IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Tolerance to oxidative stress and its relationship with triacylglycerol accumulation by actinobacteria
Autor/es:
BEQUER URBANO, SUSANA; CORTEZ, NÉSTOR; FARIAS, MARIA EUGENIA; ÁLVAREZ, HÉCTOR
Lugar:
Mar del Plata
Reunión:
Congreso; VIII Congreso de Microbiología General - SAMiGe 2012; 2012
Institución organizadora:
Sociedad Argentina de Microbiología General SAMiGe
Resumen:
Andean Altiplano and semiarid Patagonia, are both characterized by their extremeenvironmental conditions, such as desiccation. The frequent occurrence of actinobacteria may reflect their natural adaptation to these environments. Oxidative stress, which is a consequence of desiccation, is one of the main factors occurring in these habitats. These bacteria need to adjust their metabolism to survive under oxidative stress. The aim of this work was to analyze the tolerance of Rhodococcus bacteria to oxidative stress and the relationship between triacylglycerol (TAG) accumulation and the response to pro-oxidants, since both are NADPH-consuming processes. Sensitivity to H2O2 or methyl viologen (MV) in seven strains was analyzed in agar plates. Rhodococcus opacus PD630 was used as model for analyzing the relationship between TAG metabolism and the response to oxidative stress.Cells were cultivated in mineral salts medium (MSM) with gluconate and 0.1 g/l of ammonium chloride to promote lipid accumulation. Incubation of cells in MSM in the absence of a carbon source was used for promoting lipid mobilization. Cerulenin and Orlistat were used for inhibiting fatty acid and TAG biosynthesis, and TAG mobilization, respectively. Lipids were analyzed by thin layer chromatography and spectrometry.All actinobacteria were more resistant to H2O2 and MV in NB agar than Gram negativebacteria isolated from Altiplano. All showed similar tolerance to H2O2, whereas R. opacus PD630, R. jostii 602, and Dietzia sp. A12 were the more resistant strains to MV. Since NADPH is the reductant of several enzymes involved in antioxidant activities, and also required for TAG biosynthesis; we analyzed the alteration of the cell response to pro-oxidants during TAG accumulation conditions, with/without cerulenin. Cells of PD630 showed high survival rates during exposition to H2O2 and MV under TAG accumulation conditions, with and without cerulenin. However, TAG content decreased in cells treated with MV, but not with H2O2, in the absence of cerulenin. TAG degradation may generate NADPH for protective/antioxidant activities. To analyze this, we challenge cells to H2O2 and MV in the presence/absence of Orlistat. The inhibition of TAG degradation had no effect on cell survival during treatment with H2O2 and MV, compared with controls.The results indicated that actinobacteria are highly tolerant to oxidative stress, which can explain in part their resistance to desiccation. The response to H2O2 and O2-, generated by MV, may require a differential adjustment of metabolism. The response of cells to O2- , but not to H2O2, may compete for reductants with other NADPH-demanding processes, such as TAG accumulation. Thus, preservation of NADPH is advantageous during stress response. Moreover, stress response did not seem to depend on TAG degradation for generating reductants for repair and/or antioxidant mechanisms.