tailieunhanh - Báo cáo khoa học: Are UV-induced nonculturable Escherichia coli K-12 cells alive or dead?

Cells that have lost the ability to grow in culture could be defined operationally as either alive or dead depending on the method used to determine cell viability. As a conse-quence, the interpretation of the state of nonculturable cells is often coliK12 cells inactivated by UV-irradiation with a low (UV1) and a high (UV2) dose wereusedas amodel of nonculturable cells. Cells inactivated by the UV1 dose lost culturability but they were not lysed andmaintained the capacity to respond to nutrient addition by protein synthesis and cell wall synthesis. . | Eur. J. Biochem. 270 2689-2695 2003 FEBS 2003 doi Are UV-induced nonculturable Escherichia coliK-12 cells alive or dead Andrea Villarino1 2 Marie-Noelle Rager3 Patrick A. D. Grimont1 2 and Odile M. M. Bouvet2 1 Aquabiolab and 2Unite de Biodiversité des Bactéries Pathogenes Emergentes INSERM U389 Institut Pasteur Paris France 3Service de Resonance Magnetique Nucleaire UMR 7576 Ecole Nationale Superieure de Chimie de Paris France Cells that have lost the ability to grow in culture could be defined operationally as either alive or dead depending on the method used to determine cell viability. As a consequence the interpretation of the state of nonculturable cells is often ambiguous. Escherichia coli K12 cells inactivated by UV-irradiation with a low UV1 and a high UV2 dose were used as a model of nonculturable cells. Cells inactivated by the UV1 dose lost culturability but they were not lysed and maintained the capacity to respond to nutrient addition by protein synthesis and cell wall synthesis. The cells also retained both a high level of glucose transport and the capacity for metabolizing glucose. Moreover during glucose incorporation UV1-treated cells showed the capacity to respond to aeration conditions modifying their metabolic flux through the Embden-Meyerhof and pentose-phosphate pathways. However nonculturable cells obtained by irradiation with the high UV2 dose showed several levels of metabolic imbalance and retained only residual metabolic activities. Nonculturable cells obtained by irradiation with UV1 and UV2 doses were diagnosed as active and inactive dying cells respectively. Keywords NMR radiation injury viability metabolism Escherichia coli. Ultraviolet irradiation has been used in the disinfection of drinking water wastewater and in air disinfection 1-3 . After disinfection microorganisms are not detectable in standard culture media in which they have been previously found to proliferate 4 . Thus a bacterium is .