RESPONSE TO OXIDATIVE STRESS IN Candida tropicalis MEDIATED BY PHENOTYPIC SWITCHING EVENT

Phenotypic switching promotes reversible changes in colony morphology in Candida tropicalis. This species is an important opportunistic pathogen and infections caused by C. tropicalis usually cause high mortality rates. During infection, yeasts encounters a wide range of stress conditions from the host environment to which it adapts effectively, one of this stresses are oxidative stress, a tool used by host defense cells to cause damage and eliminate pathogens. The objective of the present study was to evaluate the resistance of phenotypic switching strains of C. tropicalis to oxidative stress. For this, two phenotypic switching systems (49.07 and 100.10) were used. This switching systems comprise, a parental morphotype (clinical strain – smooth colony), two structured phenotypic variants (Crepe and Rough) and two phenotypic revertants (Crepe revertant and Rough revertant - smooth colony). The morphotypes were exposed to 2 mM of hydrogen peroxide for 10 minutes and 60 minutes. After, cells were washed, diluted and spotted in YPD plates. Plates were incubated for 48 h at 28 °C and CFU was counted. For the late response to oxidative stress, morphotypes was plated in YPD supplemented with 2 mM of hydrogen peroxide. The quick response to oxidative stress was given by the ratio between exposed cells and non-exposed cells and the late response for the CFU in supplemented medium. Most part of the morphotypes exhibited sensitivity to oxidative stress exposition, Rough variant of 49.07, Crepe revertant of 100.10 and Crepe morphotypes of two systems, were not sensitivity after 10 minutes in stress condition, this variant show higher viability than the parental strain in both times and both switching systems analyzed. After 60 minutes, all morphotypes presented drastic reduction in cellular viability. In this time, smooth morphotyes and rough variant presented similar responses. The morphotypes did not presented growth capacity in stress condition after 96 hours of incubation. In this scenario, phenotypic switching promote the alteration of oxidative stress profile in 40 % of the morphotypes in short time exposition. Phenotypic switching event can mediate the emergence of the higher resistance to oxidative stress in short time individuals, this ability can promote changes in the stress tolerance and adaptation pathways, resulting in the key for the scape to the hostile environmental such as defense cells that has oxidative stress.