Generation of reactive oxygen species by Candida albicans in relation to morphogenesis

Candida albicans is able to generate significant amounts of reactive oxygen species (ROS). In this study, ROS generation by yeast and hyphal forms of the strain 3153 A was analyzed to determine whether ROS generation could be a major factor in the invasive behavior of germinative cells. Furthermore, the virulent strain CA6 and its avirulent and agerminative mutant VIR3 wer e compared, ROS were measured by lucigenin-enhanced chemiluminescence and a cytochrome c assay. During the blastoconidial phase of all strains moderat e amounts of ROS were found at cell concentrations >1 x 10(5)/ml. However, ROS generation appeared to be specifically inhibited at cell concentrations >1 x 10(8)/ml, and this was found in both assays. As shown in comparative experiments, the medium used for measurement markedly affected the total am ount of ROS. Hyphae of strain 3153 A generated a significantly higher amoun t of ROS than yeast cells and cells with germ tubes (P < 0.001). The strain CA6 showed significantly higher ROS generation than the VIR3 strain for bo th blastoconidiae and after 30 min of induction of hypha formation (P < 0.0 5). In conclusion, hypha formation, usually acknowledged as a major factor in Candida pathogenicity, was associated with markedly increased ROS format ion. ROS generation was not closely linked to the ability to form hyphae, b ut was highest in germinative cells.