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[Methyl‐3H]thymidine macromolecular incorporation and lipid labeling: Their significance to DNA labeling during measurements of aquatic bacterial growth rate
Author(s) -
Robarts Richard D.,
Wicks Richard J.
Publication year - 1989
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1989.34.1.0213
Subject(s) - macromolecule , thymidine , chemistry , dna , ethanol , biochemistry , chromatography , hydrolysis , dna synthesis , labelling
It is essential during measurements of aquatic bacterial production with [methyl#x2010; 3 H]thymidine (Tdr) that only labeled DNA is measured. We found in 12 freshwater and marine systems that DNA labeling represented a variable proportion of total macromolecular labeling. Up to 87% of label appearing in precipitated labeled macromolecules from acid#x2010;base hydrolysis treatments was soluble in ethanol. Reverse#x2010;phase, high#x2010;pressure liquid chromatography showed that the composition of labeled molecules in the ethanol was 78–88% [ 3 H]Tdr. The rate of labeling of the ethanol#x2010;soluble fraction was significantly correlated with the rate of total macromolecular labeling ( r = 0.88, n = 40, P < 0.001) and less strongly with the DNA labeling rate ( r = 0.49, n = 28, P = 0.005). Experiments in which bacterial cells were labeled with [ 3 H]Tdr or 32 PO 4 3− showed that above a total macromolecular labeling rate of ∼1 pmol Tdr liter −1 h −1 , bacterial cells bind Tdr but do not incorporate it into phospholipids in the cell envelope.