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Growth rate of rhizosphere bacteria measured directly by the tritiated thymidine incorporation technique

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Application of the tritiated-thymidine method for measurement of the in situ cell formation rate of rhizosphere bacteria was investigated. The growth of bacteria was observed in a sterilized soil-plant system. Viable or freeze-killed sterilized sugar beet seeds were coated with a strain of a fluorescent Pseudomonas and grown for 2-4 days in pots with sterilized soil. The pots were incubated with tritiated thymidine, the DNA extracted, and the amount of 3H in DNA measured, and quantified as number of bacteria formed per unit time. On the basis of the incorporation rate of tritiated thymidine and plate counts, specific growth rates were calculated. By use of the tritiated-thymidine method, a growth rate of 4.9 × 104 cells h-1 cm root-1 was obtained (generation time 106 h). Growth rates might be underestimated if thymidine is present in high concentrations in the soil or rhizosphere. Bacteria in the rhizosphere were responsible for 70% of the total bacterial growth in the pots. No significant 3H-labelling of plant root DNA was observed.

OriginalsprogEngelsk
TidsskriftSoil Biology and Biochemistry
Vol/bind21
Udgave nummer1
Sider (fra-til)113-117
ISSN0038-0717
DOI
StatusUdgivet - 1989

ID: 224286834