Evaluation of ferricyanide effects on microorganisms with multi-methods

In this study, we report the effects of ferricyanide on organisms based on the changes in physiological state and morphology of Escherichia coli (E coli) DH 5 alpha after being pretreated by ferricyanide. The impact on bacterial cell growth and viable rate of exposure to different concentrations of ferricyanide was determined, and the morphology change of E. coli was studied by atomic force microscopy (AFM). Finally, recovery test was used to evaluate the recovery ability of injured cells. The results showed that the effects on growth and morphology of E. coli were negligible when the concentration of ferricyanide was below 25.0 mM. While the results showed 50.8% inhibition of growth in the presence of 50.0 mM ferricyanide for 3 h, 89.6% viability was detected by flow cytometry (FCM) assay. AFM images proved that compact patches appeared on the bacterial surface and protected the bacterial viability. Furthermore, the results revealed that deterioration of bacterial surface closely related to the incubation time from 0.5 to 3 h at 100.0 mM ferricyanide. In the recovery test, microbial cell population and dissolved oxygen individually decreased 36.7% and 28.3% with 25.0 mM ferricyanide. These results clearly demonstrated that ferricyanide indeed affected viability of cells than morphology damaged, and the effects of toxin on bacteria were not reversible. (C) 2008 Elsevier B.V. All rights reserved.