Abstract
Bacteria use autoinducer molecules to communicate both at intra-species and inter-species levels by quorum sensing. One such cell density-dependent signaling system is the luxS-mediated universal quorum sensing using autoinducer-2 (AI-2). Virulence of several pathogens is determined by an AI-2 system and is related to colonization and infection of the host. From this concept, numerous papers have suggested that AI-2 inhibition is an important strategy toward designing of new antimicrobial agents. However, recent studies indicate that the AI-2 system is also involved in adaptation and survival under environmental stress conditions. Therefore, we hypothesized that interaction between quorum sensing and environmental conditions may be critical in influencing predicted results in a control and when combating of target pathogens. We investigated the growth of enterohemorrhagic Escherichia coli O157:H7 (EHEC) and its luxS-deficient (non AI-2 producing) mutant strain under various stress conditions, and found significant differences in the growth rate under osmotic stress. Moreover, we could also show the impact of the AI-2 molecule on viability in the gastrointestinal tract model representing a complex environmental condition. Differences in vital responses of the strains suggest that AI-2 quorum sensing has a significant influence on the viability of EHEC under environmental stress conditions.
Highlights
Quorum sensing, a secretory bacterial communication system, regulates cell-density dependent behavior with regard to the expression of a specific set of genes determining social behavior (Miller and Bassler, 2001; Winzer and Williams, 2001; Hammer and Bassler, 2003; Leung and Lévesque, 2012; García-Contreras et al, 2014)
In particular, induced significant differences in growth performance. van Kessel et al (2015) reported N-Acyl homoserine lactone (AHL) quorum signaling regulates the response to the osmotic stress in Vibrio harveyi
Numerous studies have reported on quorum sensing of various pathogenic bacteria such as Pseudomonas aeruginosa, (Smith and Iglewski, 2003; O’Loughlin et al, 2013), Listeria monocytogenes (Garmin et al, 2009; Riedel et al, 2009), Salmonella Typhimurium (Surette et al, 1999; Choi et al, 2007), and pathogenic E. coli (Walters and Sperandio, 2006; Medellin-Peña et al, 2007)
Summary
A secretory bacterial communication system, regulates cell-density dependent behavior with regard to the expression of a specific set of genes determining social behavior (Miller and Bassler, 2001; Winzer and Williams, 2001; Hammer and Bassler, 2003; Leung and Lévesque, 2012; García-Contreras et al, 2014). It is assumed that the cell density dependent feature of quorum signal systems, when, associated with signaling absence, do not interfere with bacterial growth or viability; it is expected that quorum signaling inhibition or quenching strategies could avoid resistance of a pathogen (Otto, 2004). Recent fundamental research has unveiled novel roles of the quorum sensing systems to impact collective signaling and global regulation of bacterial physiology (Lee et al, 2013; van Kessel et al, 2015; Thompson et al, 2015). Studies on the involvement of AI-2 quorum sensing in stress-response have provided evidences for a significant impact on bacterial growth, survival, metabolism, adaptation, and colonization (Lebeer et al, 2007, 2008; Moslehi-Jenabian et al, 2009; Christiaen et al, 2014; Sun et al, 2015)
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