title: Transcriptome analysis reveals that multidrug efflux genes are upregulated to protect Pseudomonas aeruginosa from pentachlorophenol stress.
abstract: 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.
authors.affiliation: Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
authors.forename: Jocelyn Fraga
authors.initials: JF
authors.lastname: Muller
authors.forename: Ann M
authors.initials: AM
authors.lastname: Stevens
authors.forename: Johanna
authors.initials: J
authors.lastname: Craig
authors.forename: Nancy G
authors.initials: NG
authors.lastname: Love
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics; D015536:Down-Regulation; D024881:Drug Resistance, Bacterial; D004785:Environmental Pollutants / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D050296:Microbial Viability; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D010416:Pentachlorophenol / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism*; D012329:RNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012808:Sigma Factor / Q000235:genetics; D015854:Up-Regulation
chemical_list: D019342:Acetic Acid; D001426:Bacterial Proteins; D004785:Environmental Pollutants; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010416:Pentachlorophenol; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria