Deciphering quorum sensing and quorum quenching regulatory mechanisms in anaerobic digesters: Signaling networks, environmental responses, and microbial ecological functions

Quorum sensing (QS) is a chemical communication system by which bacteria coordinate gene expression and social behaviors. Quorum quenching (QQ) refers to processes of inhibiting the QS pathway. Deep-sea hydrothermal vents are extreme marine environments, where abundant and diverse microbial communities live. However, the nature of chemical communication in bacteria inhabiting the hydrothermal vent is poorly understood. In this study, the QS and QQ activities with N-acyl homoserine lactones (AHLs) as the autoinducer were detected in bacteria isolated from hydrothermal vents in the Okinawa Trough. A total of 18 and 108 isolates possessed AHL-producing and AHL-degrading abilities, respectively. Bacteria mainly affiliated with Rhodobacterales, Hyphomicrobiales, Enterobacterales and Sphingomonadales showed QS activities; QQ was mainly associated with Bacillales, Rhodospirillales and Sphingomonadales. The results showed that the bacterial QS and QQ processes are prevalent in hydrothermal environments in the Okinawa Trough. Furthermore, QS significantly affected the activities of extracellular enzymes represented by β-glucosidase, aminopeptidase and phosphatase in the four isolates with higher QS activities. Our results increase the current knowledge of the diversity of QS and QQ bacteria in extreme marine environments and shed light on the interspecific relationships to better investigate their dynamics and ecological roles in biogeochemical cycling.

Regulation and application of quorum sensing on anaerobic digestion system

Antimicrobial resistance (AMR) is a growing global concern, necessitating alternative strategies to fight bacterial infections. Bacteria use quorum sensing (QS) to regulate their virulence, biofilm formation, and resistance mechanisms. Quorum quenching (QQ) disrupts QS, reducing pathogenicity and potentially lowering the selective pressure for resistance compared to conventional antibiotics. Understanding QS and QQ mechanisms can aid in developing effective antimicrobial therapies. This review examines QS and QQ mechanisms, focusing on key signaling molecules like acyl-homoserine lactones (AHLs) and autoinducer-2 (AI-2). Various QQ agents, including enzymes and phytocompounds are discussed for their roles in disrupting bacterial communication. Phytocompounds such as curcumin, resveratrol, and quercetin have shown potential in inhibiting QS-regulated biofilms and virulence factors. QS inhibition and QQ present promising antimicrobial strategies. By targeting bacterial communication rather than growth, these approaches help mitigate resistance development. Future research should focus on optimizing QQ therapies, integrating them with antibiotics, and enhancing their clinical applications through advanced drug delivery systems to improve treatment outcomes.

Genetic insights unraveling quorum quenching potential of indigenous isolates from an anaerobic membrane bioreactor

Casuarina equisetifolia, a key species in subtropical coastal shelterbelts, faces serious challenges in sustainable plantation management due to continuous planting obstacles. This study explores how AHL-mediated quorum sensing (QS) influences these obstacles by regulating microbial dynamics in the rhizosphere of continuously planted C. equisetifolia. Results show that with increasing generations of continuous planting, the abundance of QS bacteria-especially pathogenic strains-significantly increased, with notable shifts in community composition. The number of QS isolates rose from 32 (FCP) to 68 (SCP) and 81 (TCP), with Enterobacteriaceae being the most abundant. Among 10 identified QS species, Pantoea ananatis showed the highest AHL activity, while Burkholderia lata had the lowest. Short-chain AHL (C4-HSL and C6-HSL) were most common, with P. ananatis producing the highest diversity and concentration. Pathogenicity tests indicated that seven QS bacteria damaged roots and inhibited water uptake, leading to wilting. In contrast, three Burkholderia species were non-pathogenic. Meanwhile, the abundance of quorum quenching (QQ) bacteria decreased significantly across planting generations (94, 70, to 63), and key QQ strains like Bacillus spp. showed no pathogenicity. These findings suggest that continuous planting enriches pathogenic AHL-mediated QS bacteria while reducing beneficial QQ populations, altering microbial community structure and exacerbating replant issues. This study offers important theoretical insights into the mechanisms behind continuous planting obstacles in C. equisetifolia.

The occurrence of biofouling restricts the widespread application of membrane bioreactors (MBRs) in wastewater treatment. Regulation of quorum sensing (QS) is a promising approach to control biofouling in MBRs, yet the underlying mechanisms are complex and remain to be illustrated. A fundamental understanding of the relationship between QS and membrane biofouling in MBRs is lacking, which hampers the development and application of quorum quenching (QQ) techniques in MBRs (QQMBRs). While many QQ microorganisms have been isolated thus far, critical criteria for selecting desirable QQ microorganisms are still missing. Furthermore, there are inconsistent results regarding the QQ lifecycle and the effects of QQ on the physicochemical characteristics and microbial communities of the mixed liquor and biofouling assemblages in QQMBRs, which might result in unreliable and inefficient QQ applications. This review aims to comprehensively summarize timely QQ research and highlight the important yet often ignored perspectives of QQ for biofouling control in MBRs. We consider what this "information" can and cannot tell us and explore its values in addressing specific and important questions in QQMBRs. Herein, we first examine current analytical methods of QS signals and discuss the critical roles of QS in fouling-forming microorganisms in MBRs, which are the cornerstones for the development of QQ technologies. To achieve targeting QQ strategies in MBRs, we propose the substrate specificity and degradation capability of isolated QQ microorganisms and the surface area and pore structures of QQ media as the critical criteria to select desirable functional microbes and media, respectively. To validate the biofouling retardation efficiency, we further specify the QQ effects on the physicochemical properties, microbial community composition, and succession of mixed liquor and biofouling assemblages in MBRs. Finally, we provide scale-up considerations of QQMBRs in terms of the debated QQ lifecycle, practical synergistic strategies, and the potential cost savings of MBRs. This review presents the limitations of classic QS/QQ hypotheses in MBRs, advances the understanding of the role of QS/QQ in biofouling development/retardation in MBRs, and builds a bridge between the fundamental understandings and practical applications of QQ technology.

The quest for new anti-virulence medications has been sparked by the rising antibiotic resistance rates of pathogenic bacteria. By interfering with vital components of bacteria, such as their cell walls, nucleic acids and protein biosynthesis, conventional antibiotics kill or restrict bacterial growth. This predictable selection force may lead to the rise of antibiotic-resistant microbial pathogens. Antibiotic treatment of microbial illnesses frequently results in a hostile environment in which bacteria evolve survival strategies, such as biofilm growth, which tends to result in multidrug resistance. These microorganisms typically interact with one another through a procedure known as quorum sensing (QS). By manipulating the expression of genes, particularly those determining virulence, depending on the density of bacterial cells, QS allows bacteria to interact with one another and governs the pathogenesis of many species. The pathogenic world uses the QS signalling system to determine population density and coordinate virulence gene development. Quorum quenching (QQ) was thus proposed for disease treatment and prevention by interacting with the bacterial QS system. Using QQ, it may be possible to create next-generation antibiotics that are particularly effective at preventing QS-mediated pathogenic infections by disrupting bacterial communication. This chapter gives a summary of the fundamental ideas and mechanisms of QS and discusses the application of QQ as a possible tactic in the fight against the threat of microbe pathogenicity and antibiotic resistance.

Acyl-homoserine lactone-based quorum sensing and quorum quenching hold promise to determine the performance of biological wastewater treatments: An overview

Attenuation effects of iron on dissemination of antibiotic resistance genes in anaerobic bioreactor: Evolution of quorum sensing, quorum quenching and dynamics of community composition

Role of bacterial quorum sensing and quenching mechanism in the efficient operation of microbial electrochemical technologies: A state-of-the-art review

Role of quorum sensing and quorum quenching in anaerobic digestion: A scoping review

Quorum sensing (QS) is a mechanism that enables microbial communication. It is based on the constant secretion of signaling molecules to the environment. The main role of QS is the regulation of vital processes in the cell such as virulence factor production or biofilm formation. Due to still growing bacterial resistance to antibiotics that have been overused, it is necessary to search for alternative antimicrobial therapies. One of them is quorum quenching (QQ) that disrupts microbial communication. QQ-driving molecules can decrease or even completely inhibit the production of virulence factors (including biofilm formation). There are few QQ strategies that comprise the use of the structural analogues of QS receptor autoinductors (AI). They may be found in nature or be designed and synthesized via chemical engineering. Many of the characterized QQ molecules are enzymes with the ability to degrade signaling molecules. They can also impede cellular signaling cascades. There are different techniques used for testing QS/QQ, including chromatography-mass spectroscopy, bioluminescence, chemiluminescence, fluorescence, electrochemistry, and colorimetry. They all enable qualitative and quantitative measurements of QS/QQ molecules. This article gathers the information about the mechanisms of QS and QQ, and their effect on microbial biofilm formation. Basic methods used to study QS/QQ, as well as the medical and biotechnological applications of QQ, are also described. Basis research methods are also described as well as medical and biotechnological application.

Microcystis-dominated cyanobacterial blooms (MCBs) frequently occur in freshwaters worldwide due to massive Microcystis colony formation and severely threaten human and ecosystem health. Quorum sensing (QS) is a direct cause of Microcystis colony formation that drives MCBs outbreak by regulating Microcystis population characteristics and behaviors. Many novel findings regarding the fundamental knowledge of the Microcystis QS phenomenon and the signaling molecules have been documented. However, little effort has been devoted to comprehensively summarizing and discussing the research progress and exploration directions of QS signaling molecules-mediated QS system in Microcystis. This review summarizes the action process of N-acyl homoserine lactones (AHLs) as major signaling molecules in Microcystis and discusses the detailed roles of AHL-mediated QS system in cellular morphology, physiological adaptability, and cell aggregation for colony formation to strengthen ecological adaptability and competitive advantage of Microcystis. The research progress on QS mechanisms in Microcystis are also summarized. Compared to other QS systems, the LuxI/LuxR-type QS system is more likely to be found in Microcystis. Also, we introduce quorum quenching (QQ), a QS-blocking process in Microcystis, to emphasize its potential as QS inhibitors in MCBs control. Finally, in response to the research deficiencies and gaps in Microcystis QS, we propose several future research directions in this field. This review deepens the understanding on Microcystis QS knowledge and provide theoretical guidance in developing strategies to monitor, control, and harness MCBs.

Does Quorum Sensing play a role in microbial shifts along spontaneous fermentation of cocoa beans? An in silico perspective

Quorum sensing (QS) is a regulatory system that regulates the behavior of microbial populations by sensing the concentration of signal molecules that are spontaneously produced and released by bacteria. The strategy of blocking the QS system and inhibiting the production of virulence factors is termed as quorum quenching (QQ). This strategy attenuates virulence without killing the pathogens, thereby weakening the selective pressure on pathogens and postponing the evolution of QQ-mediated drug resistance. In recent years, there have been significant theoretical and practical developments in the field of QS and QQ. In particular, with the development and utilization of marine resources, more and more marine microbial species have been found to be regulated by these two mechanisms, further promoting the research progress of QS and QQ. In this review, we described the diversity of QS signals and QS-related regulatory systems, and then introduced mechanisms related to QS interference, with particular emphasis on the description of natural QQ enzymes and chemicals acting as QS inhibitors. Finally, the exploitation of quorum sensing quenchers and the practical application of QQ were introduced, while some QQ strategies were proposed as promising tools in different fields such as medicine, aquaculture, agriculture and biological pollution prevention areas.