Microcalorimetrical Study of the Effect of Selenium and Cadmium on the Growth Metabolism of Escherichia coli

Abstract

A microcalorimetric technique was used to evaluate the influence of Se (selenium morpholine) and Cd²⁺ [Cd(NO₃)₂] on Escherichia coli growth. By means of 3114/3236 TAM Air isothermal calorimeter, ampoule method at 37 ºC, the thermogenic curves of E. coli growth were obtained under different conditions. In order to analyze the results, the maximum power P_m and the growth rate constants k were determined, which showed that values of P_m and k were linked to the concentration of Se and Cd²⁺. The results showed that a low concentration of Se (1-10 μg/mL) promoted the growth of E. coli and a high concentration of Se (> 10 μg/mL) inhibited the growth, but the Cd²⁺ is always inhibiting the growth of E. coli. However, there was an antagonistic or positive synergistic effect of Se and Cd²⁺ on E. coli when Se was 1-4 μg/mL and Cd²⁺ was 1-3 μg/mL. There was a negative synergistic effect of Se and Cd²⁺ on E. coli when Se was higher than 4 μg/mL and Cd²⁺ was higher than 3 μg/mL. The effect of Se and Cd²⁺ on E. coli was related to the formation of the Se-Cd complex compounds under different conditions chosen.