Bacterial quorum sensing molecules modify the oxidative stress response in the endophytic yeast Meyerozyma guilliermondii 6N

ELISA V. BERTINI; ANA CAROLINA LEGUINA; BARRIOS, ANDREA CECILIA; LUCÍA I. CASTELLANO DE FIGUEROA; JEAN-MICHEL CAMADRO; CARLOS G. NIETO PEÑALVER

San Miguel de Tucumán

Congreso; XII Congreso Argentino de Microbiología General; 2017

Sociedad Argentina de Microbiología General

It has been largely described that quorum sensing (QS) systems,regulatory mechanisms whose activities are related to the cell density of thepopulation, play key roles in the regulation of the microbial physiology. Throughthe production and release of signal molecules, the cell senses the density ofthe population and modifies its physiology accordingly, repressing or inducinggenes. It is well known that QS signal molecules have also an important effecton the host. However, up to date little is known about the effect of thesecompounds on the physiology of fungi that can colonize the same niche than theproducing bacterium. To analyze this aspect, we characterized the response tobacterial QS molecules of Meyerozyma guilliermondii6N, endophitic yeast isolated from sugarcane. Noteworthy, this plant is also colonizedby bacteria harbouring active QS systems. Considering what has been describedin plant and mammal cells, we focused in the modification of the oxidativestress response of the yeast by the QS molecules. M. guilliermondii 6N was cultivated aerobically in complex mediumsupplemented independently with 12 different AHLs (C6-HSL, 3OC6-HSL, C8-HSL, 3OC8-HSL,3OHC8-HSL, C10-HSL, 3OC10-HSL, 3OHC10-HSL, C12-HSL, 3OC12-HSL and 3OHC12-HSL)and the oxidative stress response to different compounds was analyzed by flowcytometry. The detection of dying cells was evaluated after staining withpropidium iodide (PI), while the oxidative stress was analyzed through thedetection of reactive oxygen species (ROS) with the fluorescent probes dihydrorhodamine123 (DHR123), dihydroethidium (DHE) and dihydrofluorescein diacetate (DHFDA). Resultsobtained show that under the assayed conditions, the levels of ROS induced by diamide,menadione or cadmium were not modified by any of the AHLs assayed. However, measurementsperformed with DHE showed that a group of AHLs, in particular those with a longacyl chain (i. e., C12-HSL, 3OC12-HSL and 3OHC12-HSL), augment the levels ofROS induced by tert-butylhydroperoxide, an alkyl hydroperoxide, in M.guilliermondii 6N, suggesting increased levels of superoxide anion. TheseAHLs also increased the level of dying cells of M. guilliermondii 6N, as determined with IP. Noteworthy, theobserved responses (higher levels of ROS and dying cells) were directly relatedto the concentrations of the AHLs. These findings show that the response of theendophytic yeast M. guilliermondii tospecific stressors is affected by the presence of certain AHLs. Themodification of the fungal physiology by these quorum sensing molecules also suggeststhat the biological activity of AHLs is broader than previously known.