Rapid assessment of cell viability of Lactobacillus delbrueckii subsp. bulgaricus by measurement of intracellular pH in individual cells using fluorescence ratio imaging microscopy
Autor: | K. Björn Rechinger, Henrik Siegumfeldt |
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Rok vydání: | 2002 |
Předmět: |
Intracellular pH
Colony Count Microbial Industrial fermentation Carboxyfluorescein diacetate succinimidyl ester Microbiology Flow cytometry chemistry.chemical_compound Fluorescence microscope medicine Viability assay Chromatography Staining and Labeling medicine.diagnostic_test biology food and beverages General Medicine Hydrogen-Ion Concentration Flow Cytometry Fluoresceins biology.organism_classification Culture Media Lactobacillus Microscopy Fluorescence chemistry Biochemistry Fermentation Lactobacillus delbrueckii subsp. bulgaricus Food Science |
Zdroj: | International Journal of Food Microbiology. 75:53-60 |
ISSN: | 0168-1605 |
DOI: | 10.1016/s0168-1605(01)00745-0 |
Popis: | The aim of this study was to investigate if the measurement of intracellular pH (pH i ) of individual cells by fluorescence ratio imaging microscopy (FRIM) could be utilized as a rapid method for determining the bacterial viability, using Lactobacillus delbrueckii subsp. bulgaricus as a model organism. Five different standardized cultures with equal cell densities but varying viability were prepared on a trial-to-trial basis by combining aliquots of frozen and lyophilized cells with a 50-fold difference in viability, determined by the ability to form colonies on solid growth media. The acidification of milk and Acidification Power Test were used to determine the activity of these cultures. As expected, the cultures containing a higher proportion of viable cells acidified milk faster and performed better in the Acidification Power Test. All cells were fluorescent after staining with carboxyfluorescein diacetate succinimidyl ester but frozen cells reached higher fluorescence intensities than lyophilized cells. The number of strongly fluorescent cells determined by flow cytometry exceeded the number of viable cells determined by CFU. Analysis of pH i of individual cells by FRIM at an extracellular pH of 6.0 revealed two populations of cells with an average pH i of 6.9±0.1 and 6.1±0.1. As the number of cells maintaining a pH-gradient of 0.9±0.1 correlated well with CFU, we suggest that FRIM can be used as a rapid method for the determination of viability of L. delbrueckii subsp. bulgaricus . Measurement of pH i on a single cell basis is expected to provide accurate prediction of the fermentation performance in a wider range of industrial fermentation. |
Databáze: | OpenAIRE |
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