CHROMIUM BIOACCUMULATION BY STREPTOMYCES sp. MC1

POLTI, MARTA ALEJANDRA; CRISTÓBAL, HÉCTOR; AMOROSO, MARÍA JULIA; ABATE; CARLOS MAURICIO

Newcastle, Reino Unido

Simposio; ISBA; 2007

Sociedad Intenacional de Actinomycetes

In natural water and subsurface soils, chromium occurs in two major oxidation states III and VI1. Chromium (VI) is the major chromium species used in industry and hence is the common pollutant in soil and waste water, while Cr(III) is a relatively insoluble and non-toxic. Cr(VI) produce toxicity acute and chronic, neurotoxicity, dermatotoxicity, genotoxicity, carcinogenicity and immunotoxicity. Cr(VI) compounds are 1,000 fold more toxics than Cr(III) compounds2, biological transformation of Cr (VI) to Cr (III) by enzymatic reduction is a means of decontamination. This biological reduction may provide a less costly and environmentally friendly approach to remediation3. A chromium (VI) resistant actinomycete strain, Streptomyces sp. MC1, previously isolated in our lab4, has the ability of reducing Cr(VI) 60 % after 4.5 days of growth5,6, and accumulating it as Cr(III)7. The aim of this work is to reveal the chromium accumulation capacity by this strain and elucidate the differential protein expression of Streptomyces sp. MC1 when it’s exposed to Cr(VI) stress. Streptomyces MC1 was grew in minimal medium with Cr(VI) 1 mM, and without this metal. The harvested cells were used for cytochemical staining associated to transmission electron microscopy and a sample was disrupted, by press French and used to perform electrophoresis. Using the Timm´s reagent8, Cr(III) deposits appeared as black grains of reduced silver within the cell exposed; whereas cells cultivated in a chromium-free medium did not show clear deposits. Cr(VI) exposed cells protein profile analyzed by PAGE and 2D-PAGE showed differential expression patterns of several proteins compared to the control. Further studies are necessaries to determine if those proteins are involved in Cr(VI) resistance.