IQUIBICEN   23947
INSTITUTO DE QUIMICA BIOLOGICA DE LA FACULTAD DE CIENCIAS EXACTAS Y NATURALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Induction of KatA and KatB Activity by Exposure to Low UVA Doses in Pseudomonas aeruginosa: Role Against Subsequent Higher Doses and Other Stress Factors.
Autor/es:
PEZZONI, M.; TRIBELLI, PM; PIZARRO, R.; LÓPEZ, N.I.; COSTA, C.
Reunión:
Congreso; ASM Conference on Pseudomonas; 2015
Resumen:
Pseudomonas aeruginosa is a versatile bacterium able to adapt to a wide range of stress factors including solar UVA radiation. High UVA doses produce lethal effects due to the action of reactive oxygen species (ROS). To defend itself against ROS, P. aeruginosa has several strategies, including the H2O2-inducible KatA and KatB catalases; previously, we demonstrated that KatA is essential in the defense against high UVA doses. Exposure to low UVA doses also induces oxidative damage but, in addition, it produces an inhibition of growth without loss of viability, mechanism proposed as an adaptive strategy to face high UVA doses. In order to characterize this phenomenon, we investigated the effect of low UVA doses on the regulation of KatA and KatB and its physiological consequences. The wild-type PAO1 and isogenic katA and katB derivatives were grown under sublethal UVA doses (fluence rate 25 W/m2) or in the dark. Exposure to UVA induced total catalase activity of PAO1 and katB strains in about 25%. Assays with non-denaturing polyacrylamide gels demonstrated that both KatA and KatB activities were increased by the radiation. Results obtained with transcriptional fusions demonstrated that UVA increased the transcription of katA (2- fold) and katB (1.3-fold); RT-qPCR analysis confirmed this result. ROS scavengers were added to the irradiation medium to analyze the role of specific ROS on katA and katB transcription. Catalase and sodium pyruvate (scavengers of H2O2) decreased transcription of both genes in irradiated cultures to values similar to dark controls; on the contrary, mannitol and DMSO (scavengers of hydroxyl radical and superoxide, respectively) did not affect their expression under UVA. To analyze the role of KatA and KatB induction on the response to subsequent oxidative stresses, control and pre-exposed bacteria were submitted to lethal doses of UVA, sodium hypochlorite or H2O2. Exposure to low UVA produced a protective effect against lethal UVA or hypochlorite that depends on induction of katA or katB, respectively; on the contrary, other factors are involved in protection against lethal doses of H2O2. In summary, the results indicate that exposure of P. aeruginosa to low UVA doses induces KatA and KatB activity at transcriptional level. This phenomenon represents a protective mechanism against subsequent oxidative stress factors.