IQUIBICEN   23947
INSTITUTO DE QUIMICA BIOLOGICA DE LA FACULTAD DE CIENCIAS EXACTAS Y NATURALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Induction of Kat A and Kat B Activity by Exposure to Low UVA Doses in Pseudomonas aeruginosa: Role Against subsequent Higher Doses and Other Stres Factors
Autor/es:
PEZZONI MAGDALENA; TRIBELLI PAULA M.; PIZARRO RAMON; LOPEZ NANCY I; COSTA CRISTINA S.
Reunión:
Conferencia; ASM Conference on Pseudomonas; 2015
Institución organizadora:
ASM
Resumen:
Pseudomonas aeruginosa is a versatile bacteriumable to adapt to a wide range of stress fac-135Poster AbstractsASM Conference on Pseudomonastors including solar UVA radiation. High UVAdoses produce lethal effects due to the actionof reactive oxygen species (ROS). To defenditself against ROS, P. aeruginosa has severalstrategies, including the H2O2-inducible KatAand KatB catalases; previously, we demonstratedthat KatA is essential in the defenseagainst high UVA doses. Exposure to low UVAdoses also induces oxidative damage but, inaddition, it produces an inhibition of growthwithout loss of viability, mechanism proposedas an adaptive strategy to face high UVAdoses. In order to characterize this phenomenon,we investigated the effect of low UVAdoses on the regulation of KatA and KatB andits physiological consequences. The wild-typePAO1 and isogenic katA and katB derivativeswere grown under sublethal UVA doses (fluencerate 25 W/m2) or in the dark. Exposure toUVA induced total catalase activity of PAO1and katB strains in about 25%. Assays withnon-denaturing polyacrylamide gels demonstratedthat both KatA and KatB activities wereincreased by the radiation. Results obtainedwith transcriptional fusions demonstrated thatUVA increased the transcription of katA (2-fold) and katB (1.3-fold); RT-qPCR analysisconfirmed this result. ROS scavengers wereadded to the irradiation medium to analyzethe role of specific ROS on katA and katBtranscription. Catalase and sodium pyruvate(scavengers of H2O2) decreased transcriptionof both genes in irradiated cultures to valuessimilar to dark controls; on the contrary, mannitoland DMSO (scavengers of hydroxylradical and superoxide, respectively) did notaffect their expression under UVA. To analyzethe role of KatA and KatB induction on theresponse to subsequent oxidative stresses, controland pre-exposed bacteria were submittedto lethal doses of UVA, sodium hypochlorite orH2O2. Exposure to low UVA produced a protectiveeffect against lethal UVA or hypochloritethat depends on induction of katA or katB,respectively; on the contrary, other factors areinvolved in protection against lethal doses ofH2O2. In summary, the results indicate that exposureof P. aeruginosa to low UVA doses in duces KatA and KatB activity at transcriptionallevel. This phenomenon represents a protectivemechanism against subsequent oxidative stressfactors.