[Activities of superoxide dismutase in Xanthomonas oryzae pv. oryzae and its induction]

The activities of superoxide dismutase(SOD) in Xanthomonas oryzae pv. oryzae were determined to demonstrate the correlation of SOD activities with the bacterial virulence. In liquid culture, SOD activities of the tested strains reached the maxima at the end of lag phase and then declined. The virulent strain PXO99A showed higher SOD activities than the avirulent strain PXO99A (pBUavr Xa10.F1). Analysis on the subcellular location indicated that SOD activities detected from the cytoplasm and periplasm were over 70% and 20%-30% of the total, respectively. Treatment of the bacterial culture for 1 h with exogenous O2- at concentration of 50-800 mumol/L induced SOD activities of both the strains. The treatment with 200 mumol/L resulted in the highest SOD activities. The effect of exogenous O2- on SOD induction was more significant in 12 h-culture than in 24 h-culture, and more notable for the virulent strain PXO99A. The treatment with exogenous O2- resulted in significantly decreased survival rate off both the strains. The decreases of survival rate were greater in 24 h-culture than in 12 h-culture, and more significantly for the virulent strain than for the avirulent one.