DNA synthesis and tritiated thymidine incorporation by heterotrophic freshwater bacteria in continuous culture

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · Applied and Environmental Microbiology; (United States)

OSTI ID:5382486

Ellenbroek, F M; Cappenberg, T E ^[1]

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1. Limnological Inst., Nieuwersluis (Netherlands)

Continuous cultivation of heterotrophic freshwater bacteria was used to assess the relationship between DNA synthesis and tritiated thymidine incorporation. In six different continuous cultures, each inoculated with a grazer-free mixed bacterial sample from Lake Vechten (The Netherlands), tritiated thymidine incorporation into a cold trichloroacetic acid precipitate and bacterial cell production were measured simultaneously. Empirical conversion factors were determined by division of both parameters. They ranged from 0.25 {times} 10{sup 18} to 1.31 {times} 10{sup 18} cells mol of tritiated thymidine{sup {minus}1}. In addition, DNA concentrations were measured by fluorometry with Heochst 33258. The validity of this technique was confirmed. Down to a generation time of 0.67 day, bacterial DNA content showed little variation, with values of 3.8 to 4.9 fg of DNA cell{sup {minus}1}. Theoretical conversion factors, which can be derived from DNA content under several assumptions, were between 0.26 {times} 10{sup 18} and 0.34 {times} 10{sup 18} cells mol of thymidine{sup {minus}1}. Isotope dilution was considered the main factor in the observed discrepancy between the conversion factors. In all experiments, a tritiated thymidine concentration of 20 nM was used. It was concluded that the observed difference resulted from intracellular isotope dilution which cannot be detected by current techniques for isotope dilution analysis.

• OSTI ID: 5382486
• Journal Information: Applied and Environmental Microbiology; (United States), Journal Name: Applied and Environmental Microbiology; (United States) Vol. 57:6; ISSN 0099-2240; ISSN AEMID
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540311* -- Environment
Aquatic-- Basic Studies-- Radiometric Techniques-- (1990-)
AZINES
BACTERIA
CONTINUOUS CULTURE
DNA REPLICATION
FRESH WATER
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
MICROORGANISMS
NUCLEIC ACID REPLICATION
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PYRIMIDINES
RIBOSIDES
THYMIDINE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
UPTAKE
WATER