This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Donkersloot, J. A. Articles by Krichevsky, M. I. Search for Related Content PubMed Articles by Donkersloot, J. A. Articles by Krichevsky, M. I. Agricola Articles by Donkersloot, J. A. Articles by Krichevsky, M. I.

 Previous Article  |  Next Article 

Appl Environ Microbiol. 1972 August; 24(2): 179-183
Copyright © 1972 American Society for Microbiology. All Rights Reserved.

Fluorometric Determination of Deoxyribonucleic Acid in Bacteria with Ethidium Bromide

¹ Environmental Mechanisms Section, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20014

ABSTRACT

A simple, sensitive, and rapid method is presented for the determination of deoxyribonucleic acid (DNA) in both gram-positive and gram-negative bacteria. It is based upon the fluorometric determination of DNA with ethidium bromide after alkaline digestion of the bacteria to hydrolyze the interfering ribonucleic acid. The assay takes less than 2 hr. Its sensitivity is at least 0.2 µg of DNA in a final solution of 4 ml and it uses commonly available filter or double monochromator fluorometers. Judicious choice of light source and filters allows an additional 10-fold increase in sensitivity with a filter fluorometer. Turbidity caused by bacteria or insoluble polysaccharides does not interfere with the fluorescence measurements. There was no significant difference between the results obtained with this method and those obtained with the indole and diphenylamine methods when these assays were applied to Escherichia coli and sucrose- or glucose-grown Streptococcus mutans. The method was also tested by determining the specific growth rate of E. coli. This new procedure should be especially useful for the determination of bacterial DNA in dilute suspensions and for the estimation of bacterial growth or DNA replication where more conventional methods are not applicable or sensitive enough.