Response of Rhodospirillum rubrum S1H to three pharmaceuticals

The present study explores the potential of compound-specific gene-upregulation profiles in the ubiquitous purple nonsulfur bacterium Rhodospirillum rubrum S1H as biomarkers for exposure to surface water contaminants, i.e. high production-volume pharmaceuticals. Even though the pharmaceuticals [i.e., acetylsalicylic acid (ASA), diclofenac (DCF), and 17α-ethinylestradiol (EE2)] did not affect the bacterial growth kinetics at environmentally-relevant concentrations (86nM), whole-genome microarray analyses revealed the upregulation of 128, 49, and 47 genes upon exposure to DCF, ASA, and EE2, respectively. A strong overlap (27-48%) was observed between transcriptional responses, but a total of 93 genes were found to be upregulated in a compound-specific manner. Hence, we were able to identify 74 and 15 potential biomarker genes for DCF and ASA, respectively. DCF specifically induced genes involved mainly in stress response, signal transduction, response regulation, the electron transport chain, and transcription, while ASA specifically induced genes predominantly involved in signal transduction, response regulation, and trans-membrane translocation. Moreover, our findings validated triclosan-specific biomarker genes that were identified previously. As only 4 genes were specifically-upregulated for EE2, no representative biomarker profile was identified. This study illustrates that a pollutant-specific molecular response can be generated in R. rubrum S1H, which could become a relevant model-microorganism to screen for the ecological impact of surface water contaminants in situ. KEYWORDS: environmental impact studies, risk assessment, biosensor, wastewater, micropollutant, aspirin Two-condition experiments. Comparing samples after induction of three pharmaceuticals each with a non-induced samples. Biological triplicate. Each array contains 3 technical replicates.