Reponse of Shewanella oneidensis MR-1 to long-term stress with ionic liquid: comparative studies on MR-1 and SH-1, an acclimated strain

초록

Ionic liquids(ILs) have been known as a green solvent because they are stable solvents. However, it is not clearly known if ILs may possess potential toxic activities when released into the environment. In this study, we investigated the effects of long-term exposure to various ILs on Shewanella oneidensis MR-1, an environmental bacterium. MR-1 was acclimated through repeated exposure to ILs at sublethal concentrations, which were gradually increased to acclimate MR-1. Among the resulting acclimated strains we selected an [Omim][BF4] acclimated strain for further study. The latter strain was named as SH-1 and compared with MR-1 in various aspects including morphology, growth , and cell surface hydrophobicity (CSH). When grown in a complex medium without IL SH-1 showed slower growth compared to the MR-1. In the presence of IL growth of SH-1 was slower than that of SH-1 grown without IL. Cell morphology was observed by scanning electron microscopy(SEM) for each strains. Compared to the MR-1, SH-1 showed significantly elongated cell shape. Fourier Transform Infrared (FT-IR) spectrometer analysis was done for both MR-1 and SH-1 to reveal possible differences in cellular composition. There was no significant difference between two strains. Cell surface hydrophobicity(CSH) analysis was conducted because no significant difference was detected at FT-IR analysis. In the absence of ILs there was no significant difference between the two strains. However, upon exposure to ILs at sublethal concentrations, CSH of SH-1 was rapidly increased while that of MR-1 was not affected.