Impedance microbiology is a microbiological technique used to measure the microbial number density (mainly bacteria but also yeasts) of a sample by monitoring the electrical parameters of the growth medium. The ability of microbial metabolism to change the electrical conductivity of the growth medium was discovered by Stewart[1] and further studied by other scientists such as Oker-Blom,[2] Parson[3] and Allison[4] in the first half of 20th century. However, it was only in the late 1970s that, thanks to computer-controlled systems used to monitor impedance, the technique showed its full potential, as discussed in the works of Fistenberg-Eden & Eden,[5] Ur & Brown[6] and Cady.[7]
^Fistenberg-Eden, R.; Eden, G. (1984). Impedance Microbiology. New York: John Wiley.
^Ur, A.; Brown, D.F.J. (1975). Monitoring of bacterial activity by impedance measurements. New York: Chapter 5 in “New approaches to the identification of microorganisms”, edited by C. Heden & T. Illeni, John Wiley & Sons. pp. 63–71.
^Cady, P. (1978). Progress in impedance measurements in microbiology. Springfield: Chapter 14 in “Mechanizing microbiology” edited by Anthony N. Sharpe & David S. Clark, Charles C. Thomas Publisher. pp. 199–239.