Homoserine Lactone Research Articles

Genome-guided purification of high amounts of the siderophore ornibactin and detection of potentially novel burkholdine derivatives produced by Burkholderia catarinensis 89T.

The increased availability of genome sequences has enabled the development of valuable tools for the prediction and identification of bacterial natural products. Burkholderia catarinensis 89T produces siderophores and an unknown potent antifungal metabolite. The aim of this work was to identify and purify natural products of B. catarinensis 89T through a genome-guided approach. The analysis of B. catarinensis 89T genome revealed 16 clusters putatively related to secondary metabolism and antibiotics production. Of particular note was the identification of a nonribosomal peptide synthetase (NRPS) cluster related to the production of the siderophore ornibactin, a hybrid NRPS-polyketide synthase Type 1 cluster for the production of the antifungal glycolipopeptide burkholdine, and a gene cluster encoding homoserine lactones (HSL), probably involved in the regulation of both metabolites. We were able to purify high amounts of the ornibactin derivatives D/C6 and F/C8, while also detecting the derivative B/C4 in mass spectrometry investigations. A group of metabolites with molecular masses ranging from 1188 to 1272Da could be detected in MS experiments, which we postulate to be new burkholdine analogs produced by B. catarinensis. The comparison of B. catarinensis BGCs with other Bcc members corroborates the hypothesis that this bacterium could produce new derivatives of these metabolites. Moreover, the quorum sensing metabolites C6-HSL, C8-HSL, and 3OH-C8-HSL were observed in LC-MS/MS analysis. The new species B. catarinensis is a potential source of new bioactive secondary metabolites. Our results highlight the importance of genome-guided purification and identification of metabolites of biotechnological importance.

Adaptive Evolution of Pseudomonas aeruginosa in Human Airways Shows Phenotypic Convergence Despite Diverse Patterns of Genomic Changes.

Selective forces in the environment drive bacterial adaptation to novel niches, choosing the fitter variants in the population. However, in dynamic and changing environments, the evolutionary processes controlling bacterial adaptation are difficult to monitor. Here, we follow 9 people with cystic fibrosis chronically infected with Pseudomonas aeruginosa, as a proxy for bacterial adaptation. We identify and describe the bacterial changes and evolution occurring between 15 and 35 yr of within-host evolution. We combine whole-genome sequencing, RNA sequencing, and metabolomics and compare the evolutionary trajectories directed by the adaptation of 4 different P. aeruginosa lineages to the lung. Our data suggest divergent evolution at the genomic level for most of the genes, with signs of convergent evolution with respect to the acquisition of mutations in regulatory genes, which drive the transcriptional and metabolomic program at late time of evolution. Metabolomics further confirmed convergent adaptive phenotypic evolution as documented by the reduction of the quorum-sensing molecules acyl-homoserine lactone, phenazines, and rhamnolipids (except for quinolones). The modulation of the quorum-sensing repertoire suggests that similar selective forces characterize at late times of evolution independent of the patient. Collectively, our data suggest that similar environments and similar P. aeruginosa populations in the patients at prolonged time of infection are associated with an overall reduction of virulence-associated features and phenotypic convergence.

Application of Rosette Quorum Sensing Inhibitor in Fish Preservation

This study screened fish derived spoilage bacteria as the research object, and a development approach was used to determine the inhibitory effect of rose polyphenols on the secretion of the quorum sensing (QS) signal molecule N-acyl homoserine lactone (AHLs) by fish spoilage bacteria. The effect of rose QS inhibitors applied to fish preservation coatings on the putrefaction of spoilage bacteria was studied by measuring the changes in texture, pH, and thiobarbituric acid reactive substances (TBARS) during the storage process of fish. The findings demonstrated that the dominant strain causing fish spoilage was Sphingomonaspaucimobilis, and rose polyphenols could significantly inhibit the ability of the spoilage bacteria to secrete AHLs. The application of different concentrations (1 and 2 mg/mL) of rose polyphenols in fish preservation coatings can slow down the growth of TBARS, and 2 mg/mL of rose polyphenols has a better inhibitory effect on the oxidation of fish fat, By measuring the L*, a*, and b* values of different treatment groups, it was found that the addition of rose polyphenols delayed the decrease of L* and the increase of a* value in fish meat, but had no significant effect on b* value, The 2 mg/mL rose polyphenol coating treatment group had the slightest pH change, according on tracking measurements of pH changes during fish storage. The sensory assessment results of fish meat from different treatment groups during storage showed that the 2 mg/mL rose polyphenol treatment group decreased the least among all treatment groups, which means applying it to the fish meat preservation coating can effectively delay the rate of quality decline during storage. The findings of this work may serve as a theoretical foundation for the use of naturally occurring rose polyphenols, a QS inhibitor, in the preservation of fish.

Soybean-mediated suppression of BjaI/BjaR1 quorum sensing in Bradyrhizobium diazoefficiens impacts symbiotic nitrogen fixation.

The acyl-homoserine lactones (AHLs)-mediated LuxI/LuxR quorum sensing (QS) system orchestrates diverse bacterial behaviors in response to changes in population density. The role of the BjaI/BjaR1 QS system in Bradyrhizobium diazoefficiens USDA 110, which shares homology with LuxI/LuxR, remains elusive during symbiotic interaction with soybean. Here this genetic system in wild-type (WT) bacteria residing inside nodules exhibited significantly reduced activity compared to free-living cells, potentially attributed to soybean-mediated suppression. The deletion mutant strain ΔbjaR1 showed significantly enhanced nodulation induction and nitrogen fixation ability. Nevertheless, its ultimate symbiotic outcome (plant dry weight) in soybeans was compromised. Furthermore, comparative analysis of the transcriptome, proteome, and promoter activity revealed that the inactivation of BjaR1 systematically activated and inhibited genomic modules associated with nodulation and nitrogen metabolism. The former appeared to be linked to a significant decrease in the expression of NodD2, a key cell-density-dependent repressor of nodulation genes, while the latter conferred bacterial growth and nitrogen fixation insensitivity to environmental nitrogen. In addition, BjaR1 exerted a positive influence on the transcription of multiple genes involved in a so-called central intermediate metabolism within the nodule. In conclusion, our findings highlight the crucial role of the BjaI/BjaR1 QS circuit in positively regulating bacterial nitrogen metabolism and emphasize the significance of the soybean-mediated suppression of this genetic system for promoting efficient symbiotic nitrogen fixation by B. diazoefficiens.IMPORTANCEThe present study demonstrates, for the first time, that the BjaI/BjaR1 QS system of Bradyrhizobium diazoefficiens has a significant impact on its nodulation and nitrogen fixation capability in soybean by positively regulating NodD2 expression and bacterial nitrogen metabolism. Moreover, it provides novel insights into the importance of suppressing the activity of this QS circuit by the soybean host plant in establishing an efficient mutual relationship between the two symbiotic partners. This research expands our understanding of legumes' role in modulating symbiotic nitrogen fixation through rhizobial QS-mediated metabolic functioning, thereby deepening our comprehension of symbiotic coevolution theory. In addition, these findings may hold great promise for developing quorum quenching technology in agriculture.

The atypical organization of the luxI/R family genes in AHL-driven quorum-sensing circuits.

Quorum sensing (QS) is an elaborate regulatory mechanism associated with virulence and bacterial adaptation to the changing environment. QS is widespread in Proteobacteria and acts primarily through N-acylhomoserine lactone (AHL) signals. At the core of the AHL-driven QS systems are the AHL synthase gene (luxI family) and its cognate transcriptional regulator gene (luxR family). Several QS systems display one or more genes intervening between the luxI and luxR, in which gene arrangements are notably different due to the relative position and the transcriptional orientation between the essential luxI/R and the genes of location correlation. These adjacent genes may exert a regulatory impact on the primary QS genes or contribute toward an extension of QS regulatory control. In this review, we describe the organization of AHL-driven QS genes based on previous research and specific genome databases and provide new insights into these atypical QS gene arrangements.

A widespread methylotroph acyl-homoserine lactone synthase produces a new quorum sensing signal that regulates swarming in Methylobacterium fujisawaense.

Bacteria known as pink-pigmented facultative methylotrophs colonize many diverse environments on earth, play an important role in the carbon cycle, and in some cases promote plant growth. However, little is known about how these organisms interact with each other and their environment. In this work, we identify one of the chemical signals commonly used by these bacteria and discover that this signal controls swarming motility in the pink-pigmented facultative methylotroph Methylobacterium fujisawaense DSM5686. This work provides new molecular details about interactions between these important bacteria and will help scientists predict these interactions and the group behaviors they regulate from genomic sequencing information.

Methanogenic partner influences cell aggregation and signalling of Syntrophobacterium fumaroxidans

For several decades, the formation of microbial self-aggregates, known as granules, has been extensively documented in the context of anaerobic digestion. However, current understanding of the underlying microbial-associated mechanisms responsible for this phenomenon remains limited. This study examined morphological and biochemical changes associated with cell aggregation in model co-cultures of the syntrophic propionate oxidizing bacterium Syntrophobacterium fumaroxidans and hydrogenotrophic methanogens, Methanospirillum hungatei or Methanobacterium formicicum. Formerly, we observed that when syntrophs grow for long periods with methanogens, cultures tend to form aggregates visible to the eye. In this study, we maintained syntrophic co-cultures of S. fumaroxidans with either M. hungatei or M. formicicum for a year in a fed-batch growth mode to stimulate aggregation. Millimeter-scale aggregates were observed in both co-cultures within the first 5 months of cultivation. In addition, we detected quorum sensing molecules, specifically N-acyl homoserine lactones, in co-culture supernatants preceding the formation of macro-aggregates (with diameter of more than 20 μm). Comparative transcriptomics revealed higher expression of genes related to signal transduction, polysaccharide secretion and metal transporters in the late-aggregation state co-cultures, compared to the initial ones. This is the first study to report in detail both biochemical and physiological changes associated with the aggregate formation in syntrophic methanogenic co-cultures.Keypoints• Syntrophic co-cultures formed mm-scale aggregates within 5 months of fed-batch cultivation.• N-acyl homoserine lactones were detected during the formation of aggregates.• Aggregated co-cultures exhibited upregulated expression of adhesins- and polysaccharide-associated genes.Graphical abstract

Comprehensive computational investigation for ligand recognition and binding dynamics of SdiA: a degenerate LuxR -type receptor in Klebsiella pneumoniae.

SdiA is a LuxR-type receptor that controls the virulence of Klebsiella pneumoniae, a Gram-negative bacterium that causes various infections in humans. SdiA senses exogenous acyl-homoserine lactones (AHLs) and autoinducer-2 (AI-2), two types of quorum sensing signals produced by other bacterial species. However, the molecular details of how SdiA recognizes and binds to different ligands and how this affects its function and regulation in K. pneumoniae still need to be better understood. This study uses computational methods to explore the protein-ligand binding dynamics of SdiA with 11 AHLs and 2 AI-2 ligands. The 3D structure of SdiA was predicted through homology modeling, followed by molecular docking with AHLs and AI-2 ligands. Binding affinities were quantified using MM-GBSA, and complex stability was assessed via Molecular Dynamics (MD) simulations. Results demonstrated that SdiA in Klebsiella pneumoniae exhibits a degenerate binding nature, capable of interacting with multiple AHLs and AI-2. Specific ligands, namely C10-HSL, C8-HSL, 3-oxo-C8-HSL, and 3-oxo-C10-HSL, were found to have high binding affinities and formed critical hydrogen bonds with key amino acid residues of SdiA. This finding aligns with the observed preference of SdiA for AHLs having 8 to 10 carbon-length acyl chains and lacking hydroxyl groups. In contrast, THMF and HMF demonstrated poor binding properties. Furthermore, AI-2 exhibited a low affinity, corroborating the inference that SdiA is not the primary receptor for AI-2 in K. pneumoniae. These findings provide insights into the protein-ligand binding dynamics of SdiA and its role in quorum sensing and virulence of K. pneumoniae.

Network analysis uncovers the master role of WRKY transcription factors in Arabidopsis thaliana response to N-acyl homoserine lactones

BackgroundPlants can perceive bacterial molecules such as the quorum sensing signals N-acyl homoserine lactones (AHL), thus modifying their fitness in response to environmental factors. Even though the benefits conferred by AHL depend on various hormone signaling pathways, the understanding of AHL signaling, especially the response to AHL presence, remains largely unknown.MethodsWeighted gene co-expression network analysis (WGCNA), multi-omics network analysis, and reverse transcription quantitative PCR (RT-qPCR) assays were used to identify key genes in AHL signaling.ResultsTo obtain comprehensive insights on AHL signaling, we integrated available transcriptome data from Arabidopsis thaliana exposed to different single or multiple AHL molecules and performed a weighted gene co-expression network analysis. We identified several key genes regulated in plants exposed to multiple AHL molecules. Multi-omics network analysis and RT-qPCR assay revealed a potential role of WRKY transcription factors.ConclusionsResults presented here offer good indications for exploring the mechanism of plants' response to bacterial signaling molecules, which could further support the application of AHL-producing bacteria in sustainable agriculture.

N- acyl homoserine lactones (AHLs) type signal molecules produced by rhizobacteria associated with plants that growing in a metal(oids) contaminated soil: A catalyst for plant growth

The present study explores the potential of rhizobacteria isolated from Baccharis linearis and Solidago chilensis in metal(loid)-contaminated soil for producing N-acyl-homoserine lactones (AHLs)-type signal molecules and promoting plant growth. A total of 42 strains were isolated, four demonstrating the production of AHL-type signal molecules. Based on 16S rRNA gene sequencing analyses and MALDI-TOF analyses, these four isolates were identified as belonging to the Pseudomonas genus, specifically P. brassicacearum, P. frederickberguensis, P. koreensis, and P. orientalis. The four AHL-producing strains were evaluated for metal(loid)s tolerance, their plant growth promotion traits, AHL quantification, and their impact on in vitro Lactuca sativa plant growth.The study found that four strains exhibited high tolerance to metal(loid)s, particularly As, Cu, and Zn. Additionally, plant growth-promoting traits were detected in AHL-producing bacteria, such as siderophore production, ammonia production, ACC deaminase activity, and P solubilization. Notably, AHL production varied among strains isolated from B. linearis, where C7-HSL and C9-HSL signal molecules were detected, and S. chilensis, where only C7-HSL signal molecules were observed. In the presence of copper, the production of C7-HSL and C9-HSL significantly decreased in B. linearis isolates, while in S. chilensis isolates, C7-HSL production was inhibited. Further, when these strains were inoculated on lettuce seeds and in vitro plants, a significant increase in germination and plant growth was observed. Mainly, the inoculation of P. brassicacearum and P. frederickberguensis led to extensive root hair development, significantly increasing length and root dry weight.Our results demonstrate that rhizospheric strains produce AHL molecules and stimulate plant growth, primarily through root development. However, the presence of copper reduces the production of these molecules, potentially affecting the root development of non-metalloid tolerant plants such as S. chilensis, which would explain its low population in this hostile environment.

Identifying LasR Quorum Sensors with Improved Signal Specificity by Mapping the Sequence-Function Landscape.

Programmable intercellular signaling using components of naturally occurring quorum sensing can allow for coordinated functions to be engineered in microbial consortia. LuxR-type transcriptional regulators are widely used for this purpose and are activated by homoserine lactone (HSL) signals. However, they often suffer from imperfect molecular discrimination of structurally similar HSLs, causing misregulation within engineered consortia containing multiple HSL signals. Here, we studied one such example, the regulator LasR from Pseudomonas aeruginosa. We elucidated its sequence-function relationship for ligand specificity using targeted protein engineering and multiplexed high-throughput biosensor screening. A pooled combinatorial saturation mutagenesis library (9,486 LasR DNA sequences) was created by mutating six residues in LasR's β5 sheet with single, double, or triple amino acid substitutions. Sort-seq assays were performed in parallel using cognate and noncognate HSLs to quantify each corresponding sensor's response to each HSL signal, which identified hundreds of highly specific variants. Sensor variants identified were individually assayed and exhibited up to 60.6-fold (p = 0.0013) improved relative activation by the cognate signal compared to the wildtype. Interestingly, we uncovered prevalent mutational epistasis and previously unidentified residues contributing to signal specificity. The resulting sensors with negligible signal crosstalk could be broadly applied to engineer bacteria consortia.

Communication mediated interaction between bacteria and microalgae advances photogranulation

Recently, photogranules composed of bacteria and microalgae for carbon-negative nitrogen removal receive extensive attention worldwide, yet which type of bacteria is helpful for rapid formation of photogranules and whether they depend on signaling communication remain elusive. Varied signaling communication was analyzed using metagenomic method among bacteria and microalgae in via of two types of experimentally verified signaling molecule from bacteria to microalgae, which include indole-3-acetic acid (IAA) and N-acyl homoserine lactones (AHLs) during the operation of photo-bioreactors. Signaling communication is helpful for the adaptability of bacteria to survive with algae. Compared with non-signaling bacteria, signaling bacteria more easily adapt to the varied conditions, evidenced by the increased abundance in the operated reactors. Signaling bacteria are easier to enter the phycosphere, and they dominate the interactions between bacteria and algae rather than non-signaling bacteria. The co-abundance groups (CAGs) with signaling bacteria possess higher abundance than that without signaling bacteria (22.27 % and 6.67 %). Importantly, signaling bacteria accessibly interact with microalgae, which possess higher degree centralities and 32.50 % of them are keystone nodes in the network, in contrast to only 18.66 % of non-signaling bacteria. Thauera carrying both IAA and AHLs synthase genes are highly enriched and positively correlated with nitrogen removal rate. Our work not only highlights the essential roles of signaling communication between microalgae and bacteria in the development of photogranules, but also enriches our understanding of microbial sociobiology.

Acyl homoserine lactone-based regulation strategy for improved methane production in anaerobic digestion of agricultural wastes

The acyl homoserine lactone (AHL)-based regulation strategy presents a considerable potential in improving anaerobic digestion (AD) efficiency of complex substrates. However, the reinforcement mechanisms are still unclear. In this study, the effects of different AHL types (C4-HSL, C7-HSL, C12-HSL) and different adding times (0 d, 5 d, 15 d) on AD performance of agricultural wastes (corn straw and cattle manure) were investigated. The results indicated that all types of AHLs exerted positive effects on AD, and the adding time rather than the AHL type was the key factor affecting AD processes. The C12-5d group obtained the highest accumulated methane production (310.7 ± 2.56 mL/g VS), which increased by 47.71% than that of the Control group. The exogenous AHLs facilitated the hydrolysis and acidification of complex substrates and the utilization of released low-molecular-weight organic acids in AD systems. Furthermore, the role of methanogenic archaea was upregulated and the dominance of bacteria was relatively weakened in AD systems, which favored the establishment of their balanced and symbiotic metabolic relationship. The enriched Methanobacterium strengthened the hydrogenotrophic methanogenesis pathway. This study provides new insights into the regulation strategy of AD for agricultural waste treatment based on AHL addition.

Antibacterial and Anti-Quorum Sensing Properties of Silver Nanoparticles Phytosynthesized Using Embelia ruminata.

The rise in antibiotic resistance (AR) poses an imminent threat to human health. Nanotechnology, together with mechanisms such as quorum sensing (QS), which relies on communication between bacterial cells, may decrease the selective pressure for AR. Thus, this study aimed to investigate the effectiveness of silver nanoparticles (AgNPs) synthesized at room temperature (Rt) and 80 °C using Embelia ruminata leaf, stem-bark, and fruit extracts as antibacterial and anti-QS agents. The phytosynthesized AgNPs solutions were subjected to various characterization assays and assessed for their antibacterial activities. Quantitative QS assays were performed using Chromobacterium subtsugae CV017 and Chromobacterium violaceum ATCC 12472. Synthesized AgNPs were spherical-to-near-spherical in shape, poly-dispersed, and crystalline, with a size range of 21.06-32.15 nm. Fruit AgNPs showed stronger antibacterial activity than AgNPs from other plant organs against selected bacterial strains. In the QS assays, fruit 80 °C AgNPs demonstrated the most significant violacein inhibition in an assay performed using the short-chain acyl homoserine lactone CV017 biosensor, while the leaf and fruit Rt AgNPs demonstrated the most violacein inhibition in an assay performed using the long-chain acyl homoserine lactone ATCC 12472 biosensor. The investigations carried out in this study lay the groundwork for future innovative research into antibacterial and anti-QS strategies using E. ruminata.

N-acyl homoserine lactones lactonase est816 suppresses biofilm formation and periodontitis in rats mediated by Aggregatibacter actinomycetemcomitans

ABSTRACT Aims The current study aimed to explore the adjuvant therapeutic effect of N-acyl homoserine lactones (AHLs)-lactonase est816 on Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) biological behaviors and periodontitis progression. Methods The inhibitory properties of est816 were detected by live/dead bacterial staining, scanning electron microscope (SEM), crystal-violet staining and reverse-transcription quantitative PCR (RT-qPCR). Biocompatibility of est816 on human gingival fibroblasts (HGFs) and human gingival epithelial cells (HGEs) was evaluated by CCK8 and ELISA. The ligature-induced periodontitis model was established in rats. Micro computed tomography and immunohistochemical and histological staining served to evaluate the effect of est816 on the prevention of periodontitis in vivo. Results est816 significantly attenuated biofilm formation, reduced the mRNA expression of cytolethal distending toxin, leukotoxin and poly-N-acetyl glucosamine (PNAG) and downregulated expressions of interleukin-6 and tumor necrosis factor-α with low cell toxicity. In vivo investigations revealed est816 decreased alveolar bone resorption, suppressed matrix metalloproteinase-9 expression and increased osteoprotegerin expression. Conclusion est816 inhibited A. actinomycetemcomitans biofilm formation and virulence release, resulting in anti-inflammation and soothing of periodontitis in rats, indicating that est816 could be investigated in further research on periodontal diseases.

Catechol-type siderophore producer Streptomyces spp. with quorum-quenching activity isolated from wild medicinal plants rhizosphere

Traditional medicinal plants represent a unique source for the isolation of Streptomycetes and antimicrobial compounds. Antimicrobial activity of Streptomyces isolates collected from the rhizosphere of different native medicinal plants in Iran, was investigated against Gram-positive and Gram-negative bacteria. Multi-omics analysis was performed to identify active compounds corresponding to the observed bioactivities. Since cell-to-cell communication mediated by N-acyl homoserine lactones (AHLs) is important for the virulence of Gram-negative pathogenic bacteria, quorum quenching activity of the isolates and their ability to degrade C6-HSL and C8-HSL were tested. Two highly related Streptomyces isolates derived from the Helichrysum rubicundum and Rumex acetosa rhizosphere, respectively, exhibited bioactivity against pathogenic indicator bacteria. Metabolite analysis of extracts obtained from liquid cultures of both isolates revealed the production of the catechol-peptide siderophores streptobactin and tribenarthin. Proteomic analysis confirmed the presence of proteins encoded by the streptobactin and lidamycin biosynthetic gene clusters. Quorum quenching activity of the strains and AHL-degrading enzyme production was confirmed using a GFP producing biosensor and LC-MS analysis. This study demonstrates catecholate siderophore production and QQ potential of two Streptomyces isolates from medicinal plants rhizosphere from Mishan Plain, Hamedan Province, Iran using metabolomics and proteomics analysis. Production of streptobactin by terrestrial Streptomyces sp. strains was confirmed for the first time.

The quorum sensing molecule C12-HSL promotes biofilm formation and increases adrA expression in Salmonella Enteritidis under anaerobic conditions

Acyl-homoserine lactones (AHLs) are quorum-sensing signaling molecules in Gram-negative bacteria and positively regulate biofilm formation in Salmonella under specific conditions. In this study, biofilm formation in Salmonella enterica was evaluated at 28 and 37 °C, under aerobic and anaerobic conditions. Additionally, the influence of the N-dodecanoyl-DL-homoserine lactone (C12-HSL) on biofilm formation and the expression of genes related to the synthesis of structural components, regulation, and quorum sensing was assessed under anaerobiosis at 28 and 37 °C. Biofilm formation was found not to be influenced by the atmospheric conditions at 28 °C. However, it was reduced at 37 °C under anaerobiosis. C12-HSL enhanced biofilm formation at 37 °C under anaerobiosis and increased the expression of the adrA and luxS genes, suggesting an increase in c-di-GMP, a second messenger that controls essential physiological functions in bacteria. These results provide new insights into the regulation of biofilm formation in Salmonella under anaerobic conditions.

Inhibition of Quorum Sensing to Mitigate the Risks of Membrane Biofouling in Biological Wastewater Treatment

Membrane-based systems play a pivotal role in various applications, providing efficient separation, purification, and filtration processes across diverse industries such as water purification and desalination. However, this system faces major challenge of membrane biofouling impacting the efficiency and sustainability of such systems. Biofouling occurs when various microorganisms like bacteria, fungi, etc. adheres to the surface of membrane and form biofilm which results in reducing membrane permeability and increasing its operational cost. Various physical, chemical and biological strategies are known to prevent biofouling. Inhibition of quorum sensing is a recent trend based on the researches that shows quorum sensing as an integral part of biofilm formation. Bacteria’s uses cell to cell communication mechanisms known as Quorum sensing, plays an important role in formation of virulence factors, biofilm. It is regulated by quorum sensing signalling molecules known as autoinducers like Autoinducing peptides, acyl homoserine lactones, Autoinducer-2. Various strategies can be adopted to inhibit quorum sensing: inhibition of Autoinducer synthase which is responsible for synthesizing autoinducers; inhibition/degradation of autoinducers and interfering with signal receptors. This article provides deeper knowledge of Quorum sensing (QS), methods of QS inhibition: Quorum quenching which involves the enzymatic degradation of QS signaling molecules, and the use of Quorum sensing inhibitor compounds in preventing membrane biofouling are discussed in detail. This article delves into the potential of disrupting quorum sensing pathways to prevent or reduce biofilm formation, thereby enhancing the performance and longevity of membranes in wastewater treatment. The mitigation of biofouling can revolutionize membrane-based systems, ensuring their sustainability and efficacy in water treatment processes

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.

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.