BACTERIAL REDUCTION OF SELENITE TO ELEMENTAL SELENIUM

It is well known that many microorganisms can reduce the highly toxic soluble selenium oxyanions (selenate and selenite) to a much less toxi c insoluble form, namely elemental selenium. We are developing a bacte rial treatment system to mitigate selenium-contaminated waste streams using Pseudomonas fluorescens and Bacillus subtilis, respectively, as model Gram (-) and (+) soil bacteria. Our studies demonstrate that bot h strains reduce selenite to elemental selenium. The selenite detoxifi cation system is independent of nitrite and sulfite electron accepters , but dependent on the substrate provided for growth. Elemental seleni um is deposited as granules throughout the cell, or between the cell w all and the plasma membrane in P. fluorescens and B. subtilis, respect ively. In B. subtilis, thioredoxin is induced in the presence of selen ite.