HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Berney, M. Articles by Egli, T. Search for Related Content PubMed PubMed Citation Articles by Berney, M. Articles by Egli, T. Agricola Articles by Berney, M. Articles by Egli, T.

Flow-cytometric study of vital cellular functions in Escherichia coli during solar disinfection (SODIS)

Swiss Federal Institute of Aquatic Science and Technology (EAWAG), PO 611, CH-8600 Dübendorf, Switzerland

Correspondence
Thomas Egli
egli{at}eawag.ch

The effectiveness of solar disinfection (SODIS), a low-cost household water treatment method for developing countries, was investigated with flow cytometry and viability stains for the enteric bacterium Escherichia coli. A better understanding of the process of injury or death of E. coli during SODIS could be gained by investigating six different cellular functions, namely: efflux pump activity (Syto 9 plus ethidium bromide), membrane potential [bis-(1,3-dibutylbarbituric acid)trimethine oxonol; DiBAC₄(3)], membrane integrity (LIVE/DEAD BacLight), glucose uptake activity (2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose; 2-NBDG), total ATP concentration (BacTiter-Glo) and culturability (pour-plate method). These variables were measured in E. coli K-12 MG1655 cells that were exposed to either sunlight or artificial UVA light. The inactivation pattern of cellular functions was very similar for both light sources. A UVA light dose (fluence) of <500 kJ m^–2 was enough to lower the proton motive force, such that efflux pump activity and ATP synthesis decreased significantly. The loss of membrane potential, glucose uptake activity and culturability of >80 % of the cells was observed at a fluence of 1500 kJ m^–2, and the cytoplasmic membrane of bacterial cells became permeable at a fluence of >2500 kJ m^–2. Culturable counts of stressed bacteria after anaerobic incubation on sodium pyruvate-supplemented tryptic soy agar closely correlated with the loss of membrane potential. The results strongly suggest that cells exposed to >1500 kJ m^–2 solar UVA (corresponding to 530 W m^–2 global sunlight intensity for 6 h) were no longer able to repair the damage and recover. Our study confirms the lethal effect of SODIS with cultivation-independent methods and gives a detailed picture of the ‘agony’ of E. coli when it is stressed with sunlight.

This article has been cited by other articles:

				T. Juhna, D. Birzniece, S. Larsson, D. Zulenkovs, A. Sharipo, N. F. Azevedo, F. Menard-Szczebara, S. Castagnet, C. Feliers, and C. W. Keevil Detection of Escherichia coli in Biofilms from Pipe Samples and Coupons in Drinking Water Distribution Networks Appl. Envir. Microbiol., November 15, 2007; 73(22): 7456 - 7464. [Abstract] [Full Text] [PDF]

				M. Berney, F. Hammes, F. Bosshard, H.-U. Weilenmann, and T. Egli Assessment and Interpretation of Bacterial Viability by Using the LIVE/DEAD BacLight Kit in Combination with Flow Cytometry Appl. Envir. Microbiol., May 15, 2007; 73(10): 3283 - 3290. [Abstract] [Full Text] [PDF]