Soil buried mild steel corrosion by Bacillus cereus-SNB4 and its inhibition by Bacillus thuringiensis-SN8

Microbiologically influenced corrosion (mic) of mild steel coupons (mscs) under field simulated soil buried conditions was analysed up to exposure of 150 days. water and nutrient broth impregnated soil buried mscs were exposed to highly corrosive bacillus cereus-snb4,its non-corrosive antagonist bacillus thuringiensis-sn8 and their co-culture. after 50 days,mic rates of mscs treated with b. cereus-snb4 turned out to be 16.96 and 2.71 mg.dm -2.d -1 for wet and nutrient broth impregnated soils,respectively. after 100 days the corresponding values were 41.01 and 9.26 mg.dm -2.d -1,respectively. at the last observational point average percent weight losses due to mic of' the coupons exposed to the b. cereus-snb4 in wet and nutrient broth impregnated soils,were 32.89% and 1.83%,respectively. the reductions in mscs weights following exposure to b. thuringiensis-sn8 and the co-culture were found even lesser than those of the control coupons throughout the study period. mic inhibitory rather protective role of the bacterial antagonist is suggestive of secretion and involvement of some exoproduct(s) which made the mscs resistant to the bacterially accelerated corrosion. copyright 2011 zoological bociety of pakistan.