QUORUM SENSING INHIBITORS IN LEGUME-ASSOCIATED BACTERIA

FIORELA L. NIEVAS; LUCIANA VILCHEZ; PABLO C. BOGINO; WALTER GIORDANO

Congreso; XII Congreso Argentino de Microbiología General; 2017

Quorum sensing (QS) systems use N-acyl-homoserine lactones (AHLs) as signaling molecules, commonlyfound in Gram-negative bacteria that live in association with plants. QS system allows bacteria to functionas multicellular organisms, because the extracellular concentration of autoinducer increases with bacteriapopulation growth, after attaining a determinate number. Presently, QS mechanisms are considered as apotential novel target for the study of bacteria-plant interactions. Arachis hypogaea L. (peanut) constitutesan important legume crop with high relevance at different agroecological areas worldwide. Peanutestablishes a nitrogen-fixing symbiosis with genetically diverse rhizobia grouped as Bradyrhizobium sp.. Inthis work, we analyzed the QS mechanisms used by rhizobia with special emphasis on the advances relatedto QS inhibitors produced by legume and bacteria. For that purpose, the bacterial biosensor strains, wereemployed for the different assays. In order to determine QS inhibitors molecules in bacteria and peanutsmaterials, inverse assays were carried out. Inhibition test of short and long acyl chain were performedby adding C6-HSL or C12-AHL, respectively. QS inhibition assay with biosensor strains demonstrated thatlegume and bacteria inhibited the expression of short and long homoserine lactones mediated phenotypes,suggesting a possible degradative activity for AHL in these extracts. In addition, Bradyrhizobium sp. P8A,a native strain isolated from peanut nodules, in contact with the biosensor strain and in absence of theplant was capable of producing AHLs with long acyl chains. Since that the synthesis of these AHLs by theP8A strain is only reached at the interface medium-air and not in the entire medium, we were able todemonstrate the production of inhibitors of QS molecules in strains capable of moving to the air interfacewould be linked to the aerobic behavior of this bacteria. We are currently in the process of identifyingof AHL-lactonase activity. So far, our results indicate that in our experimental work model, legume andrhizobacteria are capable of communicating among themselves to coordinate group responses in order toadapt their physiology to environmental factors.