Extracellular Polymeric Substances Research Articles

Simultaneous removal of heavy metals and inorganic nitrogen by using the biofilm of Marichromatium gracile YL28.

Heavy metal and nitrogen contaminations are serious concerns in aquatic environments. Marichromatium gracile YL28, a marine purple sulfur bacterium, has shown great potential as a bioremediation agent for removing inorganic nitrogen from marine water. This study further investigated its ability to simultaneously absorb heavy metals, including Pb(II), Cu(II), Cd(II) and Cr(VI), and remove inorganic nitrogen. The contributions of photopigment and extracellular polymeric substances (EPS) in the YL28 biofilm to heavy metal adsorption and tolerance were also evaluated. The YL28 biofilm demonstrated higher adsorption efficiencies for heavy metal ions than planktonic cells. A high level of EPS was detected in the biofilm. The effects of four heavy metal on the inhibition of photopigment synthesis showed that high concentrations of Cu(II) greatly inhibited the production of BChl a and Car. The adsorption efficiencies of Pb(II), Cu(II), Cd(II), and Cr(VI) in the YL28 biofilm reactor reached 86.59%, 72.94%, 80.06%, and 95.95%, respectively. Elevated concentrations of heavy metal ions only marginally impeded ammonia nitrogen removal; they impacted neither nitrite and nitrate removals nor hindered the simultaneous elimination of three inorganic nitrogen compounds. Coupled with their ability to remove inorganic nitrogen, the high adsorption capacity and tolerance of YL28 biofilms toward heavy metal suggest a promising solution for mitigating metal pollutants.

Ammonia nitrogen affects bacterial virulence and conditional pathogenic bacterial growth by regulating biofilm microbial metabolism and EPS secretion in laboratory scale distribution systems.

The control of conditional pathogenic bacteria and inhibition of their virulence factors (VFs) in drinking water distribution systems (DWDSs) is vital for drinking water safety. This study adopted two groups of DWDSs to investigate how ammonia nitrogen affects bacterial VFs and conditional pathogenic bacterial growth in biofilms. Our results indicated that Acidimicrobium (95,916.62±119.24 TPM), Limnohabitans (30,338.81±139.14 TPM), and Sediminibacterium (10,658.01±48.94 TPM) were predominant in the biofilm bacterial community of DWDSs with NH3-N addition. Under these conditions, the abundances of various bacterial metabolites, such as L-glutamate (1.45-fold), 2-oxoglutarate (1.24-fold), pyruvate (2.10-fold), and adenosine monophosphate (AMP, 5.29-fold), were significantly upregulated, which suggested the upregulation of amino acid, carbohydrate, nucleotide, lipid, pyrimidine and purine metabolism. These metabolic pathways accelerated extracellular polymeric substance (EPS) secretion. The protein concentration in EPS also increased to 187.59±0.58μg/cm2. The increased EPS secretion promoted the amide I CO group of the EPS protein to interact with the surface of the DWDSs, thus enhancing the ability of bacteria (especially conditional pathogenic bacteria) to adhere to the pipe surface to form biofilms. Due to EPS protection, the abundance of the adherence subtype of VFs and the plate counts of Pseudomonas aeruginosa increased to 5912.8±21.89 TPM and 655.78±27.10CFU/cm2, respectively. Therefore, NH3-N in DWDSs increased bacterial VFs levels and promoted the growth of some conditional pathogenic bacteria by regulating biofilm microbial metabolic pathways and EPS secretion, ultimately impacting the interaction between EPS and the pipe surface.

Were early Archean carbonate factories major carbon sinks on the juvenile Earth?

Abstract. Paleoarchean carbonates in the Pilbara Craton (Western Australia) are important archives for life and environment on early Earth. Amongst others, carbonates occur in interstitial spaces of ca. 3.5–3.4 Ga pillow basalts (North Star, Mount Ada, Apex, and Euro Basalt, Dresser Formation) and are associated with bedded deposits (Dresser and Strelley Pool Formation, Euro Basalt). This study aims to understand the formation and geobiological significance of those early Archean carbonates by investigating their temporal–spatial distribution, petrography, mineralogy, and geochemistry (e.g., trace elemental compositions, δ13C, δ18O). Three carbonate factories are recognized: (i) an oceanic crust factory, (ii) an organo-carbonate factory, and (iii) a microbial carbonate factory. The oceanic crust factory is characterized by carbonates formed in void spaces of basalt pillows (referred to as “interstitial carbonates” in this work). These carbonates precipitated inorganically on and within the basaltic oceanic crust from CO2-enriched seawater and seawater-derived alkaline hydrothermal fluids. The organo-carbonate factory is characterized by carbonate precipitates that are spatially associated with organic matter. The close association with organic matter suggests that the carbonates formed via organo-mineralization – that is, linked to organic macromolecules (either biotic or abiotic), which provided nucleation sites for carbonate crystal growth. Organo-carbonate associations occur in a wide variety of hydrothermally influenced settings, ranging from shallow marine environments to terrestrial hydrothermal ponds. The microbial carbonate factory includes carbonate precipitates formed through mineralization of extracellular polymeric substances (EPSs) associated with microbial mats and biofilms. It is commonly linked to shallow subaquatic environments, where (anoxygenic) photoautotrophs might have been involved in carbonate formation. In the case of all three carbonate factories, hydrothermal fluids seem to play a key role in the formation and preservation of mineral precipitates. For instance, alkaline Earth metals and organic materials delivered by fluids may promote carbonate precipitation, whilst soluble silica in the fluids drives early chert formation, delicately preserving authigenic carbonate precipitates and associated features. Regardless of the formation pathway, Paleoarchean carbonates might have been major carbon sinks on the early Earth, as additionally suggested by carbon isotope mass balances indicating a carbon flux of 0.76–6.5 × 1012 mol yr−1. Accordingly, these carbonates may have played an important role in modulating the carbon cycle and, hence, climate variability on the early Earth.

Programming Surface Motility and Modulating Physiological Behaviors of Bacteria via Biosurfactant-Mimetic Polyurethanes.

Modulating microbial motility and physiology can enhance the production of bacterial macromolecules and small molecules. Herein, a platform of water-soluble and amphiphilic peptidomimetic polyurethanes is reported as a means of regulating bacterial surface behavior and the concomitant production of extracellular polymeric substances (EPS). It is demonstrated that carboxyl (-COOH)-containing polyurethanes exhibited 17-fold and 80-fold enhancements in Pseudomonas aeruginosa (P. aeruginosa) swarming and twitching areas, respectively. Conversely, an amine (-NH2)-functionalized polyurethane reduces the P. aeruginosa swarming area by 58%. Similar influences on the surface motility of Escherichia coli (E. coli) and a nonswarming P. aeruginosa mutant strain are also observed. Notably, -COOH polyurethanes completely wet the agar hydrogel surface and promote bacterial surface proliferation, resulting in enhanced EPS and rhamnolipid production. The programming of bacterial spatial migration into designed patterns is achieved by leveraging the opposing influences of -NH2 and -COOH polyurethanes. The results highlight the potential of this synthetic polyurethane platform and potentially other polymer systems as an exciting approach to control bacterial surface behaviors and influence the production of engineered living materials.

Spatiotemporal Mapping of the Evolution of Silver Nanoparticles in Living Cells.

Bioaccumulated silver nanoparticles (AgNPs) can undergo transformation and release toxic Ag+, which can be further reduced and form secondary AgNPs (Ag0NPs). However, the intricate interconversions among AgNPs, Ag+, and Ag0NPs remain speculative. Herein, we developed a bioimaging method by coupling the aggregation-induced emission method with the label-free confocal scattering and hyperspectral imaging techniques to quantitatively visualize the biodistribution and biotransformation of AgNPs, Ag0NPs, and Ag+ in living cells. We demonstrated that AgNPs were first dissolved in the medium, and the released Ag+ was converted into Ag0NPs with the presence of algal extracellular polymeric substances and light. Under these conditions, AgNPs alone accounted for 12.4% of the total AgNP toxicity, a percentage comparable to that of Ag0NPs (15.6%). However, Ag+ remained the primary contributor to overall AgNP toxicity. Additionally, we found that about 9.00% of the accumulated AgNPs within the algal cells were transformed after 24 h exposure. Of these transformed AgNPs, 4.70% remained as Ag+ forms (located in the apical region, nucleus, and pyrenoid), while 4.30% persisted as Ag0NP forms (located in the cytosol) that were only detectable after a 4 h exposure. We further showed that AgNP exposure upregulated algal glutathione production with a 38.3-fold increase in glutathione reductase activity, which potentially resulted in Ag0NP formation at the active site. Overall, this study differentiated the toxicity of AgNPs, Ag+, and Ag0NPs and directly visualized the ongoing transformation and translocation of AgNPs, Ag+, and Ag0NPs within living cells, which are critical in unveiling the toxicity mechanisms of AgNPs.

A comprehensive review of antibiotics stress on anammox systems: Mechanisms, applications, and challenges.

Anaerobic ammonia oxidation (anammox), an energy-efficient technology for treating ammonium-rich wastewater, faces the challenge of antibiotic stress in sewage. This paper systematically evaluated the impact of antibiotics on anammox by considering both inhibitory effects and recovery duration. This review focused on cellular responses, including extracellular polymeric substances (EPS), quorum sensing (QS), and enzymes. Then, the physiological properties of cells and the interactions between nitrogen and carbon metabolism under antibiotic stress were discussed, particularly within the anammoxosome. The microbial community evolution and the development and transfer of antibiotic resistance genes (ARGs) were further analyzed to reveal the resistance mechanisms of anammox. To address the limitations imposed by antibiotics, the development of bio-augmentation and combined processes based on molecular biology techniques, such as bio-electrochemical systems (BES), has been suggested. This review offered new insights into the mechanisms of antibiotic inhibition during the anammox process and aimed to advance their engineering applications.

Inhibition of disinfection byproducts formation and microbial stress responses by Cu-Al/coconut shell activated carbon biofiltration: The key role of Al species

The effects of biological activated carbon treatment using CuAl bimetallic modified coconut shell activated carbon (CAAC) were investigated on the formation of disinfection by-products (DBPs) and microbial stress responses with unmodified granular coconut shell activated carbon (GAC) as a reference. In the long-term biological filtration process, the formation potentials of trihalomethanes and haloacetic acids in the effluent of CAAC filter (ACW) was reduced by 63.58 % compared to the effluent of GAC filter (CW). After the 6th day of biofilter operation, the dissolved organic carbon concentration of ACW rapidly decreased to around 1.03 mg/L and was consistently lower than that of CW. Under the enhanced biological flocculation by Al species, the extracellular polymeric substances (EPS) on the CAAC surface exhibited higher content and stronger flocculation efficiency, making the biofilm denser and more difficult to detach into ACW. In addition, the developed biofilms on CAAC surface promoted the biodegradation of organic compounds including DBPs precursors. Interestingly, the coexistence of Cu and Al mitigated the stimulatory effect of Cu, resulting in less intracellular reactive oxygen species and EPS. Our findings revealed that as a biofilter carrier filler, CAAC can effectively improve water quality and continuously control the risk of DBPs in the subsequent transmission and distribution process. More importantly, the introduction of Al species can provide new ideas to promote the realistic application of various modified treatment materials that are stressful to microorganisms.

Enhancing nitrogen removal from real oxytetracycline pharmaceutical wastewater via partial nitrification and post-denitrification (PNPDE) process: Insights into performance, mechanism, and application

Economically and efficiently removing nitrogen from oxytetracycline pharmaceutical wastewater (OPW) is a challenging problem. To address this, this study established an anaerobic-oxic-anoxic sequencing batch reactor, integrating a process involving partial nitrification (PN) and post-denitrification (PDE) to treat OPW (PNPDE). When the average total nitrogen in the influent was 110 mg/L, the effluent nitrogen level, nitrite accumulation ratio, and nitrogen removal efficiency were 12.7 mg/L, 95.1 %, and 88.7 %, respectively. Extracellular polymeric substances (EPS) played a crucial role in PNPDE stability and oxytetracycline degradation; EPS increased from 34.1 to 66.3 mg/gVSS during operation. In a typical cycle, exogenous denitrification, simultaneous nitrification-denitrification, and endogenous denitrification were the main nitrogen removal pathways, contributing 19.8 %, 21.3 %, and 48.7 %, respectively, of nitrogen removal. Meanwhile, 41.2 % of oxytetracycline was degraded, generating eight low-toxic biotransformation products. High-throughput sequencing results indicated that functional microorganisms, such as Nitrosomonas, Ellin6067, OLB8, Candidatus_Competibacter, Persicitalea, and Thauera, played a crucial role in removing nitrogen and degrading OTC. PNPDE provides a novel solution for effective and energy-saving OPW treatment.

Ultrasound Treatment Combined with Rhamnolipids for Eliminating the Biofilm of Bacillus cereus

Biofilm formation by Bacillus cereus is a major cause of secondary food contamination, leading to significant economic losses. While rhamnolipids (RLs) have shown effectiveness against Bacillus cereus, their ability to remove biofilms is limited when used alone. Ultrasound (US) is a non-thermal sterilization technique that has been found to enhance the delivery of antimicrobial agents, but it is not highly effective on its own. In this study, we explored the synergistic effects of combining RLs with US for biofilm removal. The minimum biofilm inhibitory concentration (MBIC) of RLs was determined to be 32.0 mg/L. Using a concentration of 256.0 mg/L, RLs alone achieved a biofilm removal rate of 63.18%. However, when 32.0 mg/L RLs were combined with 20 min of US treatment, the removal rate increased to 62.54%. The highest biofilm removal rate of 78.67% was observed with 256.0 mg/L RLs and 60 min of US exposure. Scanning electron microscopy analysis showed that this combined treatment significantly disrupted the biofilm structure, causing bacterial deformation and the removal of extracellular polymeric substances. This synergistic approach not only inhibited bacterial metabolic activity, aggregation, and adhesion but also reduced early biofilm formation and decreased levels of extracellular polysaccharides and proteins. Furthermore, US treatment improved biofilm permeability, allowing better penetration of RLs and interaction with bacterial DNA, ultimately inhibiting DNA synthesis and secretion. The combination of RLs and US demonstrated superior biofilm removal efficacy, reduced the necessary concentration of RLs, and offers a promising strategy for controlling biofilm formation in the food industry.

Manuscript for: Journal of Environmental Chemical Engineering New insights into the influence of ultrafiltration pretreatment on reverse osmosis membrane fouling during urban sewage reclamation: Interaction between extracellular polymeric substances and inorganic foulants

Ultrafiltration (UF) has been frequently employed as pretreatment to mitigate reverse osmosis (RO) membrane fouling. The organic and inorganic substances outflowing from UF pretreatment collectively determine the subsequent RO membrane fouling behavior. However, most of the previous studies were focused on single organic compounds as well as CaSO4 scaling, yet complex organic matter such as extracellular polymeric substances (EPS) and various inorganic scaling (i.e. CaCO3, Ca3(PO4)2) coexisted during urban sewage reclamation. In this study, the impact of UF pretreatment on RO membrane fouling behavior, especially the interaction between EPS and CaCO3/Ca3(PO4)2 scaling, were systematically investigated. Results showed that the presence of UF significantly reduced the normalized flux decline (9.3% vs. 14.3%) and enhanced cleaning recovery efficiency (84.6% vs. 51.6%) of RO membrane, but increased scattered crystals (CaCO3 and Ca3(PO4)2) formation on RO membrane surface. Further investigation showed that the binding energy of the Ca2p1/2 and Ca2p3/2 peaks on fouled RO membrane exhibited a shift towards lower energy, which indicated a weak complexation between EPS and Ca2+, thereby increasing inorganic scaling and confirming the two-sides role of EPS retained by UF in RO membrane fouling. Moreover, static experiments indicated that EPS inhibited CaCO3 scaling rather than Ca3(PO4)2 scaling with the inhibition rates of 7.3% and 0.7%, respectively. To the best of our knowledge, it is the first to reveal the different effect of EPS on CaCO3 and Ca3(PO4)2 scaling. The results may provide a new insight into the effect of UF pretreatment on RO membrane fouling during urban sewage reclamation process.

Study on substrates purification effect and microbial community structure of vertical subsurface flow constructed wetland under siphon effect

To explore the pollutants removal effects of siphon composite vertical flow constructed wetlands (Sc-VSsFCW), alongside the characteristics of microbial communities and the varying trends of extracellular polymeric substances (EPS) content across substrate layers. Two kinds of distinct Sc-VSsFCW, with loess sphere and clay ceramic grain as substrate materials, respectively, were established. During the experiment, water quality of influent and effluent were detected to investigate system pollutant removal efficiency, routine index detection, microbial diversity analysis and EPS content determination, and substrates were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results indicated that both substrate systems exhibited good pollutant removal effect, with the average removal rate of 90 % for ammonia nitrogen (NH4+-N), and chemical oxygen demand (COD) removal rate within the range of 60–70 %. The long-term re‑oxygenation process inherent in the system successfully augmented the dissolved oxygen (DO) content within the wastewater, and facilitate relative high abundance of Nakamurella, Bacillus, and Nitrospira in these two substrate systems, which enhanced organic matter degradation and nitrification processes. Moreover, the hydraulic conductivity and EPS content in both substrate systems displayed a declining trend, suggesting that the system's unique hydraulic conditions strategies effectively mitigated EPS accumulation and diminished the likelihood of biological clogging. Consequently, the system's distinctive re‑oxygenation and siphon drainage methods boast advantages over traditional vertical flow constructed wetlands in terms of enhancing dissolved oxygen levels and mitigating the risk of biological clogging. This study contributes theoretical underpinnings for the application of constructed wetlands in wastewater treatment and clogging mitigation.

PROBIOTIC AND β-LACTAM SENSITIVITY ASSESSMENT OF LACTIC ACID BACTERIA ISOLATED FROM TRADITIONALLY FERMENTED PRODUCTS OF MEGHALAYA

Objective: The present study aimed to isolate, identify, and analyze the probiotic properties and β-lactam sensitivity in the Lactic Acid Bacteria (LAB) prevalent in Tungtap and Lung-seij, common traditionally fermented ethnic products throughout Meghalaya. Methods: Bacterial pure colonies were identified using conventional biochemical tests and 16S rRNA Sanger sequencing. Slightly modified standard protocols were followed for the assessment of different probiotic properties. Results: The selected LAB isolates were found Gram-positive, catalase, and oxidase-negative and exhibited resistance to most of the β-lactam antibiotics used in this study. No significant antibacterial activity was shown against tested strains. However, they showed strong bile salt and acid tolerance, as well as high auto aggregation and moderate hydrophobicity properties, which represent their probiotics properties. Extracellular Polymeric Substances (EPS) yield was highest for the TT2 isolate, while TT10 showed maximal siderophore production. Biofilm formation varied, with BS2 and BS5 showing strong adherence. Sequencing results confirm that the majority of the isolates belonged to the Lactiplantibacillus and Ligilactibacillus genera. Moreover, further genetic analysis confirmed the presence of β-lactamase genes in the selected isolates. Conclusion: The presence of these genes suggests that the isolates may become reservoirs for Antimicrobial Resistance Genes (ARG) in traditional fermented foods. Further study is required to establish whether the isolates are transmitting their antimicrobial resistance genes during co-culture under different stress conditions and transportation.

The role of the proteosurfaceome and exoproteome in bacterial coaggregation.

Bacterial coaggregation is a critical process in multispecies biofilm formation, driven by specific molecular interactions that facilitate the adhesion and aggregation of bacterial cells. These interactions are essential for the development and persistence of complex microbial communities. This review provides a comprehensive analysis of the roles of the proteosurfaceome and exoproteome in bacterial coaggregation. The proteosurfaceome, comprising surface-bound molecules such as adhesins, drives species-specific interactions crucial for partner recognition and adhesion. In parallel, the exoproteome, particularly extracellular polymeric substances (EPS), enhances aggregate stability by reinforcing structural integrity and facilitating intercellular communication, although its direct role in coaggregation remains to be fully clarified. By integrating these perspectives, this review aims to elucidate how the proteosurfaceome and exoproteome influence bacterial coaggregation, offering insights into their combined impact on microbial community structure and function. Furthermore, we highlight existing knowledge gaps and propose directions for future research.

Effect of metal ions on moving bed biofilm reactor (MBBR) for nitrogen removal in wastewater: Performance characteristics, flocculation efficiency and bacterial community.

Advanced operational moving bed biofilm reactor (MBBR) has demonstrated to achieve simultaneous sludge yield minimization and pollutants removal. However, effect of different metal ions on MBBR performance for nutrients removal in wastewater under low carbon to nitrogen ratio is still unclear. Fate of NH4+-N and NO3--N by MBBR were explored under the influence of Mn(II), Cu(II), and Fe(II) at carbon to nitrogen ratio of 5. The result showed that Mn(II) and Fe(II) significantly improved the NH4+-N and TN removal with a removal ratio of 71.0% and 80.5%, and 77.8% and 87.5% compared to the absence of added metal ions, and Cu(II) reduced the nitrogen removal. Biofilm characteristics including extracellular polymeric substances (EPS), electron transport system activity, and reactive oxygen species were investigated. The result indicated that both Mn(II) and Fe(II) enhanced the extracellular polymeric substances activity, electron transfer, and flocculation efficiency and hydrophilicity of biofilm. Furthermore, nitrification and denitrification processes of MBBR were further evaluated by X-ray photoelectron spectroscopy, fourier transform infrared reflection, cyclic voltammetry, differential pulse voltammetry, and Tafel curves. The result revealed that the main functional groups (e.g., C=O, C-O, and O-C=O bonds), and manganese and iron cycling might be involved in the nitrogen and metal ions removal. Finally, microbial community and co-occurrence network of biofilm were studied, showing that Proteobacteria and Bacteroidetes were identified as the dominant phyla for nitrogen and metal ions removal. This study aimed to provide the technical support for the startup and engineering applications of MBBR in wastewater treatment.

Improving methane production from waste-activated sludge by coupling thermal hydrolysis with potassium ferrate pretreatment

Thermal hydrolysis (TH) is effective in improving the solubilization of waste-activated sludge, but opportunities for enhancement remain, particularly in increasing organic matter conversion and reducing the generation of refractory substances. This study proposed a novel pretreatment method combining TH and potassium ferrate (PF) and evaluated its performance in improving sludge methane production. The results indicated that the combined pretreatment increased the methane yield from 118 ± 2 mL/g VS to 215 ± 7 mL/g VS, an increase of 82.2 % compared to the control. Combined pretreatment promoted the exposure of functional groups in the extracellular polymeric substances (EPS) and altered protein secondary structure composition, thereby disrupting EPS. PF improved the biodegradability of TH-treated sludge by degrading humic acids and Maillard reaction products. In addition, Fe(III) produced by PF induces dissimilar iron reduction, which enhances microbial electron transfer activity and facilitates subsequent hydrolysis and acidification processes. Combined pretreatment increased the abundance of hydrolyzing and acidifying bacteria, but reduced hydrogenotrophic methanogens. This article reveals that PF improves the biodegradability of TH-treated sludge and provides new ideas for advanced TH technologies for sludge resource recovery.

Silica-coated nano zero-valent iron as a slow-release electron donor for sustained enhancement of aerobic denitrification in oligotrophic source water: Performance and mechanism

Limited organic carbon in drinking water constrains the removal of nitrate‑nitrogen (NO3−-N) via aerobic denitrification. This paper reports the use of silica-coated nano zero-valent iron (nZVI@SiO2) as a stable and sustainable electron donor to enhance aerobic denitrification. The nZVI@SiO2, synthesized via a one-step method, was resistant to oxidation and exhibited excellent stability. In conjunction with aerobic denitrifying bacteria, nZVI@SiO2 achieved NO3−-N and total nitrogen TN removal efficiencies of 90.64 % and 80.94 %, respectively. This represents an increase of 24.15 % in the efficiency of TN removal compared with that of the nZVI system. The activity of the nZVI system diminished gradually after just three cycles, whereas nZVI@SiO2 maintained NO3−-N and TN removal efficiencies of 89.33 % and 78.08 %, respectively, after four cycles, respectively, indicating its sustainable ability to enhance aerobic denitrification. Cyclic voltammetry and electrochemical impedance spectroscopy demonstrated enhanced electron transfer efficiency of nZVI@SiO2. Furthermore, nZVI@SiO2 significantly promoted the activity of the electron transfer system, ATP levels, nitrate/nitrite reductase activity, contents of complexes I and III, and extracellular polymeric substances. nZVI@SiO2 significantly enhanced electron generation, transfer, and consumption during biological denitrification by functioning as both an electron donor and mediator. The findings implicate nZVI@SiO2 as a means to enhance nitrogen removal by aerobic denitrifying microorganisms in oligotrophic water via sustained donation of electrons.

Ecological response mechanism of alkaline wastewater periphytic biofilms to pH alteration

The environmental impact of indiscriminate alkaline wastewater discharge is increasingly concerning. Studying the ecological response mechanisms of periphytic biofilms to such wastewater is crucial for deepening our understanding of its broader environmental implications. In this study, periphytic biofilms collected from the drainage outlet of a tunnel construction project were developed for 56 days at initial pH values of 10 (pH0 10) and 12 (pH0 12). These stabilized biofilms were then transferred to a neutral environment (pH 7) for another 35 days. High-throughput 16S rRNA sequencing revealed changes in the growth characteristics, microbial interactions, and microbial community composition, function, and assembly patterns of the biofilms. Specifically, results revealed decreased microbial activity, live/dead bacteria ratios, and polysaccharide content in extracellular polymeric substances when the pH was reduced from alkaline to neutral, with incomplete recovery observed after 35 days of incubation in a neutral environment. During neutral pH incubation, proteobacterial abundance increased by 58.39 % and 33.08 % in biofilms cultured at pH0 10 and pH0 12, respectively, becoming the dominant flora, with chemoheterotrophic functions increasing by 8.11 % and 38.23 %, respectively. Network analysis indicated that biofilms in the pH0 12 culture group had a more advanced organizational co-occurrence network, with more complex and stable interactions, than those in the pH0 10 culture group. Microbial community α diversity, key differential species count, the proportion of positively correlated network edges, and null model data showed that microbial communities in biofilms cultured at pH0 10 were more resilient, whereas those cultured at pH0 12 were more resistant. Overall, this study reveals that alkaline wastewater periphytic biofilms adapt and develop high tolerance and metabolic activity but struggle to recover their original state in a short-term neutral environment, with biofilms cultured at pH0 12 exhibiting more complex interactions and higher resistance and those cultured at pH0 10 showing greater resilience.

Phage-liposome nanoconjugates for orthopedic biofilm eradication

Infection by multidrug-resistant (MDR) bacteria has become one of the biggest threats to public health worldwide. One reason for the difficulty in treatment is the lack of proper delivery strategies into MDR bacterial biofilms, where the thick extracellular polymeric substance (EPS) layer impedes the penetration of antibiotics and nanoparticles. Here, we propose a novel bioactive nanoconjugate of drug-loaded liposomes and bacteriophages for targeted eradication of the MDR biofilms in orthopedic infections. Phage Sb-1, which has the ability to degrade EPS, was conjugated with antibiotic-loaded liposomes. Upon encountering the biofilm, phage Sb-1 degrades the EPS structure, thereby increasing the sensitivity of bacteria to antibiotics and allowing the antibiotics to penetrate deeply into the biofilm. As a result, effective removal of MDR bacterial biofilm was achieved with low dose of antibiotics, which was proved in this study by both in vitro and in vivo investigations. Notably, in the rat prosthetic joint infection (PJI) model, we found that the liposome-phage nanoconjugates could effectively decrease the bacterial load in the infected area and significantly promote osteomyelitis recovery. It is therefore believed that the conjugation of bacteriophage and liposomes could open new possibilities for the treatment of orthopedic infections, possibly other infections in the deep tissues.

Surface engineering-based S, N co-doped biochar for improved anaerobic digestion: Enhancing microbial-pollutant and inter-microbial electron transfer synergistic EPS protection

Enhancing extracellular electron transfer (EET) efficiency is crucial for improving the anaerobic digestion (AD) system's capability to treat recalcitrant wastewater. In this study, a novel S, N co-doped biochar (S-N-BC) was prepared through surface engineering to optimize EET within AD systems. The addition of S-N-BC significantly enhanced the performance of a mesophilic AD system treating Congo red wastewater, increasing the decolorization rate by 78%, COD degradation rate by 82%, and methane yield by 87% compared to the control. Additionally, the shock resistance of anaerobic granular sludge was improved, as evidenced by the formation of the protective extracellular polymeric substances (EPS) barrier and the enhanced activities of the electron transport system. Mechanistic analysis revealed that adding S-N-BC did not alter the Congo red decolorization pathway but significantly enriched various electrochemically active bacteria and established EET pathways between microbial-pollutant and inter-microbial. This significantly accelerated EET efficiency within the AD system, ensuring stable and efficient operation under challenging conditions. This study proposed a novel approach using S-N-BC to simultaneously enhance "dual-pathway EET" between microbial-pollutant and inter-microbial while constructing an EPS protective barrier, addressing the issues of low efficiency and fragile stability of AD systems for treating recalcitrant wastewater.

Mechanism of chlorobenzene removal in biotrickling filter enhanced by non-thermal plasma: Insights from biodiversity and functional gene perspectives

Biotrickling filter (BTF) technology is inefficient in the treatment of Cl-containing volatile organic compounds (VOCs) such as chlorobenzene (CB). This study adopted non-thermal plasma (NTP) as a pretreatment and conducted in-depth analyses, especially in microorganisms, to investigate strengthening mechanism of a NTP to a BTF in the process. The introduction of NTP enhance efficiency of CB removal from 65 % to 90 %, and CO2 generation from 60 % to 85 %. It is found that the protein content of the extracellular polymeric substances increases from 212 × 10-3 mg·g−1 filler to 299 × 10-3 mg·g−1 filler, thus CB capturing and utilization enhanced. Metagenomic analysis showed that bacteria with CB-degrading properties were enriched in BTF, and CB was involved in cellular metabolism as a carbon source. The presence of active substances from NTP is found to stimulate the ability of BTF treatment. The findings of this study will provide theoretical support for the application of NTP–BTF technology.