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Acridine orange staining reaction as an index of physiological activity in Escherichia coliThe assumption that the acridine orange (AO) color reaction may be used as an index of physiological activity was investigated in laboratory grown Escherichia coli. Spectrofluorometric observations of purified nucleic acids, ribosomes and the microscopic color of bacteriophage-infected cells stained with AO confirmed the theory that single-stranded nucleic acids emit orange to red fluorescence while those that are double-stranded fluoresce green in vivo. Bacteria growing actively in a rich medium could be distinguished from cells in stationary phase by the AO reaction. Cells from log phase appeared red, whereas those in stationary phase were green. However, this differentiation was not seen when the bacteria were grown in a minimal medium or when a variation of the staining method was used. Also, shifting bacteria in stationary phase to starvation conditions rapidly changed their AO staining reaction. Boiling and exposure to lethal concentrations of azide and formalin resulted in stationary-phase cells that appeared red after staining but bacteria killed with chlorine remained green. These findings indicate that the AO staining reaction may be suggestive of physiological activity under defined conditions. However, variables in staining and fixation procedures as well as uncertainties associated with mixed bacterial populations in environmental samples may produce results that are not consistent with the classical interpretation of this reaction. The importance of validating the putative physiological implications of this staining reaction is stressed.
Document ID
20040088788
Acquisition Source
Johnson Space Center
Document Type
Reprint (Version printed in journal)
Authors
McFeters, G. A.
(Montana State University Bozeman)
Singh, A.
Byun, S.
Callis, P. R.
Williams, S.
Date Acquired
August 21, 2013
Publication Date
January 1, 1991
Publication Information
Publication: Journal of microbiological methods
Volume: 13
ISSN: 0167-7012
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: 1408001-G1493
CONTRACT_GRANT: NAG9-17346
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Number 04-10
NASA Discipline Environmental Health
Non-NASA Center

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