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Appl. Environ. Microbiol., Nov 1995, 3981-3985, Vol 61, No. 11
S Selvaratnam, BA Schoedel, BL McFarland and CF Kulpa
A modified freeze-thaw method in combination with reverse transcriptase PCR
was developed for monitoring gene expression in activated sludge. The
sensitivity of the methodology was determined by inoculating non- sterile
activated sludge samples with 3-chlorobenzoate-degrading Pseudomonas putida
PPO301(pRO103), which contains the catabolic tfdB gene. tfdB mRNA was
detected in 10 mg of activated sludge inoculated with 10(4) CFU of the
target organism. This technique was subsequently utilized to analyze the in
situ expression of the catabolic dmpN gene in a sequencing batch reactor
(SBR) bioaugmented with phenol-degrading P. putida ATCC 11172. Greatest
dmpN expression was observed 15 min after maximum phenol concentration was
reached in the reactor and 15 min after the start of aeration. Decreased
phenol concentrations in the reactor corresponded to reduced levels of dmpN
expression, although low levels of dmpN mRNA were observed throughout the
SBR cycle. These results indicate that concentration of phenol in the
reactor and the onset of aeration stimulated transcriptional activity of
the dmpN gene. The information obtained from this study can be used to
alter SBR operational strategies so as to lead to more effective
bioaugmentation practices.
Copyright © 1995, American Society for Microbiology
Application of reverse transcriptase PCR for monitoring expression of the catabolic dmpN gene in a phenol-degrading sequencing batch reactor
Department of Biological Sciences, University of Notre Dame, Indiana 46556, USA.
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