title: Detoxification of selenite and mercury by reduction and mutual protection in the assimilation of both elements by Pseudomonas fluorescens.
abstract: A study on the assimilation and detoxification of selenium and mercury and on the interaction between these two elements was conducted on Pseudomonas fluorescens. P. fluorescens was able to convert separately both elements to their elemental forms, which are less toxic and biologically less available. To study the converting mechanism of selenite to elemental Se, cells were grown in the presence of various selenite concentrations and several parameters such as extracellular protein concentrations, pH, carbohydrate concentrations, isocitrate dehydrogenase (ICDH) and malic enzyme were monitored. Transmission electron microscopy (TEM) and various analytical methods were applied to confirm the interaction between selenium and cell. The former appeared as a red precipitate localized predominantly in the consumed culture medium. P. fluorescens also resisted to the toxic effect of mercury by converting Hg2+ to the volatile and less toxic form Hg0. Mercury reductase was likely responsible for the conversion of Hg2+ to Hg0. More importantly, the interaction between mercury and selenium was also studied. The presence of selenite significantly reduced the accumulation of mercury in P. fluorescens. It was also interesting to note that mercury appeared to behave as a protecting agent against selenium intoxication as the bioaccumulation of Se was also inhibited by this metal. The formation of Se-Hg complexes could explain this mutual protective effect. No precipitate of elemental Se could be detected when Hg was present in the cultures.
authors.affiliation: Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada, P3E 2C6. nbelzile@laurentian.ca
authors.forename: Nelson
authors.initials: N
authors.lastname: Belzile
authors.forename: Gao Jun
authors.initials: GJ
authors.lastname: Wu
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Chen
authors.forename: Vasu D
authors.initials: VD
authors.lastname: Appanna
mesh_terms: D001673:Biodegradation, Environmental; D002241:Carbohydrates / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D008628:Mercury / Q000378:metabolism* / Q000633:toxicity; D046529:Microscopy, Electron, Transmission; D011551:Pseudomonas fluorescens / Q000378:metabolism* / Q000648:ultrastructure; D018038:Sodium Selenite / Q000378:metabolism* / Q000633:toxicity; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000378:metabolism* / Q000633:toxicity
chemical_list: D002241:Carbohydrates; D014874:Water Pollutants, Chemical; D008291:Malate Dehydrogenase; D007521:Isocitrate Dehydrogenase; D008628:Mercury; D018038:Sodium Selenite