Soil chromium bioremediation: Synergic activity of actinobacteria and plants

The aim of this work was to evaluate a strategy to reduce the bioavailable chromium fraction in soil, using a Cr(VI) resistant microorganism, Streptomyces sp. MC1, under non sterile conditions, with maize plants as bioindicator and/or bioremediator. Soil samples were contaminated with 100, 200 and 400 mg kg(-1) of Cr(VI) or Cr(III). Bioavailable chromium (35%) was only detected in samples with Cr(VI). Soil samples with Cr(VI) 200 mg kg(-1) were inoculated with Streptomyces sp. MC1, and bioavailable chromium decreased up to 73%. Zea mays seedlings were planted in soil samples contaminated with chromium. Plantlets accumulated chromium mainly as Cr(III), and biomass decreased up to 88%. Streptomyces sp. MC1 was inoculated in soil samples contaminated with 200 mg kg(-1) of Cr(VI) and Z. mays seedlings were planted. Streptomyces sp. MC1 caused Z mays biomass increase (57%), chromium accumulation and bioavailable chromium decreased up to 46% and 96%, respectively. This work constitutes the first contribution of cooperative action between actinobacteria and Z. mays in the bioremediation of Cr(VI) contaminated soil. The large removal capacity of bioavailable chromium by Streptomyces sp. MC1 and Z. mays infers that they could be successfully applied together in bioremediation of soils contaminated with Cr(VI). (C) 2011 Elsevier Ltd. All rights reserved.