S178: Bacterial arsenic transformations in the rhizosphere of the arsenic hyperaccumulator fern Pteris vittata

The arsenic hyperaccumulator fern Pteris vittata provides a unique environment for microbes that play important roles in arsenic transformation and cycling in the environment.  Because of their potential utilities in improving arsenic phytoremediation of the fern, we have characterized arsenic resistant bacteria from the rhizosphere of the fern.  Seven isolates of arsenate-reducing bacteria from the rhizosphere were species of the Pseudomonas, that were UV positive and significantly improved solubilization of arsenic from insoluble forms of arsenic minerals.  We identified four arsenite oxidizing bacteria from the hydroponic system where P. vittata was grown.  These isolates differed from each other in their arsenic tolerance and arsenic transformation abilities.  One isolate C-1, closest to Commamonas testosterone. had abilities to do both arsenate reduction and arsenite oxidation.   Our results indicate the potential to manipulate microbial-mediated arsenic transformations in the fern rhizosphere to improve phytoremediation of arsenic-contaminated environments.