Profiling electric signals of electrogenic probiotic bacteria using self-attention analysis

We fabricated a self-assembled electric circuit to detect the electrical signals produced by two electrogenic probiotic bacteria [Leuconostoc mesenteroides (L. mesenteroides) and Lactococcus lactis (L. lactis)] on chicken egg chorioallantoic membranes as well as in the intestine lumen of mice. Inoculation of L. mesenteroides or L. lactis plus glucose onto a ferrozine assay triggered the reduction of ferric ions to ferrous ions and the formation of ferrozine complexes, indicating the bacterial electron production. In the presence of glucose, L. lactis yielded higher electricity, measured by voltage changes, than L. mesenteroides in vitro. The spectra of the electrical signals generated by these two probiotic bacteria were highly distinguishable. We evaluated the importance of these differences with the application of a self-attention mechanism, a deep learning-based module, revealing several unique signals in the electrical spectra of L. mesenteroides as well as L. lactis bacteria. The specific electrical spectrum for each probiotic bacterium provided a dynamic signature for evaluation of the efficacy of various therapies using probiotics, antibiotics, and fecal microbiota transplantation in the future. KEY POINTS: • The electrical signals produced by probiotic bacteria L. mesenteroides and L. lactis on chicken egg chorioallantoic membranes and in the mouse intestine lumen were detectable. • In the presence of glucose, L. lactis yielded higher electricity than L. mesenteroides in vitro. Furthermore, the electrical spectra generated by these two bacteria were different. • The importance of these differences with the application of a self-attention mechanism revealed several unique signals in the electrical spectra.