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Botanicals and the Gut Microbiome
Published in Namrita Lall, Medicinal Plants for Cosmetics, Health and Diseases, 2022
Quorum sensing is the communication pathway between bacterial species that is based on chemical signals and through which their behavior can be determined. The main signaling molecule is primarily N-acyl homoserine lactones. Quorum sensing controls a number of features within a bacterial colony, such as their resistance, their motility and how they form biofilms, as well as their level of pathogenicity (McCarthy and O’Gara, 2015). Next-generation antimicrobials have the ability to decrease resistance and target the communication between bacteria known as quorum sensing/signaling. Ingested antibiotic adjuvants can increase the oral bioavailability of the antibiotic by inhibiting the quorum sensing between the pathogenic bacteria and making them less virulent and pathogenic, rendering them more susceptible to antibiotics. The gut microbiota mainly disrupts the communication between the pathogenic bacterial colonies and therefore prevents from taking place the initial stages of infection which involve integration within the host (Clemente et al., 2012).
Proteus
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
María José González, Pablo Zunino, Paola Scavone
Quorum sensing is the communication between bacterial cells in response to fluctuations in cell-population density and other inducers. The coordinate population response is controlled by diffusible molecules produced by individuals named autoinducers. N-acyl homoserine lactone (AHL) signaling molecules are utilized by several gram-negative species to sense population density and coordinate gene expression [62]. Despite P. mirabilis lacking a clear AHL synthase (LuxI) homologue, it encodes a LuxR family transcriptional regulator that seems to produce compounds with AHL-like activity [63,64]. The quorum-sensing molecule autoinducer 2 (AI-2), encoded by luxS, can mediate intra- and interspecies interactions. P. mirabilis possesses a luxS homologue and produces AI-2. However, Schneider et al. found that the mutation of luxS in P. mirabilis strain BB2000 does not significantly affect swarming, virulence factors production, or survival in a mouse model. This suggests that AI-2 does not contribute to pathogenicity, but it might influence gene expression in other species that use this signaling molecule [65]. Putrescine has also been proposed as an extracellular signal that is capable of mediating cell-to-cell communication [66]. Putrescine is a component of the outer membrane for some P. mirabilis strains [67]. If P. mirabilis utilizes putrescine for signaling, the bacteria may respond to putrescine produced by other species or scavenged from the host. P. mirabilis upregulates a putrescine transporter during experimental infection, but the signaling capabilities of this molecule remain unclear [68].
Proteus
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Paola Scavone, Victoria Iribarnegaray, Pablo Zunino
Quorum sensing describes the communication between bacterial cells, whereby a coordinated population response is controlled by diffusible molecules produced by individuals, often known as autoinducers. The influence of quorum-sensing molecules in Proteus strains is much less known compared to Pseudomonas or Escherichia. N-acyl homoserine lactone (AHL) signaling molecules are utilized by several Gram-negative species to sense population density and coordinate gene expression [32]. P. mirabilis lacks a clear AHL synthase (LuxI) homologue and does not seem to produce this type of signaling molecule [12,33]. However, P. mirabilis encodes a LuxR family transcriptional regulator and seems to produce compounds with AHL-like activity. Previous studies found that the addition of exogenous AHL to a P. mirabilis population had a strain-specific impact on virulence factor expression, swarming, and biofilm formation [34,35]. The quorum-sensing molecule autoinducer 2 (AI-2), encoded by luxS, can mediate both intra- and interspecies interactions. P. mirabilis possesses a luxS homologue and produces AI-2 [36]. However, mutation of luxS in P. mirabilis str. BB2000 does not significantly affect swarming, virulence factor production, or survival in a mouse model, suggesting that AI-2 does not contribute to pathogenicity [36]. This lack of phenotype might indicate that P. mirabilis uses LuxS strictly as part of the activated methyl cycle, particularly as P. mirabilis str. HI4320 contains no clear homologue of the Lsr system for sensing and responding to AI-2. However, AI-2 produced by P. mirabilis might influence gene expression in other species that use this signaling molecule. Other studies have reported that the presence of a quorum-sensing molecule (N-butanoyl homoserine lactone, BHL) increased P. mirabilis biofilm thickness and ureolytic activity. Laser interferometric determination of diffusion showed that urea easily diffuses through P. mirabilis biofilm, while acetohydroxamic acid (AHA) is blocked. This may suggest that the use of urease inhibitors in catheter-associated UTIs (CAUTIs) may be less effective than in other urease-associated infections [37].
Presence of potent inhibitors of bacterial biofilm associated proteins is the key to Citrus limon’s antibiofilm activity against pathogenic Escherichia coli
Published in Biofouling, 2023
Songeeta Singha, Rajendran Thomas, Abinash Kumar, Devarshi Bharadwaj, Jai N. Vishwakarma, Vivek Kumar Gupta
Biofilm formation involves accumulation of signaling molecules called auto-inducers or bacterial pheromones that eventually mediate inter-cellular communication, known as quorum sensing (QS). It has been reported that E. coli do not synthesize N-acyl homoserine lactones (AHLs) due to the absence of LuxI homolougues, however, they encode a transcription factor of LuxR family, named SdiA which responds to the AHLs produced by other bacterial species (Almeida et al. 2016). These molecules are reported to regulate adhesion to host epithelial cells, biofilm formation on polystyrene surfaces and induce resistance to acidic pH (Hobley et al. 2015). Similarly, the E. coli biofilm matrix includes the proteins RbmA and RbmC, whose transcription is co-regulated with the vps genes which in turn are required for the reinforcement of the biofilm structure as well as the recruitment of new cells (Smith et al. 2015).
Impact of quorum sensing signaling molecules in gram-negative bacteria on host cells: current understanding and future perspectives
Published in Gut Microbes, 2022
Yingping Xiao, Huicong Zou, Jingjing Li, Tongxing Song, Wentao Lv, Wen Wang, Zhenyu Wang, Shiyu Tao
Bacterial QS, also known as self-induction, is a mechanism by which bacteria exchange intracellular or intercellular information, coordinate population behavior, and regulate gene expression, all of which depend on population density.8 When a bacterial community reaches a certain density, it turns on the expression of genes related to bacterial community density by secreting diffusible signaling small molecules (also known as QSSMs). QSSMs diffuse into the environment, and when the signaling molecules in the environment reach a certain threshold concentration, they induce the expression of specific genes in bacteria that are dependent on cell density, thus causing bacteria to exhibit new behavioral characteristics on a community scale such as biological luminescence, regulation of virulence factor secretion, budding spore formation or biofilm formation, cell differentiation, motility, and extracellular polysaccharide formation.9,10 A variety of microbial-related QSSMs have been identified. For gram-negative bacteria, most QSSMs belong to the N-acyl-homoserine lactone (AHL) family. The main differences among different AHLs are the length of the N-side chain, the substituents at the 3-carbon position, and the presence or absence of one or more unsaturated bonds in the side chain.11,12
Ecofriendly phytosynthesized zirconium oxide nanoparticles as antibiofilm and quorum quenching agents against Acinetobacter baumannii
Published in Drug Development and Industrial Pharmacy, 2022
Muhammad Hussnain Siddique, Sumreen Hayat, Saima Muzammil, Asma Ashraf, Arif Muhammad Khan, Muhammad Umar Ijaz, Mohsin Khurshid, Muhammad Afzal
Acinetobacter baumannii has emerged as one of the most exacerbating hospital-acquired pathogens [14] An increase in the prevalence of multidrug-resistant strains has limited the therapeutic options to manage the infections caused by A. baumannii, that is also included among the ESKAPE pathogen [14]. One of the major factors contributing toward the survival of A. baumannii in unfavorable conditions, such as hospital settings is the formation of biofilms and extracellular polymeric substance (EPS) production [15]. Important virulence attributes, such as biofilm formation and motility have been controlled by N-acyl-homoserine lactone (AHL)-mediated quorum sensing (QS) system in various species of the A. calcoaceticus-A. baumannii complex [16]. Quorum quenching (QQ) is a process resulting in the interruption of QS. Molecular actors of QQ are distinct in their mode of action (Cleavage of QS-signals, competitive inhibition), nature (chemicals, enzymes), and targets as all of the major steps of QS can be disturbed by QQ [17].