathode. Furthermore, the selective Na+ stress triggered microbial community evolution and improved electroactive bacteria activity after salinity cultivation in MEC (0.09–0.17 mol Na+/L), which played “bacteria screening” role for salt-tolerant “electrochemical hydrogen-producing” bacteria community formation. The organic-degrading and hydrogen-producing bacteria with their assistors were tolerant to Na+ stress, which were considerably enriched into dominant microorganisms, while the unfavorable bacteria responsible for hydrogen consumption and competition were inhibited due to salinity-sensitivity. Correspondingly, the metabolic pathways for metabolism, genetic information processing and environmental information processing were improved, positively associating with organic degradation and hydrogen production. Such dual driving contributions of Na+-improved electron transfer-utilization pattern and Na+-modified microbial metabolisms boosted the organic pollutant degradation at anode to 91.34 % while improving the performance and speeds of hydrogen production by 1.57–1.70 times. The hydrogen abundance was also increased to 71.57 % in biogas. The energy efficiencies relative to external electricity and substrates were elevated by 8.80–28.44 %, the coulombic efficiency raised by 14.05 % and reached 109.72 %, suggesting the positive net energy benefits. The findings provided inspirations to the feasible application of MEC in salt-containing wastewater treatment with efficiency benefits.

A pilot-scale study on the in-situ remediation of acid mine drainage with supplemental of external nutrition: Performance, heavy metal removal and microbial community evolution

Acid mine drainage (AMD), a common environmental problem around the world, is characterized by low pH, high concentrations of heavy metals and sulfate. AMD treatment technology based on stimulating in-situ microorganisms has received widespread attention, but lack of organic matter is a limiting factor that restricts the remediation by heterotrophic microorganisms such as sulfate-reducing bacteria (SRB). In this study, a pilot scale reactor was set up next to an acid reservoir to evaluate the effect of livestock wastes on the in-situ bioremediation of AMD, focusing on performance assessment, heavy metal removal efficacy, and the evolution of the microbial community. Results indicated that the pH of AMD rises rapidly from 3.23 to 4.11, and metals (e.g., Fe, Cu, and Zn) rapidly got removed in Stage I. However, AMD experienced significant stratification in Stage Ⅱ (biogas slurry supplemented). The pH of surface layer (0.5 m below the surface) gradually dropped to 3.67, and the bottom layer (2.3 m below the surface) remained around 4.1, and the metal removal efficiencies further improved. Microbial communities were dominated by Fe-OB and Fe-RB in surface layer, while SRB dominated in bottom layer. The addition of biogas slurry significantly increased the relative abundance of functional microbe in bioremediation. The growth of SRB in the bottom of the reactor made an important contribution to heavy metal removal. Heavy metals were mainly removed through the formation of insoluble hydroxide and sulfide precipitation and co-precipitation. This study innovatively integrates low-cost, locally sourced livestock waste as nutrient supplements into AMD bioremediation processes, and demonstrated the potential for integrating AMD treatment with livestock waste management, addressing both the nutrient needs for AMD processing and the challenge of livestock waste disposal. The findings contribute to the development of cost-effective and eco-friendly strategies for AMD management while advancing the understanding of microbial mechanisms of in-situ bioremediation.

Phollow: Visualizing Gut Bacteriophage Transmission within Microbial Communities and Living Animals.

Bacterial viruses (known as "phages") shape the ecology and evolution of microbial communities, making them promising targets for microbiome engineering. However, knowledge of phage biology is constrained because it remains difficult to study phage transmission dynamics within multi-member communities and living animal hosts. We therefore created "Phollow": a live imaging-based approach for tracking phage replication and spread in situ with single-virion resolution. Combining Phollow with optically transparent zebrafish enabled us to directly visualize phage outbreaks within the vertebrate gut. We observed that virions can be rapidly taken up by intestinal tissues, including by enteroendocrine cells, and quickly disseminate to extraintestinal sites, including the liver and brain. Moreover, antibiotics trigger waves of interbacterial transmission leading to sudden shifts in spatial organization and composition of defined gut communities. Phollow ultimately empowers multiscale investigations connecting phage transmission to transkingdom interactions that have the potential to open new avenues for viral-based microbiome therapies.

Enhancing Rubber Industry Wastewater Treatment through an Integrated AnMBR and A/O MBR System: Performance, Membrane Fouling Analysis, and Microbial Community Evolution.

This study explores the effectiveness of an integrated anaerobic membrane bioreactor (AnMBR) coupled with an anoxic/oxic membrane bioreactor (A/O MBR) for the treatment of natural rubber industry wastewater with high sulfate, ammonia, and complex organic contents. This study was conducted at the lab-scale over a duration of 225 days to thoroughly investigate the efficiency and sustainability of the proposed treatment method. With a hydraulic retention time of 6 days for the total system, COD reductions were over 98%, which reduced the influent from 22,158 ± 2859 mg/L to 118 ± 74 mg/L of the effluent. The system demonstrates average NH3-N, TN, and total phosphorus (TP) removal efficiencies of 72.9 ± 5.7, 72.8 ± 5.6, and 71.3 ± 9.9, respectively. Despite an average whole biological system removal of 50.6%, the anaerobic reactor eliminated 44.9% of the raw WW sulfate. Analyses of membrane fouling revealed that organic fouling was more pronounced in the anaerobic membrane, whereas aerobic membrane fouling displayed varied profiles due to differential microbial and oxidative activities. Key bacterial genera, such as Desulfobacterota in the anaerobic stage and nitrifiers in the aerobic stage, are identified as instrumental in the biological processes. The microbial profile reveals a shift from methanogenesis to sulfide-driven autotrophic denitrification and sulfammox, with evidence of an active denitrification pathway in anaerobic/anoxic conditions. The system showcases its potential for industrial application, underpinning environmental sustainability through improved wastewater management.

Performance and microbial community evolution of toluene degradation in the presence of acetone vapors using hybrid membrane-aerated biofilm reactors (HMABRs)

Biological treatment methodologies offer cost-effective and eco-friendly solutions for volatile organic compounds (VOCs) removal, but they face limitations in effectively treating hydrophobic VOCs. Herein, this study introduces the Hybrid Membrane Aerated Biofilm Reactor (HMABR) for VOC treatment. The HMABR integrates a bio-trickling filter-like spraying function with MABR technology to construct a non-submerge system. What’s more, introducing hydrophilic gases enhances the degradation of hydrophobic VOCs in pollutant biotreatment. While hydrophilic VOCs are readily degraded by microorganisms, the mechanisms of their co-degradation remain understudied. Toluene and acetone, common industrial VOCs, were examined in the HMABR system. HMABR exhibits outstanding toluene removal, reaching a maximum capacity of 142.04 gm−3h−1. The addition of acetone boosts this capacity by 70.1 gm−3h−1, altering EPS composition, and notably increasing the PN/PS ratio from 0.35 to 2.76. It can be inferred that acetone’s presence enhances biofilm EPS hydrophobicity, aiding toluene breakdown. Besides, when adding acetone, the biofilm EPS sample exhibited a more compact secondary protein structure. Analysis of the microbial community in the HMABR system identified a dominance of Pseudomonadota, with an increased abundance of Rhodanobacter, which correlated strongly with toluene degradation in the presence of acetone. Gene analysis revealed an increase in toluene degradation genes in Rhodanobacter when acetone was added. Furthermore, acetone activation was found to enhance metabolic pathways related to xylene degradation and the tricarboxylic acid (TCA) cycle, thereby improving toluene removal efficiency. These findings provide insights into co-metabolism in treating hydrophobic pollutants in HMABR and contribute to designing more effective treatment systems for VOCs.

Denaturing Gradient Gel Electrophoresis Approach for Microbial Shift Analysis in Thermophilic and Mesophilic Anaerobic Digestions.

To determine the evolution of microbial community and microbial shift under anaerobic processes, this study investigates the use of denaturing gradient gel electrophoresis (DGGE). In the DGGE, short- and medium-sized DNA fragments are separated based on their melting characteristics, and this technique is used in this study to understand the dominant bacterial community in mesophilic and thermophilic anaerobic digestion processes. Dairy manure is known for emitting greenhouse gases (GHGs) such as methane, and GHG emissions from manure is a biological process that is largely dependent on the manure conditions, microbial community presence in manure, and their functions. Additional efforts are needed to understand the GHG emissions from manure and develop control strategies to minimize the biological GHG emissions from manure. To study the microbial shift during anaerobic processes responsible for GHG emission, we conducted a series of manure anaerobic digestion experiments, and these experiments were conducted in lab-scale reactors operated under various temperature conditions (28 °C, 36 °C, 44 °C, and 52 °C). We examined the third variable region (V3) of the 16S rRNA gene fingerprints of bacterial presence in anaerobic environment by PCR amplification and DGGE separation. Results showed that bacterial community was affected by the temperature conditions and anaerobic incubation time of manure. The microbial community structure of the original manure changed over time during anaerobic processes, and the community composition changed substantially with the temperature of the anaerobic process. At Day 0, the sequence similarity confirmed that most of the bacteria were similar (>95%) to Acinetobacter sp. (strain: ATCC 31012), a Gram-negative bacteria, regardless of temperature conditions. At day 7, the sequence similarity of DNA fragments of reactors (28 °C) was similar to Acinetobacter sp.; however, the DNA fragments of effluent of reactors at 44 °C and 52 °C were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 97%) and Tepidimicrobium ferriphilum (strain: DSM 16624) (similarity: 100%), respectively. At day 60, the analysis showed that DNA fragments of effluent of 28 °C reactor were similar to Galbibacter mesophilus (strain: NBRC 10162) (similarity: 87%), and DNA fragments of effluent of 36 °C reactors were similar to Syntrophomonas curvata (strain: GB8-1) (similarity: 91%). In reactors with a relatively higher temperature, the DNA fragments of effluent of 44 °C reactor were similar to Dielma fastidiosa (strain: JC13) (similarity: 86%), and the DNA fragments of effluent of 52 °C reactor were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 99%). To authors' knowledge, this is one of the few studies where DGGE-based approach is utilized to study and compare microbial shifts under mesophilic and thermophilic anaerobic digestions of manure simultaneously. While there were challenges in identifying the bands during gradient gel electrophoresis, the joint use of DGGE and sequencing tool can be potentially useful for illustrating and comparing the change in microbial community structure under complex anaerobic processes and functionality of microbes for understanding the consequential GHG emissions from manure.

Ciprofloxacin affects nutrient removal in manganese ore-based constructed wetlands: Adaptive responses of macrophytes and microbes

Ciprofloxacin (CIP) has received considerable attention in recent decades due to its high ecological risk. However, little is known about the potential response of macrophytes and microbes to varying levels of CIP exposure in constructed wetlands. Therefore, lab-scale manganese ore-based tidal flow constructed wetlands (MO-TFCWs) were operated to evaluate the responses of macrophytes and microbes to CIP over the long term. The results indicated that total nitrogen removal improved from 79.93% to 87.06% as CIP rose from 0 to 4 mg L−1. The chlorophyll content and antioxidant enzyme activities in macrophytes were enhanced under CIP exposure, but plant growth was not inhibited. Importantly, CIP exposure caused a marked evolution of the substrate microbial community, with increased microbial diversity, expanded niche breadth and enhanced cooperation among the top 50 genera, compared to the control (no CIP). Co-occurrence network also indicated that microorganisms may be more inclined to co-operate than compete. The abundance of the keystone bacterium (involved in nitrogen transformation) norank_f__A0839 increased from 0.746% to 3.405%. The null model revealed drift processes (83.33%) dominated the community assembly with no CIP and 4 mg L−1 CIP. Functional predictions indicated that microbial carbon metabolism, electron transfer and ATP metabolism activities were enhanced under prolonged CIP exposure, which may contribute to nitrogen removal. This study provides valuable insights that will help achieve stable nitrogen removal from wastewater containing antibiotic in MO-TFCWs.

The fate of plastic wraps in constructed wetland: Surface structure and microbial community

The high use of plastic wraps leads to significant environmental pollution. In this study, the surface structure and microbial community evolution of commercially available plastic wraps [polyethylene (PE), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), and polylactic acid (PLA)] in constructed wetlands (CWs) were investigated. The results indicated that all plastic wraps gradually decreased in molecular weight, crystallinity, melting, and crystallization temperatures, whereas a gradual increase was observed in the surface roughness, polymer dispersity index (PDI), carbonyl index (CI) and Shannon index of microorganisms colonizing the CWs. The aging rate of the plastic wrap was in the order: PLA > PVC > PE > PVDC, at the same site in the CWs, and it was in the order: soil surface > plant roots > subsoil, for the same plastic wrap. The diversity of microorganisms colonizing the same plastic wrap was in the order: plant roots > subsoil > soil surface. The Shannon indices of microorganisms on plastic wraps were lower than those in the soil, indicating that the diversity of microorganisms colonizing plastic wraps is limited. Additionally, the microbial community structure on the plastic surface was co-differentiated by the plastic type, placement position in the CWs, and aging time. Significantly different microbial community structures were found on the PVC and PVDC wrap surfaces, revealing that the chlorine in plastics limits microbial diversity. Unclassified members of Rhizobiaceae and Pseudomonadaceae were the dominant genera on the surface of the plastic wraps, suggesting that they may be the microorganisms involved in plastic degradation processes. The study provides valuable perspectives to facilitate a comprehensive understanding of the migration, fate, and environmental risks associated with microplastics (MPs) in wetlands.

Bio-promoter mediated denitrification recovery from Cd(II) stress: Microbial activity resilience, electron behavior enhancement and microbial community evolution

Denitrification is fragile to toxic substances, while currently there are few regulation strategies for toxic substance-stressed denitrification. This study proposed a combined bio-promoter composed of basic bio-promoter (cytokinin, biotin, L-cysteine, and flavin adenine dinucleotide) and phosphomolybdic acid (PMo12) to recover cadmium(II) (Cd(II)) stressed denitrification. By inhibiting 58.02% and 48.84% of nitrate reductase and nitrite reductase activities, Cd(II) caused all the influent nitrogen to accumulate as NO3–-N and NO2–-N. Combined bio-promoter shortened the recovery time by 21 cycles and improved nitrogen removal efficiency by 10% as the synergistic effect of basic bio-promoter and PMo12. Basic bio-promoter enhanced antioxidant enzyme activities for reactive oxygen species clearance and recovered 23.30% of nicotinamide adenine dinucleotide for sufficient electron donors. Meanwhile, PMo12 recovered electron carriers contents, increasing the electron transfer activity by 60.81% compared with self-recovery. Bio-promoters enhanced the abundance of denitrifiers Seminibacterium and Dechloromonas, which was positively correlated with rapid recovery of denitrification performance.

Influence of Nitrogen Loading on the Performance of Partial Nitrification Processes and the Evolution of Microbial Communities

Stable and efficient partial nitrification reaction and nitrite accumulation are essential for the operation of partial nitrification-anaerobic ammonia oxidation process. This paper investigated the changes in the performance of a partial nitrification bioreactor during the domestication process. After 40 days of domestication, the partial nitrification reaction remained stable, the nitrite accumulation rate (NAR) increased significantly to 85.7%, and the NO2 --N/NH4 +-N ratio stabilized at 1.25 ± 0.04. Both diversity indices (Simpson and Shannon) and richness indices (Ace and Chao1) tend to decrease with domestication. Nitrosomonas as a typical ammonia oxidizing bacterium it increased its relative abundance in the reactor from 0.02 ± 0.007% at P1 to 11.6 ± 2.2% at P2, and at P3 stage the denitrifying functional bacteria norank_f_AKYH76, Dokdonella and unclassified_f_Comamonadaceae reached 33.4 ± 12.5%, 18.8 ± 1.8%, and 10.1 ± 1.3%, respectively, and the increase in the relative abundance of these functional species was also consistent with the accumulation of nitrite nitrogen in the reactor.

Microplastics in anoxic/aerobic membrane bioreactor (A/O-MBR): Characteristics, biofilms, degradation and carrier for antibiotic resistance genes

Wastewater treatment plants (WWTPs)are proposed as one of the ways for microplastics (MPs) to enter the water environment. MPs as the carrier of other pollutants, the inevitable aging process will change the characteristics and fate of MPs. Herein, the physicochemical property alteration, microbial community evolution and antibiotic resistance genes (ARGs) occurrence of the aged MPs surface were analyzed in A/O-MBR system. Remarkable alteration in MPs surface properties, which included the decrease in hydrophobicity and the increase in oxygen-containing functional groups, led to aging of MPs. Aging MPs are more likely to grow biofilms, which further increased the probability of microbial colonization. The genera Hydrogenophaga, Exiguobacterium, Enterobacter, Vibrio, Flavobacterium and Bacillus on MPs surface showed higher degradation potential. ARGs determination results indicated that MPs could enrich ARGs on their surface, and the relative abundance of β-lactam ARGs on different MPs surfaces was the highest. The above research results indicated that MPs in sewage treatment systems not only undergo aging, but also carry ARGs, causing further harm to the environment.

Evolution of microbial community and the volatilome of fresh-cut chili pepper during storage under different temperature conditions: Correlation of microbiota and volatile organic compounds

The effect of temperature conditions on the evolution of microbial communities and volatile organic compounds (VOCs) in fresh-cut chili peppers during storage was investigated. Results showed that Proteobacteria and Actinobacteriota were the dominant phyla in fresh-cut chili peppers. During storage, bacterial communities changed more dramatically than fungi. Different temperature conditions significantly affected the shift of bacteria at the genus level. At the beginning of storage, Rhodococcus, Pantoea, and Pseudomonas dominated the bacteria. However, on day 8, Pantoea and Enterobacter became the predominant genera at 5 °C and high temperatures (10, 15 °C, dynamic temperature), respectively. No significant variability in bacterial species was observed between different batches. Additionally, 140 VOCs were determined in fresh-cut chili peppers. Twenty-two VOCs were screened and could be recommended as potential spoilage markers. Based on Spearman's correlation analysis results, Enterobacter and Enterococcus were the most positive microorganisms correlated with spoilage markers.