Online Monitoring of Bacterial Growth with an Electrical Sensor

Herein, we developed an automatic electrical bacterial growth sensor (EBGS) based on a multichannel capacitively coupled contactless conductivity detector (C⁴D). With the use of the EBGS, up to eight culture samples of E. coli in disposable tubes were online monitored simultaneously in a noninvasive manner. Growth curves with high resolution (on the order of a time scale of seconds) were generated by plotting normalized apparent conductivity value against incubation time. The characteristic data of E. coli growth (e.g., growth rate) obtained here were more accurate than those obtained with optical density and contact conductivity methods. And the correlation coefficient of the regression line ( r) for quantitative determination of viable bacteria was 0.9977. Moreover, it also could be used for other tasks, such as the investigation of toxic/stress effects from chemicals and antimicrobial susceptibility testing. All of these performances required neither auxiliary devices nor additional chemicals and biomaterials. Taken together, this strategy has the advantages of simplicity, accuracy, reproducibility, affordability, versatility, and miniaturization, liberating the users greatly from financial and labor costs.