Detection system for Legionella bacteria using photogate-type optical sensor

This study describes a bacterial sensing system using a photogate-type fluorescence sensor for the purpose of identifying Legionella bacteria, which are known to emit different fluorescence for each bacterial species when irradiated with UV excitation light. First a weak-photocurrent measurement system in combination with a photogate-type optical sensor and a circuit board which was mounted with a current-voltage converter, an analog-to-digital converter, and a microcomputer was fabricated. Then weak-light measurement was performed by simulating the bacterial fluorescence of Legionella. A difference in the current ratio generated in the sensor was found depending on the wavelength of the LED light source, showing that the system works as a spectrometer. Finally, the system was applied to measure the fluorescence of the species of Legionella dumoffii and Legionella erythra and each species of Legionella was identified just by obtaining the current ratio.