Quorum Sensing in Gram-Negative Bacteria: Small-Molecule Modulation of AHL and AI-2 Quorum Sensing Pathways

Abstract

Contents 1. Introduction 28 1.1. Advantages of the Chemical Biology Approach for the Study of Quorum Sensing Pathways 30 1.2. Important Considerations When Comparing the Results of Different Studies 31 2. AHL-Based Quorum Sensing in Gram-Negative Bacteria 31 2.1.

Frontier studies on highly selective bio-regulators useful for environmentally benign agricultural production

“…This mechanism, known as QS, is needed to develop pathogenicity. 62) When cell density increases and the concentration of AHLs reaches a threshold level, AHLs bind to cognate LuxR-type receptors, and these complexes then activate the expression of target genes. In many pathogenic bacteria, this process results in pathogenic events such as the formation of biofilms and production of virulence factors.…”

“…In many pathogenic bacteria, this process results in pathogenic events such as the formation of biofilms and production of virulence factors. 62) Therefore, QS modulators have potential uses in agrochemical fields by preventing microbial infection in hosts. 63) A compound that specifically regulates QS has been sought in medical and agrochemical pharmacology because it could prevent pathogenicity without killing bacteria, 64) thereby avoiding the emergence of drugresistant strains.…”

Quorum sensing dependent phenotypes and their molecular mechanisms inCampylobacterales

“…ing mechanisms was first described for bioluminescence production of Vibrio (V.) fisheri and V. harveyi. The signalling mechanisms of these autoinducers are highlighted in more detail in other reviews [2,[6][7][8][9][10][11][12][13]. AI-1 signalling has been intensively described in Vibrio spp.…”

“…With increasing cell density the level of AI-1 increases. After reaching a critical threshold of AI-1 molecules within the cells, these molecules can bind and thereby stabilise the intracellular receptor LuxR [6]. The LuxR-type/AI-1 complex functions as transcriptional activator of the luxI-type as well as the target genes.…”

“…The AI-2 signalling are best described for V. harveyi and E. coli: In these systems, the enzyme LuxS cleaves S-ribosylhomocysteine to produce homocysteine and 4,5-dihydroxyl-2,3-pentanedione (DPD), which is the precursor of AI-2 [14]. DPD undergoes spontaneous cyclisation, hydration and boronate ester formation, thereby forming different derivates such as S-THMF-borate (V. harveyi) and R-THMF (E. coli), which are reported to be AI-2 signalling molecules [6]. These molecules are exported to the environment [15] and after reaching a critical threshold, certain signalling cascades are activated (Fig.…”