Methylmercury inhibits growth and induces membrane changes in Pseudomonas putida

Abstract

1 univ. of Ljubljana, Biotechnical Fac., dept. of Animal Science, groblje 3, SI-1230 domžale, Slovenia, e-mail: masa.vodovnik@bf.uni-lj.si 2 Laboratory for environmental science and engineering, national institute of chemistry, hajdrihova 19, SI-1000 Ljubljana, Slovenia 3 Same address as 1, Ph.d. 4 Same address as 1, Ph.d., e-mail: romana.marinsek@bf.uni-lj.si most toxic metals is certainly mercury, which represents a significant concern especially in aquatic ecosystems at sites with industrial or mining activities. Mining operations in areas rich in cinnabar ore may represent strong sources of hg for many years even after mining has been discontinued (Benoit et al., 1994). One of mercury (hg) affected sites also lies in western part of Slovenia where Methylmercury inhibits growth and induces membrane changes in Pseudomonas putida A bacterial model system (Pseudomonas putida dSM 50026) was used in this research to assess toxicity of the environmentally relevant concentrations of mercury species (Mehg and hg(II)) that represent important pollutants of aquatic ecosystems at sites of industrial or mining activities. In addition to direct monitoring of bacterial growth, we also analyzed fatty acid profiles of exposed and non-exposed cultures to determine possible toxic effects manifested on membrane level. The results showed that exposure of P. putida to hg(II) in concentrations of 0.2–200 μg/L did not have any significant effects on growth nor fatty acid composition of exposed bacterial culture. On the other hand, when bacteria were exposed to up to 1600-times lower concentrations of Mehg (0.12–12.5 μg/L), growth inhibition as well as significant changes in fatty acid composition were detected. Observed adaptive membrane changes due to Mehg exposure were similar to those associated with responses to organic solvents and some other membrane-disrupting compounds.