Toxicity Effect of Pb(II) on Two Different Kinds of Microbes Measured by Microcalorimetry
In this work, microcalorimetric technique was used to analyze Pb(II) toxic action on the metabolic activities of Candida humicola and Bacillus subtilis. The experimental results revealed that Pb(II) had a stimulating effect on C. humicola and B. subtilis growth at a relatively low concentration (10.0 g·mL−1); while, C. humicola and B. subtilis were inhibited completely when the concentrations were up to 320.0 and 160.0 g·mL−1, respectively, and the relationships between growth rate constant (k) and doses of Pb(II) were approximately linear for the two microbes at certain concerntrations. At the same time, their cell dry weight and turbidity (OD600) during growth were also obtained. Their thermogenic curves of the growth coincided well with their turbidity curves, elucidating that the microcalorimetric method agreed with the routine microbiology methods. All of these corroborate the validity and sensitivity of the microcalorimetric technique to investigate the toxic effect of Pb(II) on soil microorganisms.