Abstract
The colorimetric identification of pathogenic and non-pathogenic bacteria in cell culture is commonly performed using the redox mediator N,N,N',N'-tetramethyl-para-phenylene-diamine (TMPD) in the so-called oxidase test, which indicates the presence of bacterial cytochrome c oxidases. The presented study demonstrates the ability of electrochemistry to employ TMPD to detect bacteria and quantify the activity of bacterial cytochrome c oxidases. Cyclic voltammetry studies and chronoamperometry measurements performed on the model organism Bacillus subtilis result in a turnover number, calculated for single bacteria. Furthermore, trace amounts of cytochrome c oxidases were revealed in aerobically cultured Escherichia coli, which to our knowledge no other technique is currently able to quantify in molecular biology. The reported technique could be applied to a variety of pathogenic bacteria and has the potential to be employed in future biosensing technology.