Quantitation of the Population Size and Metabolic Activity of a Resin Acid Degrading Bacterium in Activated Sludge Using Slot-Blot Hybridization to Measure the rRNA:rDNA Ratio |
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Authors: | AF Muttray WW Mohn |
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Institution: | (1) Department of Microbiology and Immunology, and Pulp and Paper Centre, University of British Columbia, #300-6174 University Boulevard, Vancouver, British Columbia, V6T 1Z3, Canada, CA |
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Abstract: | Abstract
The 16S rRNA:rDNA ratio is a useful parameter for measuring metabolic activity of a selected member of a complex microbial
community, as in pulp effluent activated sludge systems. The RNA:DNA ratio of Sphingomonas sp. DhA-33, previously isolated from a sequencing batch reactor treating pulp mill effluent, is positively correlated with
its growth rate (μ) under steady-state conditions. DhA-33 was grown in a chemostat with growth rates ranging from 0.04 to
0.15 cell divisions per hour. DhA-33 was also able to degrade dehydroabietic acid in bleached kraft mill effluent (BKME) plus
mineral medium in batch culture. Slot-blot hybridization with radioactively labeled species-specific oligonucleotide probes
for 16S rRNA and 16S rDNA was used to measure rRNA, rDNA, and the RNA:DNA ratio of this strain when in a mixed sludge community.
An increase in DhA-33 rDNA indicated growth of DhA-33 within the community. The RNA:DNA ratio of DhA-33 increased sharply
during exponential growth and declined as cells entered stationary phase. The RNA:DNA ratio decreased earlier and faster in
DhA- 33/sludge co-cultures than in DhA-33 pure cultures, presumably due to an earlier depletion of nutrients. The species-specific
quantification of the RNA:DNA ratio makes it possible to estimate the metabolic activity of selected members of a microbial
community in situ.
Received: 15 March 1999; Accepted: 8 July 1999; Online Publication: 15 February 2000 |
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