SdiA, an N-Acylhomoserine Lactone Receptor, Becomes Active during the Transit of Salmonella enterica through the Gastrointestinal Tract of Turtles

Department of Microbiology, The Ohio State University, Columbus, Ohio, United States of America.
PLoS ONE (Impact Factor: 3.23). 02/2008; 3(7):e2826. DOI: 10.1371/journal.pone.0002826
Source: PubMed


LuxR-type transcription factors are typically used by bacteria to determine the population density of their own species by detecting N-acylhomoserine lactones (AHLs). However, while Escherichia and Salmonella encode a LuxR-type AHL receptor, SdiA, they cannot synthesize AHLs. In vitro, it is known that SdiA can detect AHLs produced by other bacterial species.
In this report, we tested the hypothesis that SdiA detects the AHL-production of other bacterial species within the animal host. SdiA did not detect AHLs during the transit of Salmonella through the gastrointestinal tract of a guinea pig, a rabbit, a cow, 5 mice, 6 pigs, or 12 chickens. However, SdiA was activated during the transit of Salmonella through turtles. All turtles examined were colonized by the AHL-producing species Aeromonas hydrophila.
We conclude that the normal gastrointestinal microbiota of most animal species do not produce AHLs of the correct type, in an appropriate location, or in sufficient quantities to activate SdiA. However, the results obtained with turtles represent the first demonstration of SdiA activity in animals.

Download full-text


Available from: Sara D Lawhon
  • Source
    • "Dyszel et al. (2010) have reported that Rck confers a selective advantage for intestinal colonization in mice when it is expressed. Moreover, as rck is regulated by an unidentified system, which is independent of SdiA at 37 and 42 • C (Smith et al., 2008), it is conceivable that Rck has a role which is not only restricted to the gastrointestinal tract and which could be induced in only some animal species. The role of quorum sensing in Salmonella pathogenesis in animals and its impact on Rck expression is still poorly characterized . "
    [Show abstract] [Hide abstract]
    ABSTRACT: Salmonella enterica species are Gram-negative bacteria, which are responsible for a wide range of food- and water-borne diseases in both humans and animals, thereby posing a major threat to public health. Recently, there has been an increasing number of reports, linking Salmonella contaminated raw vegetables and fruits with food poisoning. Many studies have shown that an essential feature of the pathogenicity of Salmonella is its capacity to cross a number of barriers requiring invasion of a large variety of cells and that the extent of internalization may be influenced by numerous factors. However, it is poorly understood how Salmonella successfully infects hosts as diversified as animals or plants. The aim of this review is to describe the different stages required for Salmonella interaction with its hosts: (i) attachment to host surfaces; (ii) entry processes; (iii) multiplication; (iv) suppression of host defense mechanisms; and to point out similarities and differences between animal and plant infections.
    Full-text · Article · Jan 2014 · Frontiers in Microbiology
  • Source
    • "Surprisingly, AHL have not been found in the intestinal tract of healthy mammals, with the exception of the bovine rumen (Erickson et al. 2002). SdiA from Salmonella could be activated in mice whose intestinal flora contained the AHLproducing Yersinia enterocolitica strain (Dyszel et al. 2010) or in turtle carrying Aeromonas hydrophila (Smith et al. 2008). After co-infection of mice with two S. Typhimurium strains engineered to produce AHL, a sdiA mutant and a sdiA + strain, it was shown that the constant activation of SdiA conferred a selective advantage to Salmonella (Dyszel et al. 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Salmonella enterica species includes about 2600 diverse serotypes, most of which cause a wide range of food- and water-borne diseases ranging from self-limiting gastroenteritis to typhoid fever in both humans and animals. Moreover, some serotypes are restricted to a few animal species, whereas other serotypes are able to infect plants as well as cold- and warm-blooded animals. An essential feature of the pathogenicity of Salmonella is its capacity to cross a number of barriers requiring invasion of a large variety of phagocytic and nonphagocytic cells. The aim of this review is to describe the different entry pathways used by Salmonella serotypes to enter different nonphagocytic cell types. Until recently, it was accepted that Salmonella invasion of eukaryotic cells required only the type III secretion system (T3SS) encoded by the Salmonella pathogenicity island-1. However, recent evidence shows that Salmonella can cause infection in a T3SS-1-independent manner. Currently, two outer membrane proteins Rck and PagN have been clearly identified as Salmonella invasins. As Rck mediates a Zipper-like entry mechanism, Salmonella is therefore the first bacterium shown to be able to induce both Zipper and Trigger mechanisms to invade host cells. In addition to these known entry pathways, recent data have shown that unknown entry routes could be used according to the serotype, the host and the cell type considered, inducing either Zipper-like or Trigger-like entry processes. The new paradigm presented here should change our classic view of Salmonella pathogenicity. It could also modify our understanding of the mechanisms leading to the different Salmonella-induced diseases and to Salmonella-host specificity.
    Full-text · Article · Sep 2012 · MicrobiologyOpen
  • Source
    • "A gene coding for a LuxR family protein (PpoR) has been identified in P. putida KT2440 (Subramoni and Venturi, 2009). Sequence analysis shows significant similarities between PpoR and SdiA, a regulator involved in interspecies cell–cell communication in Escherichia coli and Salmonella enterica (Van Houdt et al., 2006; Smith et al., 2008), and for which no cognate LuxI homologue has been identified. To test if the observed activation of ddcA expression by culture supernatants of P. aeruginosa could be mediated by PpoR, the reporter plasmid pME510 was introduced into the strain EU6, a ppoR mutant of KT2440 (Fernández-Piñar et al., 2011b) and b-galactosidase activity analysed both in liquid cultures and using the disc assay described above. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the identification of fatty acids as mediators of intercellular signalling in Pseudomonas putida, and between Pseudomonas aeruginosa and P. putida. Tetradecanoic acid and fatty acids of similar chain length are present in supernatants of these strains and activate population density-dependent expression of ddcA, a gene involved in corn seed and root colonization by P. putida KT2440. Consistently, significant amounts of these compounds were also found in corn root exudates. The signalling pathway involves the two-component regulatory system formed by RoxS and RoxR, which had been previously shown to control expression of ddcA and of a set of genes related to the redox balance of P. putida cells. Production of the fatty acid signal in P. aeruginosa is under the control of the LasI/LasR and RhlI/ RhlR quorum sensing systems. Our data indicate that in terms of cell–cell communication, P. putida KT2440 employs mechanisms closer to those of plant pathogens such as Xanthomonas spp. and fungi like Candida, which also rely on fatty acid derivatives.
    Full-text · Article · May 2012 · Environmental Microbiology Reports
Show more