Cadmium toxicity in Escherichia coli: Cell morphology, Z-ring formation and intracellular oxidative balance.

This article deals with toxicological study of cadmium (Cd) as CdCl(2) on the growth and cell morphology of Escherichia coli K-12 MG1655. The minimum inhibitory concentration of Cd was 15μM. When cadmium was added at mid-log phase, growth was completely inhibited at 0.6mM and 50% of the bacterial growth retardation was found at 0.3mM concentration. At sublethal dose of Cd (0.2mM), majority of the cells showed filamentous form, suggested the possible effect of Cd on cell division. AFM study of bacterial cell morphology revealed severe surface damage of the treated cells in comparison to untreated cells. The expression of FtsZ decreased both at transcriptional and translational levels with the time of Cd exposure, thus cell division was affected and as a result cells took filamentous form. Due to Cd exposure, the nucleoid segregation remained unaffected, but improper Z-ring formation was observed. Activities of peroxidase and superoxide dismutase significantly decreased in treated cells with exposure time, which might elevate intracellular ROS level, as a consequence metabolic dysfunction and toxic effect were resulted.