A natural rice rhizospheric bacterium abates arsenic accumulation in rice (Oryza sativa L.)
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A natural rice rhizospheric isolate abates arsenic uptake in rice by increasing Fe plaque formation on rice roots.
Rice (Oryza sativa L.) is the staple food for over half of the world’s population, but its quality and yield are impacted by arsenic (As) in some regions of the world. Bacterial inoculants may be able to mitigate the negative impacts of arsenic assimilation in rice, and we identified a nonpathogenic, naturally occurring rice rhizospheric bacterium that decreases As accumulation in rice shoots in laboratory experiments. We isolated several proteobacterial strains from a rice rhizosphere that promote rice growth and enhance the oxidizing environment surrounding rice root. One Pantoea sp. strain (EA106) also demonstrated increased iron (Fe)-siderophore in culture. We evaluated EA106’s ability to impact rice growth in the presence of arsenic, by inoculation of plants with EA106 (or control), subsequently grew the plants in As-supplemented medium, and quantified the resulting plant biomass, Fe and As concentrations, localization of Fe and As, and Fe plaque formation in EA106-treated and control plants. These results show that both arsenic and iron concentrations in rice can be altered by inoculation with the soil microbe EA106. The enhanced accumulation of Fe in the roots and in root plaques suggests that EA106 inoculation improves Fe uptake by the root and promotes the formation of a more oxidative environment in the rhizosphere, thereby allowing more expansive plaque formation. Therefore, this microbe may have the potential to increase food quality through a reduction in accumulation of toxic As species within the aerial portions of the plant.
KeywordsArsenate Arsenite Fe plaque Pantoea Rhizosphere Rhizobacteria
We thank Samuel M. Webb (beam line 10–2 and 2–3 for assistance with XRF imaging and µXRD analyses. The authors also thank Dr. Jeffrey L. Caplan and the faculty Deborah Powell and Rebekah R. Helton, Bio-imaging center, Delaware Biotechnology Institute for their help with microscopic studies. H. P. B. acknowledges the support from NSF Award 0923806. H. P. B and D. L. S. acknowledge the support from DE-EPSCoR program, and A. L. S. acknowledges support from NSF Award 1338389. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.
We have followed all the guidelines of the Committee on Publication Ethics (COPE).
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