The work presented investigates various aspects of glutathione-dependent electrophile metabolism in bacteria. First, we studied the response of <I>Staphyloccocus aureus</I> to the electrophile methylglyoxal. We found that under our experimental conditions, this organism is incapable of methylglyoxal metabolism by either glutatione-dependent or independent mechanisms. Glutatione was found to sensitise <I>S. aureus</I> to methylglyoxal. Furthermore, the sulphydryl group of glutathione is essential in this process. This implies that a glutathione conjugate may be involved in the increased sensitivity. Methylglyoxal does not activate K<sup>+</sup> efflux from <I>S. aureus</I> cells, suggesting that the KefB K<sup>+</sup> efflux system is absent from this organism. NEM activates a slow release of K<sup>+</sup> indicating that the KefC system may be present. We investigated the response of <I>E. coli</I> and <I>Pseudomonas</I> sp. to the electrophilic herbicide alachlor. This compound activates a release of K<sup>+</sup> from <I>E.coli</I> but not from any Pseudomona tested. K<sup>+</sup> efflux is not mediated by KefB, KefC or the major mechanosensitive channels. In addition to the K<sup>+</sup> efflux, alachlor stimulated an increase in the absorbance at 265 nm of media containing <I>E. coli</I>. It is not fully understood what this absorbance increase represents but it may reflect an increase in the solubility of alachlor over time. Despite its potential toxicity, alachlor did not affect the growth of either <I>E. coli</I> or <I>P. fragi</I>. However, when <I>E. coli</I> were treated with EDTA they became sensitive to alachlor. This result and data obtained using <sup>14</sup>C-labelled alachlor indicated that alachlor does not normally enter <I>E. coli</I> cells. Finally, we investigated the response of <I>E. coli</I> expressing <I>dcm</I>A from <I>Methylophilus</I> sp. DM11 to DCM. Addition of DCM resulted in immediate cessation of growth, which was not due to formaldehyde accumulation. Cells washed free of DCM after a short incubation resume growth at the pre-addition rate, indicating DCM dehalogenation causes no permanent damage to the cell.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:312361 |
| Date | January 2000 |
| Creators | Evans, Gareth J. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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