Inactivation of QS molecules by endophytic yeasts from sugar cane

BERTINI E; LEGUINA A; CASTELLANOS DE FIGUEROA, LUCÍA INÉS; NIETO PEÑALVER CG

Santiago de Compostela

Simposio; I International Symposium on Quorum Sensing inhibition. Research Advances on Quorum Sensing; 2015

Universidad de Santiago de Compostela

Quorum sensing (QS) enables the microorganisms to coordinate the gene expression inresponse to bacterial population density. QS involves the production of small signal moleculescalled autoinducers, being N-acyl homoserine lactones (AHLs) one of the most studied in Gramnegative bacteria. Quorum quenching (QQ) is a process in which the QS systems are disrupted through the inhibition of the signal production, its enzymatic inactivation or the interference of the receptor. Lactonases, acylases and oxidoreductases that inactivate AHLs have been isolated from both Prokaryotes and Eukaryotes. QQ is considered as a potential way in which microorganisms interfere with the QS signalization of others that share the same ecologicalniche. The function in nature of endophytic yeasts has remained largely obscure. In particular,the QQ properties of these fungal microorganisms have not been studied. The overall objectiveof this work was to characterize the ecological function of the QQ activities of endophytic yeastsisolated from sugarcane (Saccharum officinarum) in the interactions with both pathogenic andbeneficial bacteria. Three different genera of yeasts isolated from leaves, apoplastic andinternode tissues of the LCP 85-384 variety of sugarcane, the most utilized in the Northwest ofArgentina, showed AHL-inactivating activities. Among them, Rhodotorula sp. 7Apo1 wasselected for a further characterization. This strain presented both lactonase and acylase-likeenzymatic activities against both short- and long-chain AHLs. Cultivation of Rhodotorula sp.7Apo1 in media supplemented with different combinations of QS molecules, includingsubstituted and unsubstituted AHLs, showed that the presence of one molecule does notinterfere with the inactivation of the other. In cocultures with the phytopathogen P. syringae pv.syringae, the yeast Rhodotorula sp. 7Apo1 could inactivate the AHLs produced. An endophyticbacterium synthesizing at least two AHLs was isolated from sugarcane and identified asAgrobacterium sp. 6N2. The yeast Rhodotorula sp. 7Apo1 could also partially inactivate theAgrobacterium sp. 6N2 QS molecules. These results suggest that QQ activity from endophyticyeasts could play a remarkable role modulating the bacterial QS systems of microorganismscolonizing the same niche.