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Applied and Environmental Microbiology, July 2007, p. 4550-4558, Vol. 73, No. 14
0099-2240/07/$08.00+0     doi:10.1128/AEM.00169-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Transcriptome Analysis Reveals that Multidrug Efflux Genes Are Upregulated To Protect Pseudomonas aeruginosa from Pentachlorophenol Stress{triangledown}

Jocelyn Fraga Muller,1,{dagger} Ann M. Stevens,2 Johanna Craig,3 and Nancy G. Love1,2*

Department of Civil and Environmental Engineering,1 Department of Biological Sciences,2 Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 240613

Received 23 January 2007/ Accepted 20 May 2007

Through chemical contamination of natural environments, microbial communities are exposed to many different types of chemical stressors; however, research on whole-genome responses to this contaminant stress is limited. This study examined the transcriptome response of a common soil bacterium, Pseudomonas aeruginosa, to the common environmental contaminant pentachlorophenol (PCP). Cells were grown in chemostats at a low growth rate to obtain substrate-limited, steady-state, balanced-growth conditions. The PCP stress was administered as a continuous increase in concentration, and samples taken over time were examined for physiological function changes with whole-cell acetate uptake rates (WAURs) and cell viability and for gene expression changes by Affymetrix GeneChip technology and real-time reverse transcriptase PCR. Cell viability, measured by heterotrophic plate counts, showed a moderately steady decrease after exposure to the stressor, but WAURs did not change in response to PCP. In contrast to the physiological data, the microarray data showed significant changes in the expression of several genes. In particular, genes coding for multidrug efflux pumps, including MexAB-OprM, were strongly upregulated. The upregulation of these efflux pumps protected the cells from the potentially toxic effects of PCP, allowing the physiological whole-cell function to remain constant.

* Corresponding author. Mailing address: Environmental and Water Resources Engineering, 418 Durham Hall, Virginia Tech, Blacksburg, VA 24061. Phone: (540) 231-3980. Fax: (540) 231-7916. E-mail: nlove{at}vt.edu

{triangledown} Published ahead of print on 25 May 2007.

{dagger} Present address: Department of Microbiology, University of Washington, Seattle, WA 98105.

Applied and Environmental Microbiology, July 2007, p. 4550-4558, Vol. 73, No. 14
0099-2240/07/$08.00+0     doi:10.1128/AEM.00169-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Wilke, M. S., Heller, M., Creagh, A. L., Haynes, C. A., McIntosh, L. P., Poole, K., Strynadka, N. C. J. (2008). The crystal structure of MexR from Pseudomonas aeruginosa in complex with its antirepressor ArmR. Proc. Natl. Acad. Sci. USA 105: 14832-14837 [Abstract] [Full Text]  


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