Detecting inactivated endospores in fluorescence microscopy using propidium monoazide

نویسندگان

  • Alexander Probst
  • Alexander Mahnert
  • Christina Weber
  • Klaus Haberer
  • Christine Moissl-Eichinger
چکیده

The differentiation between living and dead bacterial endospores is crucial in many research areas of microbiology. The identification of inactivated, non-pathogenic Bacillus anthracis spores is one reason why improvement of decontamination protocols is so desirable. Another field interested in spore viability is planetary protection, a sub-discipline of astrobiology that estimates the bioburden of spacecraft prior to launch in order to avoid interplanetary cross-contamination. We developed a dedicated, rapid and costeffective method for identifying bacterial endospores that have been inactivated and consequently show a compromised sporewall. This novel protocol is culture-independent and is based on fluorescencemicroscopy and propidiummonoazide (PMA) as a fluorescentmarker, which is suggested to bind to DNAof spores with compromised spore coat, cortex and membranes based on our results. Inactivated preparations (treated with wet heat, irradiation, ultracentrifugation) showed a significant increase in spores that were PMA stained in their core; moreover, Bacillus atrophaeus, Bacillus safensis and Geobacillus stearothermophilus seemed to be best suited for this technique, as the spore cores of all these endospores could be positively stained after inactivation. Lastly, we describe an additional counter-staining protocol and provide an example of the application of the coupled staining methods for planetary protection purposes. The introduction of this novel protocol is expected to provide an initial insight into the various possible future applications of PMA as a non-viability marker for spores in, for example, B. anthracis-related studies, food microbiology and astrobiology. Received 27 May 2011, accepted 13 December 2011, first published online 17 January 2012

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تاریخ انتشار 2012