title: Alterations of Escherichia coli envelope as a consequence of photosensitization with tetrakis(N-ethylpyridinium-4-yl)porphyrin tetratosylate.
abstract: Although several details of the photosensitization mechanisms involved in the photosensitized inactivation of bacteria have been elucidated, there are relatively few data on the morphological alterations induced on the bacterial cell structure during photosensitization. In this work we analysed the photodynamic action of the tetra-cationic photosensitizer tetrakis(N-ethylpyridinium-4-yl)porphyrin tetratosylate (TN-Et-PyP) on the integrity and selected functions of E. coli KMY1 cell membranes, in an effort to combine electron microscopy data with enzymatic assays and electrochemistry measurements. Using low concentrations of photosensitizer, damage is inflicted to the outer membrane and results in a higher permeability of the membrane to fairly small molecules such as deoxycholate; however, larger molecules such as periplasmic alkaline phosphatase are not released or are released after their extensive inactivation, as we could not register any enzyme activity outside the cells. Increasing the TN-Et-PyP concentration correlates with the inactivation of the respiratory chain, drop in plasma membrane voltage, the release of compounds with absorption band at 260 nm, and a decrease in intracellular enzyme β-galactosidase activity, though this activity has not been noticed to increase outside the cells, suggesting that enzyme inactivation probably occurs in inner cell districts.
authors.affiliation: Department of Biochemistry and Biophysics, Vilnius University, Vilnius, Lithuania. birute.pudziuvyte@gmail.com
authors.forename: Birute
authors.initials: B
authors.lastname: Pudziuvyte
authors.forename: Elena
authors.initials: E
authors.lastname: Bakiene
authors.forename: Raymond
authors.initials: R
authors.lastname: Bonnett
authors.forename: Pavel A
authors.initials: PA
authors.lastname: Shatunov
authors.forename: Michela
authors.initials: M
authors.lastname: Magaraggia
authors.forename: Giulio
authors.initials: G
authors.lastname: Jori
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000528:radiation effects; D055664:Electrochemical Techniques; D004926:Escherichia coli / Q000187:drug effects* / Q000528:radiation effects; D008027:Light; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000378:metabolism; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; C021096:tetra(4-N-methylpyridyl)porphine; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase