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

BERTINI ELISA VIOLETA; CASTELLANOS DE FIGUEROA LUCÍA INÉS; ANA CAROLINA LEGUINA; CAMADRO JEAN-MICHEL; BARRIOS ANDREA; NIETO PEÑALVER CARLOS GABRIEL

san miguel de tucuman

Congreso; XII Congreso argentino de microbiología general SAMIGE.; 2017

SAMIGE

It has been largely described that quorum sensing (QS) systems, regulatory mechanisms whose activities are related to the cell density of the population, play key roles in the regulation of the microbial physiology. Through the production and release of signal molecules, the cell senses the density of the population and modifies its physiology accordingly, repressing or inducing genes. It is well known that QS signal molecules have also an important effect on the host. However, up to date little is known about the effect of these compounds on the physiology of fungi that can colonize the same niche than the producing bacterium. To analyze this aspect, we characterized the response to bacterial QS molecules of Meyerozyma guilliermondii 6N, endophitic yeast isolated from sugarcane. Noteworthy, this plant is also colonized by bacteria harbouring active QS systems. Considering what has been described in plant and mammal cells, we focused in the modification of the oxidative stress response of the yeast by the QS molecules. M. guilliermondii 6N was cultivated aerobically in complex medium supplemented 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 flow cytometry. The detection of dying cells was evaluated after staining with propidium iodide (PI), while the oxidative stress was analyzed through the detection of reactive oxygen species (ROS) with the fluorescent probes dihydrorhodamine 123 (DHR123), dihydroethidium (DHE) and dihydrofluorescein diacetate (DHFDA). Results obtained 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, measurements performed with DHE showed that a group of AHLs, in particular those with a long acyl chain (i. e., C12-HSL, 3OC12-HSL and 3OHC12-HSL), augment the levels of ROS induced by tert-butyl hydroperoxide, an alkyl hydroperoxide, in M. guilliermondii 6N, suggesting increased levels of superoxide anion. These AHLs also increased the level of dying cells of M. guilliermondii 6N, as determined with IP. Noteworthy, the observed responses (higher levels of ROS and dying cells) were directly related to the concentrations of the AHLs. These findings show that the response of the endophytic yeast M. guilliermondii to specific stressors is affected by the presence of certain AHLs. The modification of the fungal physiology by these quorum sensing molecules also suggests that the biological activity of AHLs is broader than previously known.