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The LuxI/LuxR–type quorum sensing in Gram-negative bacteria. The LuxI-like protein is an autoinducer synthase that catalyzes the formation of a specific acyl-homoserine lactone (AHL). The AHL freely diffuses through the cell membrane at high cell density. The LuxR is a transcriptional regulator that binds to the diffusing AHL and in turn activates the transcription of its target genes.
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Many bacteria are known to regulate their cooperative activities and physiological processes through a mechanism called quorum sensing (QS), in which bacterial cells communicate with each other by releasing, sensing and responding to small diffusible signal molecules. The ability of bacteria to communicate and behave as a group for social interacti...
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Introduction: The infections by S. aureus threaten to turn into a serious problem of public health. The capacity of the bacteria as colonizing and infected agent in humans is due to the wide spectrum of factors that it possesses, so much of colonization as of virulence. Between them, the phenol-soluble modulins (PSMs) have reached a height because...
Pseudomonas aeruginosa is identified as a versatile opportunistic microorganism with metabolic diversity contributing to a wide range of health burdens, especially in immunocompromised patients. This bacterium is the cause of 10 to 20% of nosocomial infections. In this study, we evaluated the phenotypic characterizations of biofilm formation in P....
Background: Quorum sensing (QS) is considered an important behavior of bacterial cells that communicate with each other. Pyocyanin produced by Pseudomonas aeruginosa is one QS activity. Its synthesis can affect in the presence of essential oils.
Unlabelled:
Vibrio cholerae, the Gram-negative bacterium abruptly colonizes the human intestine causing diarrhea, employing quorum sensing (QS) system as the major survival technique for mediating biofilm formation, virulence, competence, etc. Two distinct QS systems coordinated by the auto-inducer molecules, cholera-specific CqsA/S system and uni...
Citations
... This shows that DNA is an integral component of these structures. The supernatant from M. avium biofilm cultures, induced biofilm formation in planktonic cells, suggesting quorum sensing could assist in biofilm formation [80]. ...
Mycobacterium avium ssp. paratuberculosis (MAP) has been implicated in the development of Crohn’s disease (CD) for over a century. Similarities have been noted between the (histo)pathological presentation of MAP in ruminants, termed Johne’s disease (JD), and appearances in humans with CD. Analyses of disease presentation and pathology suggest a multi-step process occurs that consists of MAP infection, dysbiosis of the gut microbiome, and dietary influences. Each step has a role in the disease development and requires a better understanding to implementing combination therapies, such as antibiotics, vaccination, faecal microbiota transplants (FMT) and dietary plans. To optimise responses, each must be tailored directly to the activity of MAP, otherwise therapies are open to interpretation without microbiological evidence that the organism is present and has been influenced. Microscopy and histopathology enables studies of the mycobacterium in situ and how the associated disease processes manifest in the patient e.g., granulomas, fissuring, etc. The challenge for researchers has been to prove the relationship between MAP and CD with available laboratory tests and methodologies, such as polymerase chain reaction (PCR), MAP-associated DNA sequences and bacteriological culture investigations. These have, so far, been inconclusive in revealing the relationship of MAP in patients with CD. Improved and accurate methods of detection will add to evidence for an infectious aetiology of CD. Specifically, if the bacterial pathogen can be isolated, identified and cultivated, then causal relationships to disease can be confirmed, especially if it is present in human gut tissue. This review discusses how MAP may cause the inflammation seen in CD by relating its known pathogenesis in cattle, and from examples of other mycobacterial infections in humans, and how this would impact upon the difficulties with diagnostic tests for the organism.
... This matrix protects microbial cells from adverse environmental conditions. Biofilm-forming microbes include bacteria, fungi, algae, and other microorganisms that work together through quorum sensing processes, functioning as a cohesive [121,122]. Recent reports have highlighted the beneficial impact of biofilms on crop productivity. Compared to single microorganism-based biofertilizers, biofilm biofertilizers have shown significant advantages [123,124]. ...
The continuous growth of the world’s population and the escalating demand for food raise serious concerns about the future of agriculture. According to FAO’s estimates, agricultural product demand is expected to rise by 60% by 2030. However, the increasing use of chemical fertilizers has shown adverse effects on the environment and living organisms. In this context, biofertilizers offer a promising alternative to hazardous chemicals, supporting agricultural sustainability. Biofertilizers are known for their eco-friendly, non-toxic, and cost-effective nature, contributing to soil health, structure, and biodiversity preservation. Nevertheless, they face challenges, including poor shelf-life, on-field stability, sensitivity to fluctuating environmental conditions (such as temperature, radiation, and pH), limitations in long-term use, scarcity of beneficial bacterial strains, susceptibility to desiccation, and high required doses for large coverage areas. Commercially available microbe-based biofertilizers have not always met expectations in field conditions due to various reasons. While there have been advancements in biofertilizers to improve efficiency and popularity among farmers, the need to explore next-generation biofertilizers remains essential. This review primarily focuses on advanced and next-generation biofertilizers, such as PGPB (Plant Growth-Promoting Bacteria), fungal biofertilizers, nanobiofertilizers, and biofilm biofertilizers, aiming to address these challenges and propel sustainable agriculture forward.
Graphical Abstract
... Bacteria can utilize QS to perceive changes in population density and adapt their activity accordingly. This ability enables them to flourish and enhance their pathogenicity in various environmental conditions (Chen et al., 2011;Li and Tian, 2012). Directing efforts towards QS pathways provides a potential strategy for the treatment of bacterial infections and reduces their associated pathogenicity (Hentzer et al., 2003;Kipnis et al., 2006). ...
... 14 response to alterations in cell density. QS relies on signaling molecules named autoinducers (AIs), which are released by bacteria into their surroundings (Schneider et al., 2002;Rasmussen and Givskov, 2006;Bottomley et al., 2007;Van Houdt et al., 2007;Li and Tian, 2012;Srivastava et al., 2014;Wysoczynski-Horita et al., 2018). In the receptor-inducer model Sulforaphane, at a concentration below the minimum inhibitory concentration (sub-MIC), reduced the expression of the following quorum sensing (QS)-encoding genes in PAO1: (A) rhlI, (B) rhlR, (C) lasI, (D) lasR, (E) pqsA, and (F) pqsR. ...
Background
P. aeruginosa, a significant bacterium, can cause severe illness and resistance to antibiotics. Quorum sensing (QS) systems regulate virulence factors production. Targeting QS could reduce bacteria pathogenicity and prevent antibiotic resistance. Cruciferous vegetables contain sulforaphane, known for its anti-inflammatory, antioxidant, anticancer, and antimicrobial properties.
Aim
We aimed to examine the inhibitory influences of sulforaphane, at a sub-inhibitory concentration (¼ minimum inhibitory concentration, MIC), on virulence and QS in P. aeruginosa.
Materials and methods
The sulforaphane’s anti-virulence actions at sub-inhibitory concentrations were explored in vitro and in vivo. A sub-MIC concentration of sulforaphane was combined with anti-pseudomonal drugs, and the results of this combination were assessed. The virtual affinity of sulforaphane for the receptors of QS was studied, and its effect on the expression of QS genes was quantified.
Results
Sulforaphane significantly decreased the biofilm formation, motility, ability to withstand oxidative stress, and the synthesis of virulence extracellular enzymes such as proteases, hemolysins, and elastase, as well as other virulence factors like pyocyanin. In addition, sulforaphane lessened the severity of P. aeruginosa infection in mice. Sulforaphane reduced the antipseudomonal antibiotics’ MICs when used together, resulting in synergistic effects. The observed anti-virulence impacts were attributed to the ability of sulforaphane to inhibit QS via suppressing the QS genes’ expression.
Conclusion
Sulforaphane shows promise as a potent anti-virulence and anti-QS agent that can be used alongside conventional antimicrobials to manage severe infections effectively. Furthermore, this study paves the way for further investigation of sulforaphane and similar structures as pharmacophores for anti-QS candidates.
... Numerous clinical trials have confirmed a negative correlation between P. gingivalis and S. mutans both in subgingival plaque and saliva before and after systemic treatment of periodontal disease patients [39]. Different degrees of antagonism were found between the two bacteria when they were co-cultured, in which P. gingivalis was found to interfere with the quorum sensing (QS) system of S. mutans, thereby diminishing its biofilm-forming ability, acid tolerance, and bacteriocin-producing ability [54]. However, some studies [37] have also shown a positive correlation between other periodontal pathogens such as F. nucleatum, Actinobacillus and S. mutans, which may be mediated by the co-aggregation of F. nucleatum [55] and the high genetic variability of Actinobacillus strain [56]. ...
Objectives
Recent evidence suggested a link between periodontitis (PD) and dental caries, but the trends and nature of this association remained unclear. The overall aim of this study was to critically assess the correlation of two disorders.
Methods
A comprehensive search was conducted within the PUBMED and EMBASE databases including grey literatures up to July 5th, 2023. The Newcastle–Ottawa scale was used to qualitatively evaluate the risk of bias.
Results
Overall, 18 studies were included. In terms of caries risk in PD patients, the prevalence of caries was increased by PD (OR = 1.57, 95%CI:1.20–2.07), both in crown (OR = 1.03, 95%CI:1.01–1.05) and root caries (OR = 2.10, 95%CI:1.03–4.29). Odds of caries were also raised by PD severity (OR moderate = 1.38, 95%CI:1.15–1.66; OR severe = 2.14, 95%CI:1.74–2.64). Besides, patients with PD exhibited a higher mean number of decayed, missing and filled teeth (DMFT) and decayed and filled root teeth (DFR) [weighted mean difference (WMD)DMFT = 0.87, 95%CI: -0.03–1.76; WMDDFR = 1.13, 95%CI: 0.48–1.78]. Likewise, patients with caries had an elevated risk of PD (OR = 1.79, 95%CI:1.36–2.35). However, Streptococcus mutans, one of the main pathogens of caries, was negatively correlated with several main pathogens of periodontitis.
Conclusions
This study indicated a positive correlation between dental caries and periodontitis clinically, while the two disease-associated pathogens were antagonistic.
Clinical relevance
Further research, including clinical cohort studies and mechanisms of pathogens interaction is needed on this link for better prevention and treatment of PD and caries. In addition, innovative prevention strategies need to be developed and incorporated in dental practices to prevent these two highly prevalent oral diseases.
... The role of QS in the formation of bacterial biofilms represents a crucial aspect of microbial behavior (Li and Tian, 2012). As Thymoquinone significantly downregulated the expression of QS genes (A) rhlI, (B) rhlR. ...
Pseudomonas aeruginosa belongs to the critical pathogens that represent a global public health problem due to their high rate of resistance as listed by WHO. P. aeruginosa can result in many nosocomial infections especially in individuals with compromised immune systems. Attenuating virulence factors by interference with quorum sensing (QS) systems is a promising approach to treat P. aeruginosa-resistant infections. Thymoquinone is a natural compound isolated from Nigella sativa (black seed) essential oil. In this study, the minimum inhibitory concentration of thymoquinone was detected followed by investigating the antibiofilm and antivirulence activities of the subinhibitory concentration of thymoquinone against P. aeruginosa PAO1. The effect of thymoquinone on the expression of QS genes was assessed by quantitative real-time PCR, and the protective effect of thymoquinone against the pathogenesis of PAO1 in mice was detected by the mouse survival test. Thymoquinone significantly inhibited biofilm, pyocyanin, protease activity, and swarming motility. At the molecular level, thymoquinone markedly downregulated QS genes lasI, lasR, rhlI, and rhlR. Moreover, thymoquinone could protect mice from the pathologic effects of P. aeruginosa increasing mouse survival from 20% to 100%. In conclusion, thymoquinone is a promising natural agent that can be used as an adjunct therapeutic agent with antibiotics to attenuate the pathogenicity of P. aeruginosa.
... On the other hand, quorum quenching (QQ) is a process that results in the intrusion of bacterial cross talk (QS) [130]. QS is responsible for various processes in bacteria such as virulence factors production, biofilm formation, sporulation, bioluminescence and bacteria-host interactions [131,132]. Metallic nanoparticles can act as potent anti QS inhibitors by affecting the mechanism of cell-cell communication. The strategies involving quorum quenching include the inhibition of signal molecules synthesis, inactivation or degradation of signalling molecules and interruption of signal molecule-receptor formation thus stopping the signal transduction cascade [133,134]. ...
The emergence of antimicrobial resistance among biofilm forming pathogens aimed to search for the efficient and novel alternative strategies. Metallic nanoparticles have drawn a considerable attention because of their significant applications in various fields. Numerous methods are developed for the generation of these nanoparticles however, mycogenic (fungal-mediated) synthesis is attractive due to high yields, easier handling, eco-friendly and being energy efficient when compared with conventional physico-chemical methods. Moreover, mycogenic synthesis provides fungal derived biomolecules that coat the nanoparticles thus improving their stability. The process of mycogenic synthesis can be extracellular or intracellular depending on the fungal genera used and various factors such as temperature, pH, biomass concentration and cultivation time may influence the synthesis process. This review focuses on the synthesis of metallic nanoparticles by using fungal mycelium, mechanism of synthesis, factors affecting the mycosynthesis and also describes their potential applications as antioxidants and antibiofilm agents. Moreover, the utilization of mycogenic nanoparticles as quorum quenching agent in hampering the bacterial cell-cell communication (quorum sensing) has also been discussed.
... It is currently understood that the microorganisms, referred to as the microbiota, comprising the human microbiome exist not as coexisting individual unicellular organisms, but rather as intricately organized communities adhering to surfaces in the form of biofilms [1]. These biofilms exhibit a high level of regulation, both structurally and functionally, and are characterized by interactions among different species, including collaborations and antagonisms, which collectively contribute to the stability of the ecological system [32]. ...
This comprehensive review delves into the forefront of research on the human oral microbiome, exploring recent advancements that span microbial colonization, state-of-the-art detection methodologies, and the complex interplay involved in disease progression. Through an exhaustive analysis of the contemporary literature, we illuminate the dynamic orchestration of microbial communities within the oral cavity, underscoring their pivotal role in health and disease. Cutting-edge detection techniques, including metagenomics and high-throughput sequencing, are discussed regarding their transformative impact on understanding the intricacies of oral microbial ecosystems. As we stand on the cusp of a new decade, this review anticipates a paradigm shift in the field, emphasizing the potential for rapid identification and targeted management of detrimental oral microorganisms. Insights gained from this exploration not only contribute to our fundamental understanding of the oral microbiome but also hold promise for the development of innovative therapeutic strategies to maintain oral health. This article aims to serve as a valuable resource for researchers, clinicians, and public health professionals engaged in unraveling the mysteries of the microbial symphony within the human oral cavity.
... Gram-positive and -negative bacteria employ diverse communities to control the virulence factors production during the different stages of infection, however, the quorum sensing (QS) systems play the principal roles in controlling bacterial virulence (Juhas et al., 2005;Li and Tian, 2012;Jiang and Li, 2013;Elfaky et al., 2022;Zeng et al., 2022). For instance, biofilm formation and production of diverse virulence factors are orchestrated in the population mainly by QS systems in both Grampositive and -negative bacteria (Parsek et al., 1999;Rutherford and Bassler, 2012;Papenfort and Bassler, 2016;Hegazy and Abbas, 2017). ...
The rise of antibiotic resistance in bacteria is becoming a global concern, particularly due to the dwindling supply of new antibiotics. This situation mandates the discovery of new antimicrobial candidates. Plant-derived natural compounds have historically played a crucial role in the development of antibiotics, serving as a rich source of substances possessing antimicrobial properties. Numerous studies have supported the reputation of 6-gingerol, a prominent compound found in the ginger family, for its antibacterial properties. In this study, the antibacterial activities of 6-gingerol were evaluated against Gram-negative bacteria, Acinetobacter baumannii and Klebsiella pneumoniae, with a particular focus on the clinically significant Gram-negative Pseudomonas aeruginosa and Gram-positive bacteria Staphylococcus aureus. Furthermore, the anti-virulence activities were assessed in vitro, in vivo, and in silico. The current findings showed that 6-gingerol’s antibacterial activity is due to its significant effect on the disruption of the bacterial cell membrane and efflux pumps, as it significantly decreased the efflux and disrupted the cell membrane of S. aureus and P. aeruginosa. Furthermore, 6-gingerol significantly decreased the biofilm formation and production of virulence factors in S. aureus and P. aeruginosa in concentrations below MICs. The anti-virulence properties of 6-gingerol could be attributed to its capacity to disrupt bacterial virulence-regulating systems; quorum sensing (QS). 6-Gingerol was found to interact with QS receptors and downregulate the genes responsible for QS. In addition, molecular docking, and molecular dynamics (MD) simulation results indicated that 6-gingerol showed a comparable binding affinity to the co-crystalized ligands of different P. aeruginosa QS targets as well as stable interactions during 100 ns MD simulations. These findings suggest that 6-gingerol holds promise as an anti-virulence agent that can be combined with antibiotics for the treatment of severe infections.
... This finding suggests that synergistic interactions among microorganisms occurred more frequently in the presence of BPA. Quorum sensing, a communication mechanism in bacteria involving autoinducer molecules, plays a crucial role in microbial coordination, adaptation, and response to environmental changes (Li and Tian 2012). For example: ...
... (1) quorum sensing allows microorganisms to synchronize the production of extracellular polymeric substances (EPS), which facilitate biofilm formation (Li and Tian 2012). Biofilms provide a protective environment for microorganisms, enhancing their resilience to environmental stresses (Yin et al. 2019). ...
The widespread use of bisphenol A (BPA) has resulted in the emergence of new pollutants in various environments, particularly concentrated in sewage sludge. This study investigated the effects of BPA on sludge anaerobic digestion, focusing specifically on the interaction of microbial communities and their metabolic responses. While the influence of BPA on methane accumulation is not significant, BPA still enhanced the conversion of soluble COD, protein, and polysaccharides. BPA also positively influenced the hydrolysis-acidogenesis process, leading to 17% higher concentrations of volatile fatty acids (VFAs). Lower BPA levels (0.2–0.5 mg/kg dw) led to decreased hydrolysis and acidogenesis gene abundance, indicating metabolic inhibition; conversely, higher concentrations (1–5 mg/kg dw) increased gene abundance, signifying metabolic enhancement. Diverse methane metabolism was observed and exhibited alterations under BPA exposure. The presence of BPA impacted both the diversity and composition of microbial populations. Bacteroidetes, Proteobacteria, Firmicutes, and Chloroflexi dominated in BPA-treated groups and varied in abundance among different treatments. Changes of specific genera Sedimentibacter, Fervikobacterium, Blvii28, and Coprothermobacter in response to BPA, affecting hydrolysis and acetogenesis. Archaeal diversity declined while the hydrogenotrophic methanogen Methanospirillum thrived under BPA exposure. BPA exposure enabled microorganisms to form structured community interaction networks and boost their metabolic activities during anaerobic digestion. The study also observed the enrichment of BPA biodegradation pathways at high BPA concentrations, which could interact and overlap to ensure efficient BPA degradation. The study provides insights into the digestion performance and interactions of microbial communities to BPA stress and sheds light on the potential effect of BPA during anaerobic digestion.
... However, the survival of these keystone species is also affected by the growth stage of the host, with the persistence of core members contingent on core functions that are adapted for success in the leaf environment (Bell et al. 2021;Müller et al. 2016b). Another type of interaction in the phyllosphere is facilitation: examples include the promotion of fitness of bacterial foliar pathogens through intra-species communication (Li et al. 2019a) and the increased survival of bacterial species through inter-species signaling (He et al. 2022;Li and Tian 2012). ...
The phyllosphere, or plant leaf surface, represents a microbial ecosystem of considerable size, holding extraordinary biodiversity and enormous potential for the discovery of new products, tools, and applications in biotechnology, agriculture, medicine, and elsewhere. This mini-review highlights the applied microbiology of the phyllosphere as an original field of study concerning itself with the genes, gene products, natural compounds, and traits that underlie phyllosphere-specific adaptations and services that have commercial and economic value for current or future innovation. Examples include plant-growth-promoting and disease-suppressive phyllobacteria, probiotics and fermented foods that support human health, as well as microbials that remedy foliar contamination with airborne pollutants, residual pesticides, or plastics. Phyllosphere microbes promote plant biomass conversion into compost, renewable energy, animal feed, or fiber. They produce foodstuffs such as thickening agents and sugar substitutes, industrial-grade biosurfactants, novel antibiotics and cancer drugs, as well as enzymes used as food additives or freezing agents. Furthermore, new developments in DNA sequence-based profiling of leaf-associated microbial communities allow for surveillance approaches in the context of food safety and security, for example, to detect enteric human pathogens on leafy greens, predict plant disease outbreaks, and intercept plant pathogens and pests on internationally traded goods.
Key points
• Applied phyllosphere microbiology concerns leaf-specific adaptations for economic value
• Phyllobioprospecting searches the phyllosphere microbiome for product development
• Phyllobiomonitoring tracks phyllosphere microbial profiles for early risk detection
Graphical Abstract
