Quorum sensing, virulence and secondary metabolite production in plant soft-rotting bacteria

Abstract

Quorum sensing describes the ability of bacteria to sense their population density and respond by modulating gene expression. In the plant soft-rotting bacteria, such as Erwinia, an arsenal of plant cell wall-degrading enzymes is produced in a cell density-dependent manner, which causes maceration of plant tissue. However, quorum sensing is central not only to controlling the production of such destructive enzymes, but also to the control of a number of other virulence determinants and secondary metabolites. Erwinia synthesizes both N-acylhomoserine lactone (AHL) and autoinducer-2 types of quorum sensing signal, which both play a role in regulating gene expression in the phytopathogen. We review the models for AHL-based regulation of carbapenem antibiotic production in Erwinia. We also discuss the importance of quorum sensing in the production and secretion of virulence determinants by Erwinia, and its interplay with other regulatory systems.

Future research trends in the major chemical language of bacteria

“…Interestingly, the AHL EsaI/R system of P. stewartii is the paradigm system where the LuxRfamily members act as repressors. More precisely, EsaR represses transcription in the absence of the cognate AHL produced by EsaI (i.e., 3-oxo-C6-HSL) and, at high cell densities upon binding the AHL, the EsaR/3-oxo-C6-HSL complex can no longer bind to DNA, thereby de-repressing target genes (Barnard et al, 2007;Von Bodman et al, 2003). A list of some of the most intensively investigated QS systems are listed in Table I.…”

“…Other important contributions to understanding AHL QS systems include (i) studies on the regulation of antibiotic production and virulence factors in plant pathogenic soft rot Erwinia species (Barnard et al, 2007) and (ii) studies on the regulation of virulence in the plant pathogen Pantoea stewartii, a vascular pathogen which causes wilt and leaf blight in sweet corn and maize. Interestingly, the AHL EsaI/R system of P. stewartii is the paradigm system where the LuxRfamily members act as repressors.…”

“…3-oxo-C6-HSL Carbapenem antibiotics and exoenzymes (Bainton et al, 1992;Barnard et al, 2007;McGowan et al, 1995) …”

Potential Emergence of Multi-quorum Sensing Inhibitor Resistant (MQSIR) Bacteria

“…caratovora 71-AhlI/ExpR along with ExpR2 are controlled through only a single AHL-3OC6HSL. In these Erwinia strains certain AHL molecules are produced in majority, putting the organism to an advantage, in case of any disruption or signal blockade (Table 3) [112,113].…”

Quorum-sensing-regulated transcriptional initiation of plasmid transfer and replication genes in Rhizobium leguminosarum biovar viciae

“…Such 'quorum-sensing' regulation involves the accumulation of the AHLs; as the concentration of AHLs rises, the levels of AHLs within the cells also rise, inducing gene expression by activating regulators that induce expression from specific promoters (Swift et al, 2001). Various cellular processes are regulated in this manner (Barnard et al, 2007;Swift et al, 2001). Many of the regulators that recognize AHLs belong to the LuxR class of DNA-binding proteins, sonamed because LuxR regulates the production of light by bioluminescent bacteria (Fuqua et al, 2001).…”