Preliminary Study of the Application of Dynamic Speckle Pattern Analysis for Toxicants Detection Based on Bacterial Motility Changes

This paper presents a preliminary study of the application of dynamic laser speckle (biospeckle) to evaluate bacterial mobility in liquid medium. This technique, a proven tool to evaluate the temporal evolution of different phenomena, allows us to identify qualitative differences in bacterial mobility caused by the presence of different contaminants in the liquid medium where they are found. We worked with a defined concentration of mobile bacteria (Pseudomonas aeruginosa), which were exposed to different contaminants. Sterile physiological solution (culture diluent) and bacterial culture without toxic addition were used as controls. Each sample was individually transilluminated in a petri dish with a HeNe laser (20mw and 632.8 nm wavelength) expanded and attenuated from the bottom through a ground-glass diffuser. Videos were obtained at different times that were then processed with Shannon’s Entropy algorithm, obtaining pseudocolored images that indicate the level of activity/mobility of the sample. Preliminary results were obtained that indicate the potential of the technique and this bacterium as a bioindicator and will allow progress towards the development of a fast and high-resolution biosensor, which could have various applications in health, environment and food quality control.