Impedance microbiology

Silley P. Forsythe S. (1996) Impedance microbiology—a rapid change for microbiologists. JBacterial 80, 233-243. 

The concept of impedance microbiology is more than a century old however, it gained its popularity only in the mid-seventies. Impedance is based on the changes in conductance in a medium due to the microbial breakdown of inert substrates into electrically charged ionic compounds and acidic by-products. The detection time, that is, the time necessary for... 

Glassmoyer, K. E., and Russell, S. M. (2001). Evaluation of a selective broth for detection of Staphylococcus aureus using impedance microbiology. /. Food Prot. 64, 44-50. 

A review of the diverse food hygiene applications of impedance microbiology has recently been published [243]. The detection of Enterohacteriaceae, particularly Salmonella spp., the determination of total bacterial counts, and the examination of antibiotics and food additives for an-timicrobiological effects are important. Another short review describes a model explaining the effects of microbial growth and metabolism on capacitance at electrodemedium interfaces [244]. 

R. Gomez-Sjoberg, D.T. Morisette, R. Bashir, Impedance microbiology-on-a-chip microfluidic bioprocessor for rapid detection of bacterial metabolism. Journal of Micro-electromechanical Systems 14 (4) (August 2005) 829-838. 

C. J. Felice, M. E. Valentinuzzi, Medium and interface components in impedance microbiology. IEEE Transactions on Biomed. Eng., 1999,46, pp. 1483-1487. 

Currently available methods for determining seafood freshness have been reviewed (2,3,4,5). In general, sensory and microbiological quality of seafoods are the standards most often utilized for determining freshness. There are, however, several limitations with these methods such as the need for trained technicians, problems with subjectivity, or long analysis times. Consequently, several new methods have been proposed using chemical indices of freshness that attempt to overcome these difficulties. The purpose of the present paper is to first review these methods with particular emphasis on shrimp freshness determinations and, secondly, to present experimental evidence showing that impedance can be used to denote shrimp freshness. 

Oil is another problem. Even small traces of oil can reduce chemical inhibitor performance and impede heat transfer. Therefore it must be eliminated. It is always preferable to remove microbiological organisms, oil, and other forms of organic contaminants from a water source prior to its use as cooling system makeup. 

However, a dictionary definition of fouling includes to obstruct (with foreign matter), to entangle, to impede, while a foulant is described as fetid, stinking, and putrid. Thus the definition of foulant should, of necessity, include matter of microbiological origin, plus its degradation products. 

One line in bioelectrochemistry is rooted in electrochemical techniques, spectroscopy, and other physical chemical techniques. Linear and cyclic voltammetry are central.Other electrochemical techniques include impedance and electroreflectance spectroscopy," ultramicro-electrodes, and chronoamperometry. To this come spectroscopic techniques such as infiared, surface enhanced Raman and resonance Raman,second harmonic generation, surface Plasmon, and X-ray photoelectron spectroscopy. A second line has been to combine state-of-the-art physical electrochemistry with corresponding state-of-the-art microbiology and chemical S5mthesis. The former relates to the use of a wide range of designed mutant proteins, " the latter to chemical synthesis or de novo designed synthetic redox metalloproteins. " " ... 

G Th Kroyer, K Futschik. The impedance-splitting method for microbiologic analysis of food preservatives. Biotech. Lab. 2 8-10. 1997. 

J. Wissenwasser, M.J. Vellekoop, and R. Heer, Signal Generator for Wireless Impedance Monitoring of Microbiological Systems, IEEE Transactions on Instrumentation and Measurement, vol. 60, no. 6, pp. 2039-2046, 2011. 

Fig. 6 Equivalent circuit representation of a typical impedance cell used in microbiology. The symbols R, and Q represent the interfacial resistances and capacitances, respectively, while Rm is the resistance of the medium separating the two electrodes. 

At present, four companies provide specialized impedance measurement instrumentation for chnical microbiology or food hygiene applications. BioMirieux manufactures the Bactometer, which can monitor conductance, capacitance, or impedance in up to two temperature-controlled incubators, each containing 256 samples. Malthus Instruments produces... 

Under aerobic conditions, areas under respiring colonies can become anodic and surrounding areas cathodic. A thick biofilm can prevent diffusion of oxygen to cathodic sites and diffusion of aggressive anions, such as chlorides to anodic sites. Outward diffusion of metabolites and corrosion products also is impeded. If areas within the biofilm become anaerobic, the cathodic mechanism can change to reduction of water or microbiologically produced H2S. 

Johnston, M. D. and Jones, M. V., 1995. Disinfection tests with intact biofilms combined use of the Modified Robbins Device with impedance detection. Journal of Microbiological Methods 21, 15-26. 

D. Miranda, S. Jaimes, J. Bastidas. (2014) Assessment of carbon steel microbiologically induced corrosion by electrical impedance spectroscopy. Journal Solid State Electrochemistry, vol. 18, pp. 389-398. 

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