Microbial Community Succession Research Articles

Metal availability shapes early life microbial ecology and community succession.

The gut microbiota plays a critical role in human health and disease. Microbial community assembly and succession early in life are influenced by numerous factors. In turn, assembly of this microbial community is known to influence the host, including immune system development, and has been linked to outcomes later in life. To date, the role of host-mediated nutritional immunity and metal availability in shaping microbial community assembly and succession early in life has not been explored in depth. Using a human infant cohort, we show that the metal-chelating protein calprotectin is highly abundant in infants. Taxa previously shown to be successful early colonizers of the infant gut, such as Enterococcus, Enterobacteriaceae, and Bacteroides, are highly resistant to experimental metal starvation in culture. Lactobacillus, meanwhile, is highly susceptible to metal restriction, pointing to a possible mechanism by which host-mediated metal limitation shapes the fitness of early colonizing taxa in the infant gut. We further demonstrate that formula-fed infants harbor markedly higher levels of metals in their gastrointestinal tract compared to breastfed infants. Formula-fed infants with high levels of metals harbor distinct microbial communities compared to breastfed infants, with higher levels of Enterococcus, Enterobacter, and Klebsiella, taxa which show increased resistance to the toxic effects of high metal concentrations. These data highlight a new paradigm in microbial community assembly and suggest an unappreciated role for nutritional immunity and dietary metals in shaping the earliest colonization events of the microbiota.IMPORTANCEEarly life represents a critical window for microbial colonization of the human gastrointestinal tract. Surprisingly, we still know little about the rules that govern the successful colonization of infants and the factors that shape the success of early life microbial colonizers. In this study, we report that metal availability is an important factor in the assembly and succession of the early life microbiota. We show that the host-derived metal-chelating protein, calprotectin, is highly abundant in infants and successful early life colonizers can overcome metal restriction. We further demonstrate that feeding modality (breastmilk vs formula) markedly impacts metal levels in the gut, potentially influencing microbial community succession. Our work suggests that metals, a previously unexplored aspect of early life ecology, may play a critical role in shaping the early events of microbiota assembly in infants.

Electrochemistry enhanced multi-stage biological contact oxidation treating sulfamethoxazole wastewater: Performance, degradation pathway and microbial community

Clean and economical techniques are in urgent need for improving antibiotics removal from wastewater. In this study, a multi-stage bio-contact oxidation reactor (BCOR) was constructed and further enhanced by electrochemistry to treat sulfamethoxazole (SMX) wastewater. The stimulatory effects of the electrochemistry were investigated together with the succession of microbial communities as well as the possible conversion pathways of SMX. The results showed that the SMX and chemical oxygen demand removal rates reached up to 92.96 ± 0.62 % and 91.42 ± 0.82 % at electric current density of 2.0 mA/cm2. Electrochemistry enhancement induced bone cleavage and oxidation transformation pathways of SMX while reduced the toxicity of degrading intermediates. Moreover, electrochemistry enhancement stimulated the growth of Klebsiella and Rhodobacter as well as the fermentation, chemoheterotrophy and aerobic_chemoheterotrophy functions which further promoted the SMX removal. This study revealed the biochemical removal mechanisms of SMX degradation and manifested the feasibility of combing electrochemistry with BCOR to treat antibiotics wastewater with low energy consumption.

Effect of mineral additives and ammonia-oxidizing bacteria additions on physicochemical properties, nitrogen retention and microbial dynamics during vermicomposting of chicken manure and green waste

Vermicomposting is an effective technology to transform organic wastes into organic fertilizers. However, a large amount of nitrogen will be lost through ammonia (NH3) volatilization during verimicomposting. Herein, we investigated the effects of mineral additives (diatomite, zeolite) and exogenous ammonia-oxidizing bacteria (AOB) (Nitrosomonas europaea, Nitrosospira multiformis) added individually or combinedly on the physicochemical changes, the conversion of nitrogen, and the resident microbial community succession during chicken manure and green waste co-vermicomposting. The results showed that the combined addition of AOB and mineral additives significantly improved vermicompost quality and maturity in terms of humus, carbon/nitrogen ratio, humic acid/fulvic acid ratio and germination index. Compared with the control, jointly adding AOB and mineral additives reduced NH3 emissions by 65.72∼71.05 %, accelerated the conversion of NH4+-N to NO3−-N, increased total nitrogen content by 23.22∼25.21 %. The combination of AOB and mineral additives significantly increased the activities of ammonia monooxygenase, hydroxylamine oxidase, and nitrate oxidoreductase, and enhanced the amount of AOB community. Additionally, the combined addition of AOB and mineral additives increased bacterial richness and diversity, accompanied by increased relative abundances of Luteimonas, Cellvibrio, Saccharimonadales, and Pseudomonas. These microbial shifts were correlated with enhanced lignocellulose degradation, organic phosphate mineralization, and promotion of plant growth. Moreover, vermiompost-based growing media with mineral additives and AOB can significantly promote the growth of purple cabbage as compared to the vermicompost without additives. Overall, the synergistic use of AOB and mineral additives (diatomite, zeolite) was recommended as a favorable approach for reducing nitrogen losses and improving the efficiency of chicken manure and green waste vermicomposting. This study offers a novel approach to mediate nitrogen transformation processes and reduce nitrogen loss.

Study on the Microbial Mechanisms of Enhancing Agaricus bisporus Growth through Inoculation with Pseudomonas putida

Introducing Pseudomonas putida optimizes the microbial community within the casing layer, thereby enhancing Agaricus bisporus growth. Nevertheless, the underlying mechanisms governing microbial community succession within the casing layer following microbial agent introduction remained elusive. This study delineated the interplay among microbial populations in the casing layer across the growth cycle of A. bisporus, comparing cohorts treated with P. putida (AP) against untreated controls (CK). The inoculation with Pseudomonas promoted the growth of A. bisporus, shortened its growth cycle, and linearly enhanced the relative abundance of key bacterial genera integral to its growth, including Flavobacterium, Rhodoferax, Pseudarthrobacter, and Vogesella (adjusted R2=0.238-0.866). Importantly, a positive correlation was identified between the proliferation of these beneficial bacteria and positive community cohesion (adjusted R2=0.353-0.838). Additionally, analysis of the symbiotic network topology within the AP group indicated a more stable community following inoculation. The niche results (AP=11.7672±1.8938, CK=11.0481±3.1273, P<0.05) underscored the positive impact of Pseudomonas inoculation on ecosystem dynamics. Concentrations of essential nutrients for A. bisporus growth, notably readily available phosphorus (On day 17, the AP group was 78.8333±1.26623 mg/kg, while the CK group was 30.0333±0.98658 mg/kg) and readily available potassium (On day 17, the AP group was 2693.9±14.79561 mg/kg, while the CK group was 1646.9333±10.71276mg/kg), were significantly elevated in the AP group. These enhancements strongly correlated with the increased abundance of pivotal microbial populations. Our research provided insights into the application of microbial inoculants to enhance the production of edible fungi.

Effect of temperature on the quality and microbial community during Daocai fermentation

Daocai is a traditional salted pickle in the southeastern region of Guizhou with a unique aroma, color, and taste. The quality of Daocai is greatly influenced by the fermentation temperature. In this study, high-throughput sequencing and headspace-gas chromatography-ion mobility spectrometry were used to investigate the changes in microbial community succession and volatile flavor compounds during Daocai fermentation under temperature-controlled (D group) and non-temperature-controlled (C group).We found that the predominant genera in the C group samples were Latilactobacillus(40.57 %), Leuconostoc(21.25 %), Cystofilobasidium(22.12 %), Vishniacozyma(23.89 %), and Leucosporidium(24.95 %), whereas Weissella(29.39 %), Lactiplantibacillus(45.61 %), Mucor(68.26 %), and Saccharomyces(23.94 %) were the predominant genera in the D group. A total of 92 VFCs were detected in Daocai samples, including 5 isothiocyanates, 16 esters, 14 alcohols, 24 aldehydes, 17 ketones, 3 acids, 2 pyrazines, 1 pyridines, 1 thiazoles, 3 furans, 4 alkenes, and 2 nitriles. Further analysis revealed Latilactobacillus, Leuconostoc, Lactococcus, Cystofilobasidium, Leucosporidium, Holtermanniella, and Dioszegia as key bacteria involved in flavor formation. They are closely related to the formation of flavors such as aldehydes, furans, pyridines, and alkenes. This study contributes to our understanding of the relationship between bacterial communities and the flavor formation during Daocai fermentation.

Responses of soil microbial metabolism, function and soil quality to long-term addition of organic materials with different carbon sources

Biochar and green manure have been widely applied in agricultural production and are important means to achieve sustainable agriculture. However, there is limited research systematically and comprehensively exploring the response of soil microbiota and the changes in soil metabolomics after the addition of two different carbon source amendments to the soil, and the differential mechanisms of soil metabolomics between them remain unclear. In this study, a long-term field experiment (initiated in 2019) was conducted to investigate the effects of biochar and green manure application on soil nutrients and soil functions driven by soil microbes. Compared to the pure fertilizer treatment, biochar increased soil total carbon by 14.54% to 27.04% and soil available potassium by 4.67% to 27.46%. Ryegrass significantly increased soil available phosphorus and organic matter. Under different fertilization regimes, the ecological niches of soil microbes changed significantly. Network analysis revealed that long-term ryegrass returning reduced the complexity of soil microbial networks. Ryegrass and biochar increased dispersal limitation in fungal assemblages (reaching 93.33% and 86.67%, respectively), with biochar particularly enhancing variable selection in bacterial assemblages (accounting for 53.33%). Variation partitioning analysis based on redundancy analysis indicated that humic substances had the highest explanatory power for microbial community variation, with humic substances explaining 38.49% of bacteria and 52.19% of fungi variation. The ryegrass treatment mainly changed the abundance of carbohydrates (CH), amines (AM), c (AH), and lipids (LP), while the BC treatment mainly altered the abundance of organic acids (AC), amines (AM), and carbohydrates (CH). Meanwhile, both treatments significantly reduced the bisphenol A, one of the soil pollutants. Ryegrass incorporation significantly increased the abundance of genes related to soil C, N, P, and S cycling, especially genes involved in carbon decomposition, while biochar significantly enhanced the abundance of nitrogen fixation genes nifH and Hao in soil. Random forest model results indicated that carbohydrates, alcohols, aromatics (AR), and ester (ES) were the main categories of metabolites in soil influenced by differential microbes, and Finegoldia served as a common important metabolic driving species. In summary, this study reveals the processes of soil function, microbial community succession, and metabolism driven by ryegrass and biochar, providing important insights for optimizing soil management and improving soil quality.Graphical

The succession of microbial community and distribution resistance gene in response to enrichment cultivation derived from a long-term toxic metal(loid)s polluted soil

Microbial communities as the most important and active component of soil play a crucial role in the geochemical cycling of toxic metal(loid)s in the Pb and Zn smelting site soils. However, the relationships between soil microbial communities and the fractions of toxic metal(loid)s and the succession of soil microbial community and functions after enrichment cultivation have rarely been analyzed. In this study, the diversity and composition of microbial communities in soils before and after enrichment cultivation were investigated by high-throughput sequencing. And the co-occurrence relationships between soil microbial community after enrichment cultivation and MRGs genes were also analyzed through the BacMet database. Results showed that the dominant genus in the soils was Lactobacillus and Stenotrophomonas. The soil microbial community exhibited a notable correlation with Cd, Pb, and As, among which Cd exerted the most profound impact. Alishewanella, Pseudomonas, Massilia and Roseibacillus were significantly correlated with the fraction of Cd. After enrichment cultivation, the number of genera decrease to 96. And the dominant genus changed to Acinetobacter, Bacillus, Comamonas, Lysobacter, and Pseudoxanthomonas. High abundance of metal resistance genes (MRGs) including zntA, fpvA, zipB, cadA, czcA, czcB, czcC, zntA, arsR, pstS and pstB was found in the microbial community after enrichment cultivation. The potential host genus for MRGs was Acinetobacter, Comamonas, Lysinibacillus, Azotobacter, Bacillus, Lysobacter, Cupriavidus, Pseudoxanthomonas, and Thermomonas. Additionally, these microbial community after enrichment cultivation possessing pathways of bacterial chemotaxis and two-component systems was enabled them to adapt to the polluted environment. These observations provided potential guidance for microbe isolation and the development of strategies for the bioremediation of toxic metal(loid)s polluted soils.

Effect of inoculum sources on caproic acid production from food waste through lactate-based chain elongation: Properties and microbial succession

Caproic acid (CA) production is a promising way to valorize food waste (FW), but the low CA yield seriously restricts its application. Inoculum source as a key factor can affect the microbial communities and CA fermentation processes, but was not fully explored. In the present study, three common inoculum sources namely anaerobic digestion sludge (AD), pit mud (PM) and raw FW (RFW) were selected as inocula to initiate CA production from FW. The organics conversion properties, microbial community succession processes and bacterial metabolism pathways were investigated. Results showed that carbohydrates were effectively degraded into lactic acid and then to CA based on lactate-based chain elongation. The CA yield (0.37 g-COD/g-VS) using AD was higher than that inoculated with PM (0.26 g-COD/g-VS) and RFW (0.32 g-COD/g-VS). Although microbial communities in inocula were totally different, they exhibited similar succession with Firmicutes and Bacteroidetes as the dominant functional phyla. Logically, lactic acid-producing bacteria (e.g. Lactobacillus, Limosilactobacillus and Sporolactobacillus) were enriched at the early stage to prepare electron donor (lactate), and then were replaced by chain elongation bacteria for CA production. However, unclassified_Ruminococcaceae was dominant in reactor with AD, unclassified_Ruminococcaceae, Bifidobacterium, Clostridium_sensu_stricto and unclassified_Prevotellaceae were largely detected in reactors inoculated with PM and RFW, which resulted in different CA yield. This study provides useful information for caproate production from FW, and widens the knowledge of cleaner production from wastes.

Biological Decline of Alfalfa Is Accompanied by Negative Succession of Rhizosphere Soil Microbial Communities.

The growth and biological decline of alfalfa may be linked to the rhizosphere microbiome. However, plant-microbe interactions in the rhizosphere of alfalfa and associated microbial community variations with stand age remain elusive. This study explored the successional pattern of rhizosphere microbial communities across different aged alfalfa stands and its relationship with alfalfa decline. Rhizosphere soils were collected from 2- and 6-year-old alfalfa stands. Control soils were collected from interspaces between alfalfa plants in the same stands. Soil bacterial and fungal communities were characterized by 16S and ITS rRNA gene sequencing, respectively. Specific microbial taxa colonized the rhizosphere soils, but not the control soils. The rhizosphere-specific taxa mainly included potentially beneficial genera (e.g., Dechloromonas, Verrucomicrobium) in the young stand and harmful genera (e.g., Peziza, Campylocarpon) in the old stand. Alfalfa roots regulated soil microbial communities by selective promotion or inhibition of distinct taxa. The majority of time-enriched taxa were reported as harmful fungi, whose relative abundances were negatively correlated with plant traits. Time-depleted taxa were mostly known as beneficial bacteria, which had relative abundances positively correlated with plant traits. The relative abundances of functional bacterial genes associated with vancomycin biosynthesis, zeatin biosynthesis, and amino acid metabolism trended lower in rhizosphere soils from the old stand. An upward trend was observed for fungal pathogens and wood saprotrophs with increasing stand age. The results suggest that root activity drives the negative succession of rhizosphere microbial communities during alfalfa decline in old stands.

Successions of Bacterial and Fungal Communities in Biological Soil Crust under Sand-Fixation Plantation in Horqin Sandy Land, Northeast China

Biological soil crusts (BSCs) serve important functions in conserving biodiversity and ecological service in arid and semi-arid regions. Afforestation on shifting sand dunes can induce the formation of BSC on topsoil, which can accelerate the restoration of a degraded ecosystem. However, the studies on microbial community succession along BSC development under sand-fixation plantations in desertification areas are limited. This paper investigated the soil properties, enzymatic activities, and bacterial and fungal community structures across an age sequence (0-, 10-, 22-, and 37-year-old) of BSCs under Caragana microphylla sand-fixation plantations in Horqin Sandy Land, Northeast China. The dynamics in the diversities and structures of soil bacterial and fungal communities were detected via the high-throughput sequencing of the 16S and ITS rRNA genes, respectively. The soil nutrients and enzymatic activities all linearly increased with the development of BSC; furthermore, soil enzymatic activity was more sensitive to BSC development than soil nutrients. The diversities of the bacterial and fungal communities gradually increased along BSC development. There was a significant difference in the structure of the bacterial/fungal communities of the moving sand dune and BSC sites, and similar microbial compositions among different BSC sites were found. The successions of microbial communities in the BSC were characterized as a sequential process consisting of an initial phase of the faster recoveries of dominant taxa, a subsequent slower development phase, and a final stable phase. The quantitative response to BSC development varied with the dominant taxa. The secondary successions of the microbial communities of the BSC were affected by soil factors, and soil moisture, available nutrients, nitrate reductase, and polyphenol oxidase were the main influencing factors.

Quality changes and spoilage microbial community succession of steamed cold noodles (Liangpi) at different temperatures

Steamed cold noodles (Liangpi) are traditional high-moisture starchy foods that are widely consumed in China for their refreshing taste. However, the relationships between the microbial community and the changes in the quality and flavor of Liangpi during storage have not been elucidated. Low-temperature storage (11 °C) effectively inhibited the growth of microorganisms and maintained the moisture and color of Liangpi, but as the hardness increased, the springiness and chewiness decreased rapidly. Short-term storage at 25 °C and 37 °C did not significantly change the color or texture, but the number of microorganisms increased immediately. After 12 h at 37 °C, the total plate count increased by 5.3 log CFU/g. Volatile organic compound (VOC) analysis revealed that after 1 day of storage at 11 °C, 25 °C, and 37 °C, 2-pentylfuran disappeared, and the contents of alcohols, ketones, esters, and olefins increased significantly. The microbial diversity results revealed that Bacillus was the absolute dominant bacterial genus at 25 °C and 37 °C, Acinetobacter was the dominant genus at 11 °C, and Byssochlamys and Sporidiobolus were the dominant fungal groups causing spoilage, which may contribute to the production of VOCs associated with their off-flavor nature during storage. These results provide a reference for optimizing storage conditions to extend the shelf-life of Liangpi.

Microbial community dynamics in different floc size aggregates during nitrogen removal process upgrading in a full-scale landfill leachate treatment plant

Upgrading processes to reduce biodegradable organic substance addition is crucial for treating landfill leachate with high pollutant concentrations, aiding carbon emission reduction. Aggregate size in activated sludge processes impacts pollutant removal and sludge/water separation. This study investigated microbial community succession and driving mechanisms in different floc-size aggregates during nitrogen removal progress upgrade from conventional to partial nitrification–denitrification in a full-scale landfill leachate treatment plant (LLTP) using 16S rRNA gene sequencing. The upgrade and floc sizes significantly influenced microbial diversity and composition. After upgrading, ammonia-oxidizing bacteria were enriched while nitrite-oxidizing bacteria suppressed in small flocs with homogeneity and high mass transfer efficiency. Larger flocs enriched Defluviicoccus, Thauera, and Truepera, while smaller flocs enriched Nitrosomonas, suggesting their potential as biomarkers. Multi-network analyses revealed microbial interactions. A deep learning model with convolutional neural networks predicted nitrogen removal efficiency. These findings guide optimizing LLTP processes and understanding microbial community dynamics based on floc size.

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.

Cattle manure composting driven by a microbial agent: A coupled mechanism involving microbial community succession and organic matter conversion

Aerobic composting has been used as a mainstream treatment technology for agricultural solid waste resourcing. In the present study, we investigated the effects and potential mechanisms of the addition of a microbial agent (LD) prepared by combining Bacillus subtilis, Bacillus paralicheniformis and Irpex lacteus in improving the efficiency of cattle manure composting. Our results showed that addition of 1.5 % LD significantly accelerated compost humification, i.e., the germination index and lignocellulose degradation rate of the final compost product reached values of 92.20 and 42.29 %, respectively. Metagenomic sequencing results showed that inoculation of cattle manure with LD increased the abundance of functional microorganisms. LD effectively promoted the production of humus precursors, which then underwent reactions through synergistic abiotic and biotic pathways to achieve compost humification. This research provides a theoretical basis for the study of microbial enhancement strategies and humus formation mechanisms in the composting of livestock manure.

Influence of spatial and temporal diversity and succession of microbial communities on physicochemical properties and flavor substances of soy sauce

In this study, the influence and relationship between the microbial structure composition at different spatial locations during soy sauce fermentation and the quality of soy sauce were investigated. Within 3–7 days of fermentation, the abundance of Chromohalobacter in the surface and upper layers of moromi was initially high but subsequently decreased. In contrast, Tetragenococcus exhibited low abundance on the surface of moromi at the beginning of fermentation but emerged as the absolute dominant bacteria by the end of the fermentation process. Throughout the fermentation period of 3–42 days, Staphylococcus and Bacillus were the predominant bacterial genera observed at the bottom of the moromi. In addition, Halanaerobium was the dominant bacterial genus in the crude soy sauce layer throughout the fermentation process. Tetragenococcus and Zygosaccharomyces were strongly positively correlated with total acid and ammonia nitrogen. Bacillus and Staphylococcus were significantly negatively correlated with the salt content.

Microbial community succession and antibiotic resistance gene response during the one-step startup of thermophilic UASB

A thermophilic anaerobic up-flow anaerobic sludge bed (UASB) was rapidly established from a mesophilic reactor in 25 days by directly increasing the operation temperature from 35 to 55℃. The succession of methanogenic microbial community and response of antibiotic resistance genes (ARGs) during the startup period were revealed by 16S rRNA gene amplicon sequencing and metagenomics analysis. After the temperature was increased, thermophilic hydrotropic Methanothermobacter outgrew aceticlastic Methanosaeta and the mesophilic hydrotropic methanogens (Methanobacterium and Methanolinea), with its abundance increasing from 3.19 % on day 7 to 72.33 % on day 10. Meanwhile, Exilispira, an acetate-oxidizing bacterium, proliferated quickly in the fermenter community concurrently with the growth of Methanothermobacter, indicating that the syntrophic relationship between acetate-oxidizing organisms and hydrogenotrophic methanogens is the primary pathway for methane production in thermophilic UASB. As for ARGs, the abundance of the resistome of the anaerobic sludge decreased after the hike in temperature, driven by the succession of the methanogenic community, confirming the benefit of thermophilic treatment for antimicrobial resistance control. The results proved that a thermophilic UASB could be rapidly constructed by a one-step startup strategy due to the fast establishment of the syntrophic acetate oxidation pathway, and maintain better ARG control performance than its mesophilic counterpart.

Elucidating biofouling development and succession in membrane distillation using treated effluent

Biofouling in membrane distillation (MD) has several repercussions, including reduced efficiency of the MD process and limiting membrane life. Additionally, the evaluation of MD biofouling using treated effluents from wastewater treatment plants remains an unexplored area. Thus, biofouling formation and development in a long term MD process (15 days) using treated effluent from a wastewater treatment plant was explored in this study. The results revealed that flux decline occurred in four phases: i) initial decline (0–1 d), ii) gradual decline (1–5 d), iii) progressive decline (5–10 d), and iv) rapid decline (10–15 d). Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis demonstrated that the treated effluent contained humic-like substances, which deposited on the membrane surface in phase 1. Whereas biopolymers development on the membrane surface in phase 2 and 3 was linked to biofouling. Microbial community analysis revealed that the initial colonisers were predominantly thermophilic bacteria, which were different from the microbial community of the treated effluent. The biofilm-forming bacteria included Schlegelella, Meiothermus, and Vulcaniibacterium. These microorganisms proliferate and release excessive extracellular polymeric substances (EPS), leading to the development of mature biofilm on membrane surface. This helped in the deposition of organics and inorganics from the bulk feed, which led to microbial community succession in phase 4 with the emergence of the Kallotenue genus. The results suggested that organic substances and microbial communities on membrane surface at different stages in a long-term MD process had a significant influence on MD performance for high-quality wastewater reuse.

Effects of cable bacteria on vertical redox profile formation and phenanthrene biodegradation in intertidal sediment responded to tide

Periodic oxygen permeation is critical for pollutant removal within intertidal sediments. However, tidal effects on the vertical redox profile associated with cable bacterial activity is not well understood. In this study, we simulated and quantified the effects of tidal flooding, exposing, and their periodic alternation on vertical redox reactions and phenanthrene removal driven by cable bacteria in the riverbank sediment. Results show that electrogenic sulfur oxidation (e-SOx) mediated by cable bacteria during exposing process drove the vertical permeation of oxidation potential characterized by a decrease in Fe(II) and sulfide concentrations. The sulfate produced was observed in deep sediment (5–10 mm) and served as an electron acceptor for anaerobic oxidation, thereby triggering the functional succession of microbial community. About 78.2 % and 80.8 % of phenanthrene was degraded in deep sediment where cable bacteria grew well under exposing and tidal conditions. Anaerobic processes during tidal flood were also found to be important for the survival of cable bacteria. Higher cable bacteria abundance (up to 1.5 %) was observed under tidal conditions compared to that under continuous exposing conditions and flooding conditions. This might be attributed to lower oxidation stress and sulfide replenishment via sulfate reduction while flooding. Under tidal conditions, the cable bacteria interacted with sulfate reduction bacteria (e.g. Desulfobacca spp. and Desulfatiglans spp.) and maintained the dynamic balance of HS− and SO42− in sediment profiles. This HS−-SO42− cycle could serve as a “redox connector” that continuously delivers oxidation potential to deep sediments, resulting in the removal of organic pollutants. The findings provide preliminary evidence of the self-purification mechanisms within intertidal sediments and suggest a potential strategy for sediment remediation.

Anaerobic fermentation for hydrogen production and tetracycline degradation: Biodegradation mechanism and microbial community succession

The misuse and continues discharge of antibiotics can cause serious pollution, which is urgent to take steps to remit the environment pollution. In this study, anaerobic bacteria isolated from the aeration tank of a local sewage treatment plant were employed to investigate hydrogen production and tetracycline (TC) degradation during anaerobic fermentation. Results indicate that low concentrations of TC enhanced hydrogen production, increasing from 366 mL to a maximum of 480 mL. This increase is attributed to stimulated hydrolysis and acidogenesis, coupled with significant inhibition of homoacetogenesis. Furthermore, the removal of TC, facilitated by adsorption and biodegradation, exceeded 90 %. During the fermentation process, twenty-one by-products were identified, leading to the proposal of four potential degradation pathways. Analysis of the microbial community revealed shifts in diversity and a decrease in the abundance of hydrogen-producing bacteria, whereas bacteria harboring tetracycline resistance genes became more prevalent. This study provides a possibility to treat tetracycline-contaminated wastewater and to produce clean energy simultaneously by anaerobic fermentation.

Activation of denitrification potential within anammox consortia to exceed nitrogen removal thresholds via Fe-Mn functionalized biochar: Enhanced interspecies electron transfer and metabolite cross-feeding

Anammox exerts a crucial role in nitrogenous effluents remediation; nevertheless, nitrogen removal efficiency thresholds triggered by additional nitrate production poses a critical obstacle for anammox performance. Herein, Fe-Mn functionalized biochar (FeMn#BC) was synthesized and incorporated into anammox consortia to elicit the exogenous organics-independent metabolic potential of denitrifying bacteria, which decreased nitrate accumulation and achieved up to 90.69 ± 0.48 % total nitrogen removal efficiency. Enzyme content analysis indicated that FeMn#BC bolstered biometabolic vigour and electron transport system activity by stimulating the synthesis of heme c and NADH. Microbial community succession results demonstrated that FeMn#BC facilitated the proliferation of anammox bacteria (AnAOB) and nitrate-reducing functional bacteria. Metagenomic analysis uncovered that FeMn#BC increased the relative abundance of genes related to energy metabolism, nutrient-substrate ingestion, cofactor synthesis, and iron-manganese transport pathways. Candidatus Brocadia sp013360945 interacted nitrogen metabolism substrates and electrons with dominated denitrifying species PR03 sp. (dependent on endogenous organics and FeMn#BC-released Fe(II)), while interacted cofactors with other mutualistic bacteria possessing nitrate-reducing potential (e.g. ATM1 sp003577165). FeMn#BC-released Mn(II) served as an additional electron donor, augmenting electron availability for non-dominant anammox species like Candidatus Jettenia caeni and Candidatus. Kuenenia stuttgartiensis. This research highlights the critical mechanism of Fe-Mn synergism for overcoming the bottleneck of anammox nitrogen removal efficiency, and demonstrates the substantial potential of Fe-Mn functionalized materials to revolutionize the existing wastewater treatment technologies towards a carbon-free approach.