Photodynamic Inactivation of Escherichia coli
Antibiotic resistance is an increasing problem in the treatment of bacterial infections. A good alternative to antibiotics is the photodynamic inactivation (PDI): Killing microorganism with light. The principle idea is simple. Combining a photosensitizer, light with the appropriate wavelength to excite it and molecular oxygen leads to the generation o
f toxic reactive oxygen species (ROS). In our group we want to characterize different Escherichia coli K12 mutants of the Keio collection (Collection of nearly 4000 single gene knock-out mutants of all non-essential genes) to answer the following questions:
1. Localization of photosensitizer
Microscopy suggests that the photosensitizer is associated to the surface of the bacteria. But during the genome-wide screening of the Keio collection transport proteins result hypersensitive against PDI which indicates an intracellular localization of the photosensitizer. Further test are planned to analyze it in detail.
2. Killing effects
The results of the screening give a hint that DNA and protein damage play a role during photodynamic inactivation and we want to examine this result.
3. Identification of possible resistance mechanism against PDI
Another aim of our group is to identify possible protection mechanism of E. coli against PDI. The bacteria have different systems to protect themselves from ROS. coli can export the photosensitizer rapidly via the strong TolC-efflux system. Other part is the detoxification of the reactive oxygen species by Superoxide Dismutase and Catalase enzymes.
