Open AccessToxicogenomic Response of Rhodospirillum rubrum S1H to the Micropollutant Triclosan
Author(s) -
Benny F. G. Pycke,
Guido Vanermen,
Pieter Monsieurs,
Heleen De Wever,
Max Mergeay,
Willy Verstraete,
Natalie Leys
Publication year - 2010
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.01254-09
Subject(s) - triclosan , microbiology and biotechnology , rhodospirillum rubrum , environmental chemistry , biology , microorganism , biofilm , food science , chemistry , bacteria , genetics , medicine , pathology
In the framework of the Micro-Ecological Life Support System Alternative (MELiSSA) project, a pilot study was performed to identify the effects of triclosan on the MELiSSA carbon-mineralizing microorganismRhodospirillum rubrum S1H. Triclosan is a biocide that is commonly found in human excrement and is considered an emerging pollutant in wastewater and the environment. Chronic exposure to MELiSSA-relevant concentrations (≥25 μg liter−1 ) of triclosan resulted in a significant extension of the lag phase of this organism but hardly affected the growth rate. Analytical determinations gave no indication of triclosan biodegradation during the growth experiment, and flow cytometric viability analyses revealed that triclosan is bacteriostatic and only slightly toxic toR. rubrum S1H. Using microarray analyses, the genetic mechanisms supporting the reversibility of triclosan-induced inhibition were scrutinized. An extremely triclosan-responsive cluster of four small adjacent genes was identified, for which there was up to 34-fold induction with 25 μg liter−1 triclosan. These four genes, for which the designationmuf (micropollutant-upregulated factor) is proposed, appear to be unique toR. rubrum and are shown here for the first time to be involved in the response to stress. Moreover, numerous other systems that are associated with the proton motive force were shown to be responsive to triclosan, but they were never as highly upregulated as themuf genes. In response to triclosan,R. rubrum S1H induced transcription of the phage shock protein operon (pspABC ), numerous efflux systems, cell envelope consolidation mechanisms, the oxidative stress response, beta-oxidation, and carbonic anhydrase, while there was downregulation of bacterial conjugation and carboxysome synthesis genes. Themuf genes and three efflux-related genes showed the most potential to be low-dose biomarkers.