Superoxide dismutases and glutaredoxins have a distinct role in the response of Candida albicans to oxidative stress generated by the chemical compounds menadione and diamide

To cope with oxidative stress, Candida albicans possesses several enzymes involved in a number of biological processes, including superoxide dismutases (Sods) and glutaredoxins (Grxs). The resistance of C. albicans to reactive oxygen species is thought to act as a virulence factor. Genes such as SOD1 and GRX2, which encode for a Sod and Grx, respectively, in C. albicans are widely recognised to be important for pathogenesis. We generated a double mutant, Δgrx2/sod1, for both genes. This strain is very defective in hyphae formation and is susceptible to killing by neutrophils. When exposed to two compounds that generate reactive oxygen species, the double null mutant was susceptible to menadione and resistant to diamide. The reintegration of the SOD1 gene in the null mutant led to recovery in resistance to menadione, whereas reintegration of the GRX2 gene made the null mutant sensitive to diamide. Despite having two different roles in the responses to oxidative stress generated by chemical compounds, GRX2 and SOD1 are important for C. albicans pathogenesis because the double mutant Δgrx2/sod1 was very susceptible to neutrophil killing and was defective in hyphae formation in addition to having a lower virulence in an animal model of systemic infection

Igneous garnet and amphibole fractionation in the roots of island arcs: experimental constraints on andesitic liquids

To evaluate the role of garnet and amphibole fractionation at conditions relevant for the crystallization of magmas in the roots of island arcs, a series of experiments were performed on a synthetic andesite at conditions ranging from 0.8 to 1.2 GPa, 800-1,000 degrees C and variable H2O contents. At water undersaturated conditions and fO(2) established around QFM, garnet has a wide stability field. At 1.2 GPa garnet ? amphibole are the high-temperature liquidus phases followed by plagioclase at lower temperature. Clinopyroxene reaches its maximal stability at H2O-contents <= 9 wt% at 950 degrees C and is replaced by amphibole at lower temperature. The slopes of the plagioclase-in boundaries are moderately negative in T-XH2O space. At 0.8 GPa, garnet is stable at magmatic H2O contents exceeding 8 wt% and is replaced by spinel at decreasing dissolved H2O. The liquids formed by crystallization evolve through continuous silica increase from andesite to dacite and rhyolite for the 1.2 GPa series, but show substantial enrichment in FeO/MgO for the 0.8 GPa series related to the contrasting roles of garnet and amphibole in fractionating Fe-Mg in derivative liquids. Our experiments indicate that the stability of igneous garnet increases with increasing dissolved H2O in silicate liquids and is thus likely to affect trace element compositions of H2O-rich derivative arc volcanic rocks by fractionation. Garnet-controlled trace element ratios cannot be used as a prox