Limits of propidium iodide as a cell viability indicator for environmental bacteria

Authors

  • Lei Shi,

    1. Department of Environmental Microbiology, UFZ, Helmholtz Centre for Environmental Research, Leipzig-Halle, 04318 Leipzig, Germany
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    • These authors contributed equally to this work.

  • Susanne Günther,

    1. Department of Environmental Microbiology, UFZ, Helmholtz Centre for Environmental Research, Leipzig-Halle, 04318 Leipzig, Germany
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    • These authors contributed equally to this work.

  • Thomas Hübschmann,

    1. Department of Environmental Microbiology, UFZ, Helmholtz Centre for Environmental Research, Leipzig-Halle, 04318 Leipzig, Germany
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  • Lukas Y. Wick,

    1. Department of Environmental Microbiology, UFZ, Helmholtz Centre for Environmental Research, Leipzig-Halle, 04318 Leipzig, Germany
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  • Hauke Harms,

    1. Department of Environmental Microbiology, UFZ, Helmholtz Centre for Environmental Research, Leipzig-Halle, 04318 Leipzig, Germany
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  • Susann Müller

    Corresponding author
    1. Department of Environmental Microbiology, UFZ, Helmholtz Centre for Environmental Research, Leipzig-Halle, 04318 Leipzig, Germany
    • Department of Environmental Microbiology, UFZ, Helmholtz Centre for Environmental Research Leipzig-Halle, Permoserstrasse 15, 04318 Leipzig, Germany
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  • Part of this manuscript was presented at the 11th Leipziger Workshop, April 27–29, 2006, BioCity Leipzig, Germany. Available at www.leipziger-workshop.de.

Abstract

Background:

Viability measurements of individual bacteria are applied in various scopes of research and industry using approaches where propidium iodide (PI) serves as dead cell indicator. The reliability of PI uptake as a cell viability indicator for dead (PI permeable) and viable (PI impermeable) bacteria was tested using two soil bacteria, the gramSphingomonas sp. LB126 and the gram+Mycobacterium frederiksbergense LB501T.

Methods:

Bacterial proliferation activities observed viaDAPI and Hoechst 33342 staining were linked to the energy charge and the proportion of dead cells as obtained by diOC6 (3)-staining and PI-uptake, respectively. Calibration and verification experiments were performed using batch cultures grown on different substrates.

Results:

PI uptake depended on the physiological state of the bacterial cells. Unexpectedly, up to 40% of both strains were stained by PI during early exponential growth on glucose when compared to 2–5% of cells in the early stationary phase of growth.

Conclusions:

The results question the utility of PI as a universal indicator for the viability of (environmental) bacteria. It rather appears that in addition to nonviable cells, PI also stains growing cells of Sphingomonas sp. and M. frederiksbergense during a short period of their life cycle. © 2007 International Society for Analytical Cytology

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