Submitted to: In Situ and on Site Bioremediation Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 10, 2006
Publication Date: May 7, 2007
Citation: Hunter, W.J., Kuykendall, L.D. 2007. Removal of selenite from groundwater by rhizobium sp. strain b1. In Situ and on Site Bioremediation Symposium Proceedings. Abstract. Technical Abstract: Selenite is highly soluble, mobile and potentially toxic to humans and animals. In contrast, insoluble Se0 is not available for biological uptake and is generally non-toxic. Because of these contrasting properties, in-situ biological precipitation has been proposed as a remediation method to remove selenite from contaminated groundwaters. This study describes a bacterial strain that was isolated from a laboratory biobarrier used for the reduction of selenate. The strain, referred to as strain B1, reduces selenite to elemental red selenium. Biochemical, morphological, and 16S rDNA sequence alignment show that strain B1 can be classified as a Rhizobium sp. related to R. radiobacter or R. rubi. Strain B1 reduces selenite to elemental selenium under both aerobic and denitrifying conditions but does not reduce selenate. In batch studies, selenite was removed from the growth medium at a rate as high as 2 µMoles / mg cell protein / day. Selenite reduction resulted in the formation of selenium nanospheres that were 0.27 ± 0.01(mean ± SEM) µm in diameter. Native gel electrophoresis showed two activities associated with the reduction of selenite by strain B1. One activity has a molecular weight of ~ 110 kD and the other a molecular weight ~ 39 kD. A nitrite reductase with a molecular weight of ~ 110 kD was also identified suggesting that this protein may be one of the two activities that play a role in the reduction of selenite. Rhizobium sp. B1 has shown the potential to remediate ground and surface waters that are contaminated with selenite.