%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Ahlgren, N. A.
%A Harwood, C. S.
%A Schaefer, A. L.
%A Giraud, Eric
%A Greenberg, E. P.
%T Aryl-homoserine lactone quorum sensing in stem-nodulating photosynthetic bradyrhizobia
%D 2011
%L fdi:010053508
%G ENG
%J Proceedings of the National Academy of Sciences of the United States of America
%@ 0027-8424
%K bacterial communication ; LuxI-LuxR homologs ; sociomicrobiology
%M ISI:000289888500093
%N 17
%P 7183-7188
%R 10.1073/pnas.1103821108
%U https://www.documentation.ird.fr/hor/fdi:010053508
%> https://www.documentation.ird.fr/intranet/publi/2011/05/010053508.pdf
%V 108
%W Horizon (IRD)
%X Many Proteobacteria possess LuxI-LuxR-type quorum-sensing systems that produce and detect fatty acyl-homoserine lactone (HSL) signals. The photoheterotroph Rhodopseudomonas palustris is unusual in that it produces and detects an aryl-HSL, p-coumaroyl-HSL, and signal production requires an exogenous source of p-coumarate. A photosynthetic stem-nodulating member of the genus Bradyrhizobium produces a small molecule signal that elicits an R. palustris quorum-sensing response. Here, we show that this signal is cinnamoyl-HSL and that cinnamoyl-HSL is produced by the LuxI homolog BraI and detected by BraR. Cinnamoyl-HSL reaches concentrations on the order of 50 nM in cultures of stem-nodulating bradyrhizobia grown in the presence or absence of cinnamate. Acyl-HSLs often reach concentrations of 0.1-30 mu M in bacterial cultures, and generally, LuxR-type receptors respond to signals in a concentration range from 5 to a few hundred nanomolar. Our stem-nodulating Bradyrhizobium strain responds to picomolar concentrations of cinnamoyl-HSL and thus, produces cinnamoyl-HSL in excess of the levels required for a signal response without an exogenous source of cinnamate. The ability of Bradyrhizobium to produce and respond to cinnamoyl-HSL shows that aryl-HSL production is not unique to R. palustris, that the aromatic acid substrate for aryl-HSL synthesis does not have to be supplied exogenously, and that some acyl-HSL quorum-sensing systems may function at very low signal production and response levels.
%$ 084