Isolation and functional analysis ofluxSinSerratia plymuthicaRVH1

Abstract

Autoinducer-2 (AI-2) is a signalling molecule proposed to act as a 'universal' signal for interspecies communication, regulating niche-specific genes with diverse functions in various bacteria. We have previously reported the production of AI-2 in strains from different Serratia species and recently, the luxS gene of two Serratia strains was isolated and shown to affect distinct phenotypes. In the current work, we have identified the luxS gene of Serratia plymuthica RVH1, and studied its effect on the N-acyl-L-homoserine lactone-regulated 2,3-butanediol fermentation, production of extracellular protease, chitinase, nuclease and antibacterial compound, and on biofilm formation. None of these phenotypes was affected by luxS knockout. However, overexpression of the luxS gene in RVH1, which was accompanied by an increased production of AI-2, resulted in a slower growth. This growth retardation was also observed when RVH1 was grown in spent culture medium from the AI-2-overproducing strain, but not in spent culture medium from the luxS knockout strain. These results suggest that luxS primarily fulfils a metabolic role and may not regulate a coordinated behaviour controlled by cell-to-cell signalling in S. plymuthica RVH1.

Overexpression of luxS Cannot Increase Autoinducer‐2 Production, Only Affect the Growth and Biofilm Formation in Streptococcus suis

“…Our result that the strain with the plasmid-born luxS showed slower growth is in agreement with the observations of Van et al for Serratia plymuthica RVH1 [15] and Zhang et al for Edwardsiella tarda [16]. However, they all reported that overexpression of the luxS gene, which was accompanied by an increased production of AI-2, resulted in a slower growth [15, 16]. In contrast, these groups had not detected the level of pfs transcription in the overexpression strain.…”

The Role of luxS in the Fire Blight Pathogen Erwinia amylovora Is Limited to Metabolism and Does Not Involve Quorum Sensing

“…Thus, the observed growth pattern was not caused by an extracellular signal, but was likely of a metabolic, intracellular nature. This conclusion is strengthened by analogous results recently obtained using a similar approach in other luxS-positive bacteria, such as Staphylococcus aureus or Serratia plymuthica (Doherty et al 2006;Van Houdt et al 2006). An additional indication that, in Erwinia amylovora, luxS is involved in sulfur and amino acid metabolism is the position of the luxS open reading frame in the E. amylovora genome.…”

Quorum sensing inSerratia

“…For S. plymuthica RVH1 knock‐out of luxS had no detectable effect on the AHL‐regulated phenotypes, nor on biofilm formation. However, overproduction of AI‐2 in RVH1 strains carrying luxS on a multicopy plasmid caused attenuated growth (Van Houdt et al ., 2006b). As the signal transduction pathway has not been identified, these results do not support a role in cell–cell communication for LuxS and AI‐2 in S. plymuthica RVH1, but rather suggest that the phenotypes associated with luxS knockout reported earlier in other Serratia spp.…”