Content area
Full Text
J Ind Microbiol Biotechnol (2008) 35:14471454 DOI 10.1007/s10295-008-0446-2
ORIGINAL PAPER
Photodynamic inactivation of recombinant bioluminescent Escherichia coli by cationic porphyrins under artiWcial and solar irradiation
Eliana Alves Carla M. B. Carvalho Joo P. C. Tom Maria A. F. Faustino Maria G. P. M. S. Neves Augusto C. Tom Jos A. S. Cavaleiro ngela Cunha Snia Mendo Adelaide Almeida
Received: 18 March 2008 / Accepted: 30 July 2008 / Published online: 20 August 2008 Society for Industrial Microbiology 2008
Abstract A faster and simpler method to monitor the photoinactivation process of Escherichia coli involving the use of recombinant bioluminescent bacteria is described here. Escherichia coli cells were transformed with luxCDABE genes from the marine bioluminescent bacterium Vibrio Wscheri and the recombinant bioluminescent indicator strain was used to assess, in real time, the eVect of three cationic meso-substituted porphyrin derivatives on their metabolic activity, under artiWcial (40 W m2) and solar irradiation (t620 W m2). The photoinactivation of bioluminescent E. coli is eVective (>4 log bioluminescence decrease) with the three porphyrins used, the tricationic porphyrin Tri-Py+-Me-PF being the most eYcient compound. The photoinactivation process is eYcient both with solar and artiWcial light, for the three porphyrins tested. The results show that bioluminescence analysis is an eYcient and sensitive approach being, in addition, more aVordable, faster, cheaper and much less laborious than conventional methods. This approach can be used as a screening method for bacterial photoinactivation studies in vitro and also for the monitoring of the eYciency of novel photosensitizer
molecules. As far as we know, this is the Wrst study involving the use of bioluminescent bacteria to monitor the antibacterial activity of porphyrins under environmental conditions.
Keywords Cationic porphyrins Photodynamic antimicrobial therapy Bioluminescence Escherichia coli Solar irradiation
Introduction
The growing reduction of water resources due to environmental pollution has become a major public health concern. Thus, wastewater treatment and disinfection is even more necessary at large scale. The inactivation of pathogenic microorganisms, in the last stage of wastewater treatment, can be achieved by several techniques such as chlorination, ozonation and ultraviolet radiation. To overcome the high costs and the diYculty in implementing these techniques, alternative physico-chemical methods have been studied, namely the photodynamic antimicrobial therapies [13]. This somewhat new technique uses a light source (sunlight or artiWcial...