Novel electrochemical sensors for clinical analysis.

determined in the range 3 x 108-2 x lo9 bacteria ml-' with a 2 a precision of 16%. The use of phenazine ethosulphate as a mediator in the work reported here was probably the main cause of greater sensitivity (6 x 106-6 x lo8 bacteria ml-I). This work has demonstrated that bioelectrochemical detectors, working in either the poised-potential or fuel-cell mode, can rapidly and reproducibly determine bacterial concentrations in the range of 106-108 bacteria. ml-l. Similar principles may be applied to the construction of broad-specificity whole-organism-based sensors, whereby the inhibition or stimulation of microbial activity is monitored electrochemically. Methylotrophic bacteria provide an ideal basis for such an instrument, being extremely stable and ca3able of oxidizing a wide range of organic substances (Higgins et al., 1980a). Their stimulation or inhibition should provide a valuable pollution monitor.