Characterization of the bactericidal effects of sodium nitroprusside and other pentacyanonitrosyl complexes on the food spoilage bacterium Clostridium sporogenes

• Published in: Applied and Environmental Microbiology 1998-09, Vol.64 (9), p.3195-3201
• Main Authors: Joannou, C.L. (King's College London, London, UK.), Cui, X.Y, Rogers, N, Vielotte, N, Martinez, C.L.T, Vugman, N.V, Hughes, M.N, Cammack, R
• Format: Article
• Language: English
• Subjects: Action of physical and chemical agents on bacteria; ANTIBACTERIAL PROPERTIES; ANTIMICROBIAL PROPERTIES; Bacteria; Bacteriology; Biological and medical sciences; Cell Fractionation; Cell Wall - drug effects; Cell Wall - ultrastructure; Cells; CLOSTRIDIUM; Clostridium - drug effects; Clostridium - growth & development; Clostridium - ultrastructure; Clostridium sporogenes; Culture Media; Dose-Response Relationship, Drug; Electron Spin Resonance Spectroscopy; Food contamination & poisoning; Food industries; Food Microbiology; Fundamental and applied biological sciences. Psychology; Microbiology; Microscopy, Electron; Nitroprusside - analogs & derivatives; Nitroprusside - pharmacology; PROPIEDADES ANTIMICROBIANAS; PROPRIETE ANTIMICROBIENNE; sodium nitroprusside; Time Factors; Toxicity
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.64.9.3195-3201.1998

The potent bactericidal activity of sodium nitroprusside (SNP; Na2[Fe(CN)5(NO)]) towards Clostridium sporogenes has been investigated. SNP inhibited cell growth in the concentration range of 10 to 40 micromolar. Concentrations above 80 micromolar caused irreversible loss of cell viability and cell lysis. Inhibition of cell growth was similar in complex and in defined media. SNP was found to be unreactive towards individual components of the defined medium, with the exception of cysteine. The chemical characteristics responsible for the potency of SNP were investigated by synthesizing analogs of SNP in which the Fe was replaced by different metals. The inhibitory potency of the pentacyanonitrosyl complexes decreased in the order Fe Cr V, which correlates with N-O stretching frequency (vNO). In contrast, the Ru complex which had a vNO comparable to that of Fe was a poor inhibitor. Electron paramagnetic resonance spectroscopy showed that SNP was rapidly reduced to the paramagnetic Fe(I) compound [Fe(CN)4(NO)]2- on contact with cells. Analysis of fractions from SNP-treated cells showed 90% oxidation of thiols in the cell walls compared with those in control cells. The toxicity of SNP involves S-nitrosation and reduction, the lack of toxicity of the Ru analog being consistent with the fact that it has poor reactivity towards thiols. When C. sporogenes cells were exposed to sublethal concentrations of SNP and viewed under the electron microscope, they showed blisters on the surface. These results point to the cell wall surface as a primary point of attack of the nitrosyl complex