123-50 Arsenic Transformation In Soils by Arsenic-Resistant Bacteria Isolated From the Rhizosphere of Hyperaccumulator Pteris Vittata L.



Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

Piyasa Ghosh, University of Florida, Gainesville, FL, Bala Rathinasabapathi, Horticultural Sciences Department, University of Florida, Gainesville, FL and Lena Ma, Soil and Water science, Unversity of Florida, Gainesville, FL
Arsenic hyperaccumulator Pteris vittata L (Chinese Brake fern) may accumulate up to 2.3% As in its biomass, making it a viable candidate for phytoremediation of arsenic contaminated sites. Rhizosphere soils from naturally growing P. vittata and bulk soils from 10 feet away were collected from four sites in Florida: Archer Feed Store (AF), Archer Ministorage (AM), Rainbow Springs (RS) and Crystal Quarry site (CQ). When incubated in nutrient medium containing 1 mM of arsenate (AsV), >80% of the AsV in the soils was reduced to arsenite (AsIII). When incubated in nutrient medium containing 1 mM AsIII, significantly more AsIII oxidation occurred in the bulk soils than rhizosphere soils while AsV reduction was equally high in both soils. To test the role of rhizosphere bacteria in arsenic transformation in soils, we isolated and characterized seven arsenic-resistant bacteria at 10 mM AsV, which were all fluorescent indicating the presence of siderophores. We tested the individual rates of AsIII oxidation and AsVreduction in modified Luria Bertani medium containing 1 mM AsV or AsIII. All bacteria were capable of both AsIII oxidation and AsV reduction though their rates were different.  Our results showed that rhizosphere bacteria are important in arsenic transformation in soils.

Keywords: arsenic-resistant bacteria, fluorescence, rhizosphere, hyperaccumulator, Chinese brake fern.

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Microbe, Plant , and Soil Interactions (Includes Graduate Student Poster Competition)