Quorum Quenching Research Articles

Isolation and application of Bacillus thuringiensis LZX01: Efficient membrane biofouling mitigation function and anti-toxicity potential

Significant progress has been made in mitigating membrane biofouling by microbial quorum quenching (QQ). More efficient and survivable QQ strains need to be discovered. A new strain named Bacillus thuringiensis LZX01 was isolated in this study using a low carbon source concentration “starving” method from a membrane bioreactor (MBR). LZX01 secreted intracellular lactonase to enable QQ behavior and was capable of degrading 90 % of C8-HSL (200 ng/mL) within 30 min, which effectively delayed biofouling by inhibiting the growth of bacteria associated with biofouling and improving the hydrophilicity of bound extracellular polymeric substances. As a result, the membrane biofouling rate of MBR adding LZX01 was four times slower than that of the control MBR. Importantly, LZX01 maintains its QQ activity even in environments contaminated with typical toxic pollutants. Therefore, with high efficiency, toxicity resistance, and easy culture, LZX01 holds great potential and significant promise for biofouling control applications.

Quorum Quenching Nanofibers for Anti-Biofouling Applications

Biofilms, complex microbial communities, adept at forming on diverse surfaces within environments, such as membrane technologies, ship hulls, medical devices, and clinical infections, pose persistent challenges. While various biofilm prevention methods, including antimicrobial coatings, physical barriers, and bacteriophage utilization, have been devised for engineered systems, their efficacy fluctuates based on application type and microbial species. Consequently, there remains a pressing need for the development of highly targeted and efficient biofilm control strategies tailored to specific applications remains a pressing need. In our investigation, we disrupt microbial cell-to-cell communication in Pseudomonas aeruginosa through the application of anti-quorum sensing (anti-QS) furanone C-30 molecules. The incorporation of these molecules onto electrospun surfaces yielded substantial reductions of 69% in petri dish assays and 58% on mixed cellulose ester (MCE) membranes in a dead-end nanofiltration system, showcasing the potent anti-biofouling impact. Notably, the functionalization of MCE surfaces with anti-QS molecules resulted in a remarkable 16.7% improvement in filtration output. These findings underscore the potential of this targeted approach to mitigate biofilm formation, offering a technical foundation for advancing tailored strategies in the ongoing pursuit of effective and application-specific biofilm control measures.

Quorum quenching activity of endophytic Bacillus sp. EBS9 from Tecomella undulata and its biocontrol applications

This study investigates the quorum quenching (QQ) activity of an endophytic bacterium, Bacillus sp. EBS9, isolated from the native medicinal plant Tecomella undulata of Rajasthan, and its biocontrol potential against the soft rot pathogen Pectobacterium carotovorum subsp. carotovorum (Pcc). QQ activity was confirmed by the loss of violacein pigment in Chromobacterium violaceum (MCC 2290). Quorum quenching metabolites were extracted using ethyl acetate, and the Quorum Quenching Extract (QQE) demonstrated positive activity in assays with C. violaceum CV026 (MCC 2216). HRLC-MS analysis identified diketopiperazines, L,L-Cyclo (leucylprolyl) and Cyclo (L-Phe-L-Pro), which are N-acyl homoserine lactones (AHLs) antagonists competing for LuxR receptor binding sites. In vitro and in planta assays evaluated QQB's biocontrol potential using treatment I (Pcc), treatment II (Pcc + QQB), and a control (sterile water). In the in vitro soft rot attenuation assay showed that treatment I caused severe maceration in vegetable slices, particularly in radish, exhibiting the highest maceration diameter (25.33 ± 3.52 mm) and percentage (46.14 ± 5.70 %). However, co-inoculation with QQB significantly reduced maceration across all tested vegetables. In the plate assay, germination rates decreased to approximately 50 % in both Vigna radiata and Raphanus sativus for treatment I, but improved to 86.67 % in treatment II. The seed vigour and germination indices also improved with QQB treatment in both plant species. In the pot assay after 30 days, in contrast to a 50 % decrease in root and shoot lengths in treatment I, treatment II led to a substantial recovery, with root lengths increase by 112.07 % and 138.76 %, while shoot length by 315.65 % and 163.63 % in V. radiata and R. sativus, respectively. This study highlights the QQ and biocontrol potential of Bacillus sp. EBS9 against P. carotovorum (Pcc), suggesting its promise in effective management of phytopathogens, which is crucial for agricultural productivity while minimizing environmental impact.

Quorum sensing and its inhibition mechanisms

The article is a brief literature review. This article provides an overview of the Quorum Sensing system in bacterial communities, highlighting the peculiarities of the system for gram-positive and gramnegative microorganisms. Basic information about the three existing Quorum Sensing systems is presented. Information is also given about different types of autoinducers, which are signaling molecules that trigger a cascade of behavioral reactions. The importance of the Quorum Sensing system as one of the fundamental mechanisms in the formation and regulation of bacterial biofilms is described, emphasizing the significance of biofilm microorganisms for modern clinical medicine and their impact on aggravating the issue of antibiotic resistance. The main mechanisms of inhibiting bacterial quorum, including by other microorganisms, are presented. The work discusses enzymatic and non-enzymatic methods of inhibiting the Quorum Sensing system, points of application and mechanisms of action. Some microorganisms with confirmed enzymatic activity by Quorum Quenching are indicated. Also presented are registered cases of suppression of other bacteria by microorganisms through the Quorum Sensing inhibitors system.

Application of psychrotolerant quorum quenching Planococcus versutus sp. L10.15T to membrane bioreactors for biofouling control at low temperatures

Planococcus versutus sp. L10.15T, a psychrotolerant quorum quenching bacterium, was effective in mitigating biofouling through the degradation of N-acyl homoserine lactones (AHLs) in membrane bioreactors at low temperatures.

Membrane reciprocation and quorum quenching: An innovative combination for fouling control and energy saving in membrane bioreactors

Membrane bioreactors (MBRs) play a crucial role in wastewater treatment, but they face considerable challenges due to fouling. To tackle this issue, innovative strategies are needed. This study investigated the effectiveness of membrane reciprocation and quorum quenching (QQ) to control fouling in MBRs. The study compared MBRs using membrane reciprocation (30 rpm) and QQ (injecting media containing 100 or 200 mg/L BH4) with conventional MBRs employing different air-scouring intensities. The results demonstrated that combining membrane reciprocation (30 rpm) with QQ (200 mg/L BH4) significantly extended the service time of MBRs, making it approximately six times longer than conventional methods. Moreover, this approach reduced physically reversible resistance. The reduction in signal molecules related to biofouling due to QQ showcased its critical role in controlling biofouling, even under high shear caused by membrane reciprocation. However, the impact of QQ on microbial community structure appeared relatively insignificant when compared to factors such as operation time, aeration intensity, and membrane reciprocation. By combining membrane reciprocation and QQ, the study achieved a remarkable 81 % energy saving compared to extensive aeration (103 s−1 in velocity gradient), in addition to the extended service time. Importantly, this combined antifouling approach did not negatively affect microbial characteristics and wastewater treatment, emphasizing its effectiveness in MBRs. Overall, the findings of this study offer valuable insights for developing synergistic fouling control strategies in MBRs, significantly improving the energy efficiency of the wastewater treatment process.

Inhibition of quorum sensing serves as an effective strategy to mitigate the risks of human bacterial pathogens in soil

The coexistence of antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and virulence factor genes (VFGs) in human bacterial pathogens (HBPs) increases their risks to ecological security and human health and no effective strategy is available. Herein, we demonstrated two typical quorum sensing (QS) interfering agents, 4-nitropyridine-N-oxide (4-NPO, a QS inhibitor) and Acylase Ⅰ (a quorum quenching (QQ) enzyme), effectively decreased the abundance of HBPs by 48.30% and 72.54%, respectively, which was accompanied by the reduction of VFGs, ARGs, and MGEs. The decrease in QS signals mediated by QS interfering agents disturbed bacterial communication and inhibited biofilm formation. More importantly, QS interfering agents reduced the intra-species and inter-species conjugation frequencies among bacteria, considerably inhibiting the dissemination of ARGs and VFGs via horizontal gene transfer. Furthermore, the QS interfering agents did not significantly affect the metabolic function of other nonpathogenic microorganisms in the soil. Collectively, our study provides an effective and eco-friendly strategy to mitigate the risks of HBPs in soil.

Quorum Quenching with a Diffusible Signal Factor Analog in Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia is a multidrug-resistant Gram-negative bacillus associated with nosocomial infections in intensive care units, and nowadays, its acquired resistance to trimethoprim-sulfamethoxazole (SXT) by sul genes within class 1 integrons is a worldwide health problem. Biofilm and motility are two of the major virulence factors in this bacterium and are auto-induced by the diffusible signal factor (DSF). In recent studies, retinoids have been used to inhibit (Quorum Quenching) these virulence factors and for their antimicrobial effect. The aim was to reduce biofilm formation and motility with retinoic acid (RA) in S. maltophilia SXT-resistant strains. Eleven SXT-resistant strains and two SXT-susceptible strains were tested for biofilm formation/reduction and planktonic/sessile cell viability with RA and SXT-MIC50/RA; motility (twitching, swimming, swarming) was measured with/without RA; and MLST typing was determined. The biofilm formation of the strains was classified as follows: 15.38% (2/13) as low, 61.54% (8/13) as moderate, and 23.08% (3/13) as high. It was significantly reduced with RA and SXT-MIC50/RA (p < 0.05); cell viability was not significantly reduced with RA (p > 0.05), but it was with SXT-MIC50/RA (p < 0.05); and swimming (p < 0.05) and swarming (p < 0.05) decreased significantly. MLST typing showed the first and novel strains of Mexican S. maltophilia registered in PubMLST (ST479-485, ST497, ST23, ST122, ST175, ST212, and ST300). In conclusion, RA reduced biofilm formation and motility without affecting cell viability; furthermore, antimicrobial synergism with SXT-MIC50/RA in different and novel STs of S. maltophilia was observed.

Bacterial biofilm formation and anti-biofilm strategies

Bacteria are ubiquitous prokaryotes. They are involved in biofilm formation and also have the ability to produce anti-biofilm products for biofilm mitigation. This special issue entitled: “Biofilms- community structure, applications and mitigation” of the journal Research in Microbiology was designed to discuss the flexibility of bacterial biofilms and their products under particular circumstances. Given that quorum sensing (QS) controls biofilm growth in some situations, especially for pathogenic bacteria antibiotic evading strategies. In Gram-negative bacteria, N-acyl homoserine lactones are the major quorum sensing signaling molecules. Another approach to prevent bacterial biofilm formation may be to inhibit the QS-regulated activities using quorum quenching (QQ). In this context, QS inhibitors and QS enzymes are important because they, respectively, interfere with signal creation, perception, or degradation and chemical modification. There have been numerous reports of QQ enzymes from bacteria. Treatment failure and recurrent staphylococcal infections are also brought on by biofilm development, which boosts an organism's ability to withstand antibiotics and is thought to be a virulence factor in patients. However, polyphenol quercetin antibiofilm activity is naturally available against drug-resistant Staphylococcus aureus.

Repurposing albendazole as a potent inhibitor of quorum sensing-regulated virulence factors in Pseudomonas aeruginosa: Novel prospects of a classical drug

Pseudomonas aeruginosa has emerged as a critical superbug that poses a serious threat to public health. Owing to its virulence and multidrug resistance profiles, the pathogen demands immediate attention for devising alternate intervention strategies. In an attempt to repurpose drugs against P. aeruginosa, this preclinical study was aimed at investigating the antivirulence prospects of albendazole (AbZ), an FDA-approved anti-helminthic drug, recently predicted to disrupt quorum sensing (QS) in Chromobacterium violaceum. AbZ was scrutinized for its quorum quenching (QQ) prospects, effect on bacterial virulence, different motility phenotypes, and biofilm formation in vitro. Additionally, in silico analysis was employed to predict the molecular interactions between AbZ and QS receptors. At sub-inhibitory levels, AbZ demonstrated anti-QS activity and significantly abrogated AHL biosynthesis in P. aeruginosa. Moreover, AbZ significantly downregulated the transcript levels of QS- (lasI/lasR, rhlI/rhlR, and pqsA/pqsR) and QS-dependent virulence (aprA, lasA, lasB, plcH, and toxA) genes in P. aeruginosa. This coincided with reduced hemolysin, alginate, pyocyanin, rhamnolipids, total protease, and elastase production, thereby lowering phenotypic virulence. Molecular docking with AbZ further revealed strong associations and high binding energies with LasR (−8.8 kcal/mol), RhlR (−6.5 kcal/mol), and PqsR (−6.3 kcal/mol) receptors. AbZ also impeded bacterial motility and abolished EPS production, severely compromising pseudomonal biofilm formation. For the first time, AbZ was shown to interfere with QS circuitry and consequently disarming pseudomonal virulence. Hence, AbZ can be exploited for its antivirulence properties against P. aeruginosa.

Biofouling Control by Facultative Quorum Quenching Bacteria in Anaerobic Membrane Bioreactors for High-Strength Wastewater Treatment

Biofouling Control by Facultative Quorum Quenching Bacteria in Anaerobic Membrane Bioreactors for High-Strength Wastewater Treatment

High-Throughput, Quantitative Screening of Quorum-Sensing Inhibitors Based on a Bacterial Biosensor.

Quorum sensing (QS) is a cell-cell communication mechanism by which bacteria synchronize social behaviors such as biofilm formation and virulence factor secretion by producing and sensing small molecular signals. Quorum quenching (QQ) by degrading signals or blocking signal transmissions has become a promising strategy for disrupting QS and preventing bacterial infection and biofilm formation. However, studies of high-throughput screening and identification approaches for quorum-sensing inhibitors (QSIs) are still inadequate. In this work, we developed a sensitive, high-throughput approach for screening QSIs based on the bacterial biosensor strain Agrobacterium tumefaciens N5 (pBA7P), which contains a traG gene promoter induced by QS signals fused with a promoterless β-lactamase gene reporter. Using this approach, we identified 31 QQ bacteria from ∼2000 soil bacterial isolates, some belonging to the genera Bosea, Cupriavidus, and Flavobacterium that have not been reported previously as QQ bacteria. We also identified four QS inhibitory compounds and one QS signal analogue from ∼5000 small-molecule compounds, which profoundly affected the expression of QS-regulated genes and phenotypes of the pathogenic bacteria. This high-throughput screening system is effective and sensitive for screening of both QQ microbes and small molecules, enabling the discovery of a wide variety of biocompatible compounds.

Isolation of a quorum quenching bacterium effective to various acyl-homoserine lactones: Its quorum quenching mechanism and application to a membrane bioreactor

Biofouling, caused by microbial biofilm formation on the membrane surface and in pores, is a major operational problem in membrane bioreactors (MBR). Many quorum quenching (QQ) bacteria have been isolated and applied to MBR to reduce biofouling. However, for more effective MBR biofouling control, novel approaches for isolating QQ bacteria and applying them in MBR are needed. Therefore, Listeria grayi (HEMM-2) was isolated using a mixture of different N-acyl homoserine lactones (AHLs). HEMM-2 degraded various AHLs, regardless of the length and oxo group in the carbon chain, with quorum sensing (QS) inhibition ratios of 47–61%. This QQ activity was attributed to extracellular substances in HEMM-2 cell-free supernatant (CFS). Furthermore, the HEMM-2 CFS negatively regulated QS-related gene expression, inhibiting Pseudomonas aeruginosa and activated sludge-biofilm formation by 53–75%. Surprisingly, when the HEMM-2 CFS was directly injected into a laboratory-scale MBR system, biofouling was not significantly affected. Biofouling was only controlled by cell suspension (CS) of HEMM-2, indicating the importance of QQ bacteria in MBR. The HEMM-2 CS increased operation time to reach 0.4 bar, a threshold transmembrane pressure for complete biofouling, from 315 h to 371 h. Taken together, HEMM-2, which is effective in the degradation of various AHLs, and its applicable method to MBR may be considered a potent approach for controlling biofouling and understanding the behavior of QQ bacteria in MBR systems.

Biofouling mitigation of a membrane bioreactor for industrial wastewater treatment by quorum quenching

Quorum quenching (QQ) has been extensively studied in sewage treatment membrane bioreactors (MBRs) to alleviate biofouling, but its application in industrial-wastewater MBRs remains limited. This study confirmed the applicability of QQ in MBRs treating wastewater from the display manufacturing process. QQ alginate and QQ polyvinyl alcohol (PVA)/alginate beads, which entrapped Bacillus sp. SDC-U1, a QQ isolate from tetramethylammonium hydroxide (TMAH)-wastewater treatment sludge, were applied to a lab-scale MBR treating real wastewater containing TMAH, a developer used in the display manufacturing process. To immobilize pH-sensitive SDC-U1 on PVA/alginate beads, the first cross-linking solution's pH was adjusted to 5, followed by a 4 h incubation in Luria-Bertani broth to enhance the activity of SDC-U1. MBRs with QQ alginate and QQ PVA/alginate beads showed a 40 % and 365 % longer time to reach 30 kPa TMP, respectively, compared to MBRs without beads. QQ beads significantly reduced the concentration of various N-acyl homoserine lactones, which are signaling molecules involved in quorum sensing, in the MBR. The observation of biofilm on the membrane surface confirmed the biofouling mitigation by QQ application. This study demonstrates that biofouling can be effectively mitigated using appropriate QQ bacteria and their immobilization methods in industrial wastewater MBRs containing toxic substances like TMAH.

Inhibiting Biofilm Formation via Simultaneous Application of Nitric Oxide and Quorum Quenching Bacteria.

Membrane biofouling is an inevitable challenge in membrane-based water treatment systems such as membrane bioreactors. Recent studies have shown that biological approaches based on bacterial signaling can effectively control biofilm formation. Quorum quenching (QQ) is known to inhibit biofilm growth by disrupting quorum sensing (QS) signaling, while nitric oxide (NO) signaling helps to disperse biofilms. In this study, batch biofilm experiments were conducted to investigate the impact of simultaneously applying NO signaling and QQ for biofilm control using Pseudomonas aeruginosa PAO1 as a model microorganism. The NO treatment involved the injection of NONOates (NO donor compounds) into mature biofilms, while QQ was implemented by immobilizing QQ bacteria (Escherichia coli TOP10-AiiO or Rhodococcus sp. BH4) in alginate or polyvinyl alcohol/alginate beads to preserve the QQ activity. When QQ beads were applied together with (Z)-1-[N-(3-aminopropyl)-N-(n-propyl) amino]diazen-1-ium-1,2-diolate (PAPA NONOate), they achieved a 39.0% to 71.3% reduction in biofilm formation, which was substantially higher compared to their individual applications (16.0% to 54.4%). These findings highlight the significant potential of combining QQ and NO technologies for effective biofilm control across a variety of processes that require enhanced biofilm inhibition.

Whole-Cell Biosensors for Qualitative and Quantitative Analysis of Quorum Sensing Signal Molecules and the Investigation of Quorum Quenching Agents.

In Pseudomonas aeruginosa relevant features including virulence and biofilm formation are controlled by quorum sensing (QS), a cell density-dependent intercellular communication system based on the production and response to signal molecules. P. aeruginosa has evolved chemically distinct compounds employed as QS signal molecules (QSSMs) that can be detected and quantified through rapid, sensitive, and low-cost methods based on whole-cell biosensors. Here, we present a series of protocols based on whole-cell biosensors for qualitative and quantitative analysis of QSSMs produced by P. aeruginosa. These protocols can be used to investigate the impact of environmental conditions, genetic modifications, or quorum quenching agents on the production of QSSMs in P. aeruginosa.

Engineering a Pseudomonas putida as living quorum quencher for biofilm formation inhibition, benzenes degradation, and environmental risk evaluation

Bacterial communication interruption based on quorum quenching (QQ) has been proven its potential in biofilm formation inhibition and biofouling control. However, it would be more satisfying if QQ could be combined with the efficient degradation of contaminants in environmental engineering. In this study, we engineered a biofilm of Pseudomonas putida through introducing a QQ synthetic gene, which achieved both biofilm formation inhibition and efficient degradation of benzene series in wastewater. The aiiO gene introduced into the P. putida by heat shock method was highly expressed to produce QQ enzyme to degrade AHL-based signal molecules. The addition of this engineered P. putida reduced the AHLs concentration, quorum sensing gene expression, and connections of the microbial community network in activated sludge and therefore inhibited the biofilm formation. Meanwhile, the sodium benzoate degradation assay indicated an enhanced benzene series removal ability of the engineering bacteria on activated sludge. Besides, we also demonstrated a controllable environmental risk of this engineered bacteria through monitoring its abundance and horizontal gene transfer test. Overall, the results of this study suggest an alternative strategy to solve multiple environmental problems through genetic engineering means and provide support for the application of engineered bacteria in environmental biotechnology.

Interactions between quorum sensing/quorum quenching and virulence genes may affect coral health by regulating symbiotic bacterial community

Quorum sensing (QS) and quorum quenching (QQ) are two antagonistic processes that may regulate the composition, function and structure of bacterial community. In coral holobiont, autoinducers signaling mediate the communication pathways between interspecies and intraspecies bacteria, which regulate the expression of the virulence factors that can damage host health. However, under environmental stressors, the interaction between the QS/QQ gene and virulence factors and their role in the bacterial communities and coral bleaching is still not fully clear. To address this question, here, metagenomics method was used to examine the profile of QS/QQ and virulence genes from a deeply sequenced microbial database, obtained from three bleached and non-bleached corals species. The prediction of bacterial genes of bleached samples involved in functional metabolic pathways were remarkably decreased, and the bacterial community structure on bleached samples was significantly different compared to non-bleached samples. The distribution and significant difference in QS/QQ and virulence genes were also carried out. We found that Proteobacteria was dominant bacteria among all samples, and AI-1 system is widespread within this group of bacteria. The identified specific genes consistently exhibited a trend of increased pathogenicity in bleached corals relative to non-bleached corals. The abundance of pathogenicity-associated QS genes, including bapA, pfoA and dgcB genes, were significantly increased in bleached corals and can encode the protein of biofilm formation and the membrane damaging toxins promoting pathogenic adhesion and infection. Similarly, the virulence genes, such as superoxide dismutase (Mn-SOD gene), metalloproteinase (yme1, yydH and zmpB), glycosidases (malE, malF, malG, and malK) and LodAB (lodB) genes significantly increased. Conversely, QQ genes that inhibit QS activity and virulence factors to defense the pathogens, including blpA, lsrK, amiE, aprE and gmuG showed a significant decrease in bleached groups. Furthermore, the significant correlations were found among virulence, QS/QQ genes, and coral associated bacterial community, and the virulence genes interact with key QS/QQ genes, directly or indirectly influence symbiotic bacterial communities homeostasis, thereby impacting coral health. It suggested that the functional and structural divergence in the symbiont bacteria may be partially attribute to the interplay, involving interactions among the host, bacterial communication signal systems, and bacterial virulence factors. In conclusion, these data helped to reveal the characteristic behavior of coral symbiotic bacteria, and facilitated a better understanding of bleaching mechanism from a chemical ecological perspective.

A low N-acyl-homoserine lactone-degrading Stentrophomonas sp. that could efficiently mitigate biofouling in a membrane bioreactor

Quorum quenching (QQ) is a promising and sustainable strategy for mitigating membrane biofouling in membrane bioreactors (MBRs). In this study, six QQ bacterial strains were isolated, and two of them, Bacillus sp. L (strain L) and Stenotrophomonas sp.Y6 (strain Y6), were further studied. Interestingly, strain L could degrade quorum-sensing signal molecules more efficiently than strain Y6. However, strain Y6 could better mitigate membrane biofouling in MBR, reducing the TMP from 31 kPa to 10 kPa, compared with 17 kPa achieved by L at the end of a 25-day MBR operation. This might be due to the presence of extracellular QQ enzymes in Y6 and the rapid adaptation of Y6 to the conditions within the MBR. In addition, Y6 did not affect the contents of COD, NH4+-N, total nitrogen, and total phosphorus in the effluent released by the MBR. These findings may reveal a new connection between the QQ activity of the bacterial cells and their ability to mitigate biofouling, a prospect that could enable the evaluation of efficient QQ candidates for practical application in wastewater treatment.

Biofouling mitigation and microbial community dynamics in the membrane bioreactor by the indigenous quorum quenching bacterium Delftia sp. JL5

The quorum quenching (QQ) strategy has attracted increasing attention in membrane bioreactor (MBR) fouling control. However, the applicable QQ strain remains limited. This study investigated the antibiofouling performance of a new indigenous QQ bacterium, Delftia sp. JL5 (JL5) in MBR. JL5 produces intracellular acylase that irreversibly degrades N-acylhomoserine lactones (AHL), inhibited biofilm formation of quorum-sensing bacteria from activated sludge. During 120 days of operation, immobilized JL5 substantially delayed MBR biofouling by 2.1 and 2.9 times, at a flux rate of 30 L/(m2·h) and 20 L/(m2·h), respectively. A slower flux rate was favorable for effective mitigation of JL5 biofouling. JL5 reduced the AHL and extracellular polymeric substances of biocake without affecting the efficiency of waste removal. The presence of JL5 significantly changed the microbial structure of the membrane biocake, but not the activated sludge. Collectively, high activity, durability, and acid tolerance credited JL5 as a promising strain for QQ-MBR.