A microcalorimetric study of the biologic effect of Mn(II) on Bacillus thuringiensis growth

A microcalorimetric technique based on the bacterial heat-output was explored to evaluate the effect of Mn(II) on Bacillus thuringiensis. The power-time curves of the growth metabolism of B. thuringiensis and the effect of Mn(II) on it were studied using an LKB-2277 BioActivity Monitor, ampoules method, at 28°C. For evaluation of the results, the maximum peak-heat output power (Pmax) in the growth phase, the growth rate constants (k), the log phase heat effects (Qlog ), and the total heat effect in 23 h (QT) for B. thuringiensis were determined. Manganese has been regarded as the essential biological trace element. Mn(II) of different concentration have different effects on B. thuringiensis growth metabolism. High concentration (800-1600 μg mL-1) of Mn(II) can promote the growth of B. thuringiensis; low concentration (500-800 μg mL-1) can inhabit its growth.