Microcalorimetric Study of the Biological Effects of Zn2+ on Bacillus thuringiensis Growth

A microcalorimetric technique was used to investigate the influence of Zn 2+ on the growth metabolism of Bacillus thuringiensis . LKB 2277 Bioactivity Monitor was employed to obtain the power time curves, from which the maximum peak heat output power ( P max ) in the log phase, the growth rate constants ( k ), the inhibitory ratios ( I ), the generational time ( t G) and the total heat effect ( Q total ) in 23 h for the growth metabolism of Bacillus thuringiensis at 28 ℃ can be evaluated. The results indicate that the concentration of Zn 2+ affects its growth obviously. Low concentration (0-50 μg/mL) of Zn 2+ promotes the growth of Bacillus thuringiensis while high concentration (50-500 μg/mL) of Zn 2+ inhibits its growth. When the concentration reached up to 600 μg/mL, it can not grow at all.