The induction of filamentous growth in Escherichia coli by ruthenium and palladium complexes

Abstract

Cis-chloroammine complexes of platinum have been shown to induce several biological effects. These include induction of filamentous growth in Escherichia coli as well as induction of phage production from lysogenic strains of Escherichia coli. Cis-chloroammine complexes of platinum have also been proven effective as a treatment for several animal tumors. In general, the effectiveness of such compounds is determined by a combination of an internal polar nature coupled with an overall electrical neutrality. We have extended these studies to include other complexes of the group VIII elements. In the research reported here, complexes of ruthenium were shown to induce filamentous growth in E. coli. Cis-Ru(NH 3) 3Cl 3 produced this effect at a concentration of 6 μg/ml, comparable to the required concentration of cis-Pt(NH 3) 2Cl 2 for the same effect. The charged complex, K 2RuCl 5 · H 2O, induced filamentous growth but a significantly higher concentration of this ruthenium complex was necessary. Several palladium complexes were also tested. They proved to be toxic at relatively high concentrations and had no effect at lower concentrations. The proposed mechanism of action of the platinum complexes is the hydrolysis of two cis-chloride ligands followed by binding to DNA which reduces the synthesis of new DNA. The kinetic data on hydrolysis, the required cis-chloride ligands, electrical neutrality, and the selective action on various bacteria indicate that ruthenium and platinum interact by a similar mechanism.