Catalase production influences germination,stress tolerance and virulence of Beauveria bassiana conidia

Catalases are the most important enzymatic systems used to degrade hydrogen peroxide (h 2o 2) into water and oxygen,thereby lowering intracellular hydrogen peroxide levels. entomopathogenic fungi display increased catalase activity during germination and growth,which is necessary to counteract the hyperoxidant state produced by oxidative metabolism. we studied the influence of five different hydrocarbons on catalase production by b. bassiana in order to determine the importance of catalase induction in fungal germination,stress tolerance and virulence. conidia produced by colonies grown on different carbon sources showed higher rates of catalase production compared to the control and the catalase activity of conidia produced on n-octacosane was four times catalase activity than the activity of the control. this increase in catalase activity was accompanied by a higher level of resistance to exogenous hydrogen peroxide and a reduction in the germination time. the higher expression of catalase also affected the virulence of b. bassiana. conidia from n-octacosane treatment proved most aggressive showing lowest st 50 value (5.49±0.34 days),and those from control treatment were the least virulent having st 50 value of 8.42±0.75 days. our study has helped to identify that over expression of the catalase improves the pathogenic ability of b. bassiana against plutella xylostella. copyright 2012 zoological society of pakistan.