Redox potential-dependent nitrite metabolism by Salmonella typhimurium

Abstract

Salmonellae are generally resistant to the inhibitory effects of NaNO2. Removal of the lipopolysaccharide of Salmonella typhimurium by ethylenediaminetetraacetic acid pretreatment did not result in subsequent inhibtion of growth by NaNO2, indicating that lipopolysaccharide does not function to exclude NaNO2 from the cell. NaNO2 disappeared from the medium while the cells were growing, but, after stationary phase was reached, no further losses were observed unless the pH was maintained above 7.0. Similar losses were observed in a cell-free system if the redox potential of the medium was between -250 and -175 mV. If the disrupted cell suspension was first heated in a boiling water bath for 15 to 18 min, no NaNO2 loss was observed regardless of the redox potential. S. typhimurium is capable of metabolizing NaNO2, possibly by means of a nitrite-reducing enzyme function which is redox controlled.