Study of thermokinetic properties of sodium selenite on Bacillus thuringiensis Cry B by microcalorimetry

By using an LKB2277 Bioactivity Monitor, the power-time curves of Bacillus thuringiensis Cry B at 28 degreesC effected by Na2SeO3 were determined. Som e parameters, such as growth rate constants k, inhibitory ratio I, the maxi mum heat production rate P-max, heat output Q, were obtained. Considering b ath the growth rate constant k and heat output Q, we found that a low conce ntration of Na2SeO3 had a promoting action on the growth of Bacillus thurin giensis Cry B, but a high concentration of Na2SeO3 had an inhibitory action . The toxicity of a toxicant tan also be expressed as half inhibitory conce ntration IC50 of toxicant, i.e., 50% effective in this inhibition. The valu e of IC50 Of Na2SeO3 on Bacillus thuringiensis Cry B is 117 mug/mL. This mi crocalorimetric bioassay for cellular toxicity is based on metabolic heat e volution from cultured cells. The assay is quantitative, inexpensive, and v ersatile.