LuxS-Dependent AI-2 Regulates Versatile Functions in Enterococcus faecalis V583

Abstract

Bacteria utilize a quorum sensing (QS) system to coordinate gene expression by monitoring the concentration of molecules known as autoinducers (AI). In the present study, we confirmed the presence of a LuxS/AI-2 dependent QS system in vancomycin-resistant Enterococcus faecalis V583. Then, the cellular targets controlled by AI-2 were identified by comparative proteomics analysis in order to elucidate the possible role of AI-2 in E. faecalis. Results demonstrated 15 proteins that are differentially expressed upon the addition of AI-2, including proteins involved in metabolism, translation, energy production and/or conversion, and cell wall biogenesis. Glyceraldehyde-3-phosphate dehydrogenase and malate dehydrogenase associated with carbohydrate metabolism and energy production were up-regulated upon inducing by AI-2. In addition, externally added AI-2 could down-regulate acetyl-coenzyme A carboxylase and ornithine carbamoyltransferase, two key enzyme involved in metabolism. All these data suggest that AI-2 signaling may play a role in the regulation of a number of important metabolic properties of E. faecali. We further investigated the role of AI-2 in biofilm formation by E. faecalis, showing the addition of AI-2 to E. faecalis V583 cultures resulted in increased biofilm formation. Our results provide important clues to the role of a LuxS/AI-2 dependent QS system in vancomycin-resistant E. faecalis.

Molecular Mechanism of Quorum-Sensing in Enterococcus faecalis: Its Role in Virulence and Therapeutic Approaches

“…faecalis , like other Gram-positive and Gram-negative bacteria, the LuxS enzyme is involved in the transcriptional regulation of a series of genes, including those involved in ATP generation, translation, cell wall/membrane biogenesis, and nucleotide transport and metabolism [10]. However, the mechanisms that induce the deregulation of genes implicated in these pathways, remain unclear.…”

“…With the advent of proteomic studies in bacteria, it is revealed that the quorum-sensing system not only regulates their specific regulon but also control the expression of many other proteins ranging from surface proteins, transcription factors, virulence, biofilm formation to metabolic pathways [9,10,11]. Proteomics allow a comprehensive understanding of quorum-sensing phenomena and make it possible to better discern patterns of proteins expression in bacteria.…”

“…Shao et al have used the proteomic technique of 2D-PAGE (two-dimensional polyacrylamide gel electrophoresis) and identified 15 differentially expressed quorum-sensing-dependent proteins in vancomycin-resistant E . faecalis [10]. Following its identification, quorum-sensing plays a basic role in biofilm development.…”

“…faecalis regulate much of their pathogenicity and have been documented in several studies [22,23,24,25,26], while the role of the LuxS regulatory mechanism in E . faecalis is less certain [10,27]. …”

Photodynamic inactivation of biofilm: taking a lightly colored approach to stubborn infection

“…Although the elucidation of the molecular circuits affiliated with AI-2 is an ongoing investigation, the role of AI-2 signaling molecules in biofilm formation and maturation has been unequivocally demonstrated in a variety of pathogens. The list includes the nontypeable Haemophilus influenzae [69], Campylobacter jejuni [70], A. actinomycetemcomitans [71], E. faecalis [72], Aeromonas hydrophila [73], V. cholerae [74] and Klebsiella pneumoniae [75]. …”