AUTHOR=Huedo Pol , Yero Daniel , Martínez-Servat Sònia , Ruyra Àngels , Roher Nerea , Daura Xavier , Gibert Isidre 

TITLE=Decoding the genetic and functional diversity of the DSF quorum-sensing system in Stenotrophomonas maltophilia

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00761

DOI=10.3389/fmicb.2015.00761

ISSN=1664-302X

ABSTRACT=<p><italic>Stenotrophomonas maltophilia</italic> uses the Diffusible Signal Factor (DSF) quorum sensing (QS) system to mediate intra- and inter-specific signaling and regulate virulence-related processes. The components of this system are encoded by the <italic>rpf</italic> cluster, with genes <italic>rpfF</italic> and <italic>rpfC</italic> encoding for the DSF synthase RpfF and sensor RpfC, respectively. Recently, we have shown that there exist two variants of the <italic>rpf</italic> cluster (<italic>rpf</italic>-1 and <italic>rpf</italic>-2), distinguishing two groups of <italic>S. maltophilia</italic> strains. Surprisingly, only <italic>rpf</italic>-1 strains produce detectable DSF, correlating with their ability to control biofilm formation, swarming motility and virulence. The evolutive advantage of acquiring two different <italic>rpf</italic> clusters, the phylogenetic time point and mechanism of this acquisition and the conditions that activate DSF production in <italic>rpf</italic>-2 strains, are however not known. Examination of this cluster in various species suggests that its variability originated most probably by genetic exchange between rhizosphere bacteria. We propose that <italic>rpf</italic>-2 variant strains make use of a strategy recently termed as “social cheating.” Analysis of cellular and extracellular fatty acids (FAs) of strains E77 (<italic>rpf</italic>-1) and M30 (<italic>rpf</italic>-2) suggests that their RpfFs have also a thioesterase activity that facilitates the release of unspecific FAs to the medium in addition to DSF. Production of DSF in <italic>rpf</italic>-1 strains appears in fact to be modulated by some of these extracellular FAs in addition to other factors such as temperature and nutrients, while in <italic>rpf-2</italic> strains DSF biosynthesis is derepressed only upon detection of DSF itself, suggesting that they require cohabitation with DSF-producer bacteria to activate their DSF regulatory machinery. Finally, we show that the mixed <italic>rpf</italic>-1/<italic>rpf</italic>-2 population presents synergism in DSF production and virulence capacity in an <italic>in vivo</italic> infection model. Recovery and quantification of DSF from co-infected animals correlates with the observed mortality rate.</p>