Adaptation to UVA radiation of E. coli growing in continuous culture

Michael Berney, Hans Ulrich Weilenmann, Thomas Egli

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Adaptive responses of bacteria to physical or chemical stresses in the laboratory or in the environment are of great interest. Here we investigated the ability of Escherichia coli growing in continuous culture to adapt to UVA radiation. It was shown that E. coli indeed expressed an adaptive response to UVA irradiation at an intensity of 50 W/m2. Cells grown in continuous culture with complex medium (diluted Luria Bertani broth) at dilution rates of 0.7 h-1, 0.5 h-1 and 0.3 h-1 were able to maintain growth under UVA irradiation after a transient reduction of specific growth rate and recovery. In contrast, slow-growing cells (D = 0.05 h-1) were unable to induce enough protection capacity to maintain growth under UVA irradiation. We propose that faster growing E. coli cells have a higher adaptive flexibility to UVA light-stress than slow-growing cells. Furthermore it was shown with flow cytometry and viability stains that at a dilution rate of 0.3 h-1 only a small fraction (≤1%) of the initial cell population survived UVA light-stress. Adapted cells were significantly larger (30%) than unstressed cells and had a lower growth yield. Furthermore, efflux pump activity was diminished in adapted cells. In a second irradiation period (after omitting UVA irradiation for 70 h) adapted cells were able to trigger the adaptive response twice as fast. Additionally, this study shows that continuous cultivation with direct stress application allows reproducible investigation of the physiological and possibly also molecular mechanisms during adaptation of E. coli populations to UVA light.

Original languageEnglish (US)
Pages (from-to)149-159
Number of pages11
JournalJournal of Photochemistry and Photobiology B: Biology
Issue number2
StatePublished - Feb 1 2007
Externally publishedYes


  • Adaptation
  • Continuous culture
  • E. coli
  • Resistance
  • Solar disinfection (SODIS)
  • UVA light

ASJC Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging


Dive into the research topics of 'Adaptation to UVA radiation of E. coli growing in continuous culture'. Together they form a unique fingerprint.

Cite this