Biomolecules involved in the metabolism of Escherichia coli affected by photodynamics: A calorimetry study.

Antimicrobial resistance (AR) is a global health problem with significant consequences for the population and the economies of governments. In this context, several efforts are being made to investigate and develop alternative methods to counteract this situation, for example, photodynamic inactivation (PDI), which is a non-specific treatment to inhibit pathogenic microorganisms. It is based on the excitation of a photosensitizer molecule (PS) with UV-Vis radiation to generate reactive oxygen species (ROS), employing molecular oxygen already available in the environment. Due to their high reactivity, ROS produce oxidation of lipid membranes, proteins, and nucleic acids, eventually leading to cell death. Despite the fact that multiple works have been carried out using PDI, the investigation about the structural changes induced in the biomolecules of microorganisms that lead to cell inactivation has been limited. In the present work, we used differential scanning calorimetry (DSC) to study the thermodynamic changes produced by PDI in E. coli. We showed that such changes are correlated with the loss of viability and metabolic processes.