Document Detail


Use of a fluorescent redox probe for direct visualization of actively respiring bacteria.
MedLine Citation:
PMID:  1622256     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The redox dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) was employed for direct epifluorescent microscopic enumeration of respiring bacteria in environmental samples. Oxidized CTC is nearly colorless and is nonfluorescent; however, the compound is readily reduced via electron transport activity to fluorescent, insoluble CTC-formazan, which accumulates intracellularly. Bacteria containing CTC-formazan were visualized by epifluorescence microscopy in wet-mount preparations, on polycarbonate membrane filter surfaces, or in biofilms associated with optically opaque surfaces. Counterstaining of CTC-treated samples with the DNA-specific fluorochrome 4',6-diamidino-2-phenylindole allowed enumeration of active and total bacterial subpopulations within the same preparation. Municipal wastewater, groundwater, and seawater samples supplied with exogenous nutrients yielded CTC counts that were generally lower than total 4',6-diamidino-2-phenylindole counts but typically equal to or greater than standard heterotrophic (aerobic) plate counts. In unsupplemented water samples, CTC counts were typically lower than those obtained with the heterotrophic plate count method. Reduction of CTC by planktonic or biofilm-associated bacteria was suppressed by formaldehyde, presumably because of inhibition of electron transport activity and other metabolic processes. Because of their bright red fluorescence (emission maximum, 602 nm), actively respiring bacteria were readily distinguishable from abiotic particles and other background substances, which typically fluoresced at shorter wavelengths. The use of CTC greatly facilitated microscopic detection and enumeration of metabolically active (i.e., respiring) bacteria in environmental samples.
Authors:
G G Rodriguez; D Phipps; K Ishiguro; H F Ridgway
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  58     ISSN:  0099-2240     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  1992 Jun 
Date Detail:
Created Date:  1992-08-06     Completed Date:  1992-08-06     Revised Date:  2010-09-09    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1801-8     Citation Subset:  IM    
Affiliation:
Biotechnology Research Department, Orange County Water District, Fountain Valley, California 92728-8300.
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MeSH Terms
Descriptor/Qualifier:
Bacteria / isolation & purification,  metabolism*
Fluorescent Dyes
Kinetics
Microscopy, Fluorescence
Oxidation-Reduction
Oxygen Consumption
Tetrazolium Salts
Water Microbiology
Chemical
Reg. No./Substance:
0/Fluorescent Dyes; 0/Tetrazolium Salts; 102568-47-8/5-cyano-2,3-ditolyltetrazolium; 146-68-9/iodonitrotetrazolium
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