Reduction of selenite to elemental Selenium by Pantoea agglomerans

Abstract

Selenium is required and essential for the growth and metabolism of several biological systems. Its transformation in the environment occurs mainly by the activity of microorganisms, able to reduce selenite into elemental Selenium. Pantoea agglomerans UC-32 reduces selenite to nanoparticles of elemental Selenium. The aims of this work were to determine the kinetics of selenite reduction and to determine the cellular localization of this activity in P. agglomerans UC-32. The selenite reducing activity of P. agglomerans UC-32 was assayed in the presence of different selenite concentrations and the decrease of selenite and appearance of elemental Selenium were evaluated. The location of this activity was studied by cellular fractioning and zymography. Results indicated that the selenite reducing enzyme saturates at low concentrations of this compound and the zymogram localized this activity in the cytoplasmic fraction and showed that NADPH is required as coenzyme. In conclusion, P. agglomerans reduces, under aerobic conditions, selenite into insoluble elemental Selenium, immobilized in the biomass and that the enzyme catalyzing this reduction is cytoplasmatic. These characteristics would allow the "green synthesis" of selenium nanoparticles which have application in the bioremediation of different contaminated matrices, such as soil or water.