Proof-of-concept bioelectrochemical characterization of Mycolicibacterium smegmatis for diagnostic applications

Elevated urease activity in tuberculosis-infected individuals is often suggestive of bacterial virulence by promoting survivability and establishment of the causative pathogen (Mycobacterium tuberculosis) in the host. Thus, heightened urease activity could be a promising biomarker for screening pathogenic mycobacterial strains. In this proof-of-concept study, we evaluate the suitability of electrochemical techniques for direct screening of mycobacterial strains based on urease activity. Mycolicibacterium smegmatis wildtype (WT), a derived knockout mutant of the LCP protein family (∆0107) with high urease activity, and its complement strain (c-0107) were coated in polydopamine (PDA) and immobilized on a screen-printed electrode (SPE) for microscopy and electrochemical characterization, in presence of exogenous redox mediators: potassium ferricyanide, anthraquinone, and riboflavin. Microscopy showed compatibility of PDA as a coating material for mycobacterial cells. Electrochemical analysis results indicated enhanced M. smegmatis electroactivity in the presence of anthraquinone, with higher current output in the strain with high urease activity. Experiments at different urea concentrations suggest that urea is not required for this screening approach. This work shows that electrochemical data can potentially distinguish mycobacterial strains based on urease activity. It also lays a groundwork in the model mycobacteria M. smegmatis, which could facilitate development of assays for pathogenic mycobacterial species.