Chromobacterium Violaceum: A Model for Evaluating the Anti-Quorum Sensing Activities of Plant Substances

Abstract

In the new antibiotic era, the exponential increase in multiresistant bacterial strains has become the main global health problem. Many researchers have focused their efforts on exploring novel or combined strategies for combating bacterial resistance. Good knowledge of the molecular mechanisms of resistance and bacterial virulence factors as key targets provides us with a good basis for resolving the problem. One particularly attractive and promising strategy is to attack the main regulatory “network” of bacterial virulence determinants known as quorum sensing (QS). The inhibition of QS signals will be a novel means of screening more effective quorum-sensing inhibitors (QSIs) and will play a key role in the use of next-generation antimicrobials in the battle against resistance. This motivated the present review to provide a comprehensive clarification of the regulatory mechanisms of quorum-sensing signaling pathways in Chromobacterium violaceum and the discovery of potential plant quorum-sensing inhibitors.

An Overview of Biofilm-Associated Infections and the Role of Phytochemicals and Nanomaterials in Their Control and Prevention

“…When the goal is prevention, efforts should be directed towards creating conditions that hinder or prevent biofilm formation in its initial stages. This includes actions such as blocking and preventing the adhesion of bacteria to the substrate [ 65 ]; blocking the synthesis stages of the biofilm matrix; inhibiting the quorum-sensing signaling cascade; and disrupting of communication between bacteria [ 66 , 67 ]. Treatment as a strategy aims to prevent the biofilm from growing and occupying new niches, which can lead to infections.…”

Evaluation of novel compounds as anti-bacterial or anti-virulence agents

“…The simplest approach for screening QSIs is the biological assay based on natural strain Chromobacterium violaceum , Gram-negative bacterium that can produce purple pigment violacein and therefore form purple colonies on common laboratory media ( Lu et al., 2022 ). The violacein pigment is encoded by the vio operon and the expression of this pigment is QS-regulated, which is why these bacteria are often used as a model system for screening of QSIs in the laboratory ( Kothari et al., 2017 ; Dimitrova et al., 2023 ). The loss of the pigment, in turn, indicates inhibition of QS, and those compounds that induce inhibition of the violacein production, without affecting bacterial growth, can be considered as true QSIs.…”

Anti-Biofilm and Anti-Quorum-Sensing Activity of Inula Extracts: A Strategy for Modulating Chromobacterium violaceum Virulence Factors

“…In pathogenic bacteria, the coordinated "behaviour and actions" are essential for a successful infection, which is achieved by the QS communication between them [25]. However, impaired quorumsensing communication leads to decreased bacterial pathogenicity and the blockade of infection progression [5,6,23,26,27]. Anti-quorum-sensing agents aim not to kill bacteria, but rather to reduce their bacterial virulence [28].…”

“…As a result, bacteria collectively regulate their energy-intensive processes so that they are activated only when needed and with maximum efficiency. Other key mechanisms, such as virulence, gene expression, pathogenicity, and antibiotic resistance, are thus regulated [5,6]. The ability to interfere with QS signals and disrupt essential components, such as extracellular DNA (eDNA), proteins, and lipopolysaccharides, suppresses the formation of the polymer matrix [7] and virulence factors, inhibits cell adhesion and attachment, and ultimately leads to the blocking of the "QS-network" and biofilm inhibition [8].…”

“…Chromobacterium violaceum is a motile, free-living, saprophytic Gram-negative, facultative, deep-purple colony-forming anaerobic bacterium [6,9]. The color of its colonies is due to the release of the pigment violacein, encoded by the vio operon, whose expression is controlled by QS signals.…”