Selenium and mercury assimilation and detoxification in Pseudomonas fluorescens

This thesis presents a study on the assimilation and detoxification of selenium and mercury and on the interaction between these two elements in Pseudomonas fluorescens. In this thesis, the selenium and mercury detoxification by P. fluorescens through the mechanism of converting selenite and inorganic mercury to elemental forms has been studied, the selenium contents in different cultural fractions were determined and several extracting methods were tested.; The studied bacteria resisted the toxic effect of mercury by converting Hg2+ to Hg0, a less toxic form of Hg. Mercury is toxic because it binds to and inactivates essential thiols that are part of enzymes and proteins. The cell growth profile in mercury media was studied and it was found that mercury was much more toxic than selenium in inhibiting cell growth.; More importantly, the interaction between mercury and selenium has also been studied. Selenium could significantly reduce the accumulation of mercury in P. fluorescens. Probably the most effective protective agent against hazards of mercury poisoning is selenium. It is interesting to notice that mercury can also behave as a protecting agent against selenium intoxication because the bioaccumulation of Se was also prevented by mercury. (Abstract shortened by UMI.)...