Microcalorimetric study of Escherichia coli growth inhibited by the selenomorpholine complexes

The inhibitory or antibiotic action of four kinds of the selenomorpholine c omplex on a strain of Escherichia coli was studied by microcalorimetry. Dif ferences in their capacities to inhibit the metabolism of this bacterium we re observed. The extent and duration of the inhibitory effect on the metabo lism as judged from the rate constant, k, and the half-inhibitory concentra tion, IC50, varied with the different drugs. The rate constant (k) of Esche richia coli (in the log phase) in the presence of the drugs decreased with increasing concentrations of the drugs (C). The relationship of k and C is nearly linear for (1) selenomorpholine and (2) selenomorpholine hydrochlori de, but for (3) N,N'-methylene bisselenomorpholine and (4) N-dodecyl seleno morpholine, it is not linear. The experimental results reveal that the sequ ence of antibiotic activity of selenomorpholines is (3) and (4) > (1) > (2) .