Resistance to Cr (VI) in Streptomyces R22 isolated from the Salí River

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

Tafí del Valle, Tucumán

Jornada; XIX Jornadas de la Sociedad de Biología de Tucumán.; 2002

Sociedad de Biología de Tucumán

The natural chromium concentration in the environment is low, being generally in its trivalent state (Cr3+), however, due to the anthropogenic pollution, the chromium appears in its hexavalent state (Cr6+). Chromate (Cr6+) compounds are extremely toxic, mutagenic and carcinogenic. There are microorganisms which grow with high Cr6+ concentrations. Studies of chromate resistance have generally focused on Gram negative bacteria. Actinomycetes is a Gram-positive bacteria group with high potential in heavy-metal bioremediation processes. Streptomyces R22 strain, isolated from heavy-metal contaminated sediments of Salí River, was selected due to its tolerance to the ion chromate. We study the capacity of Streptomyces R22 to grow with high Cr6+ concentrations, evaluating the disappearance of Cr6+ in the culture medium. Streptomyces R22 was in Minimal Medium (MM), with 100, 150 and 200 mg l-1 of Cr6+. The biomass was estimated by dry weigh. The Cr6+ concentration was determined colorimetrically by reaction with diphenylcarbazide. Streptomyces R22 showed similar growth in the studied Cr6+ concentrations, producing a reduction of the initial concentration of 11 to 16% and 48 to 56% at 8 and 20 days of incubation respectively. The profile of diminution of  Cr6+ in culture medium depended of the incubation time but not of the initial concentration of Cr6+, showing Streptomyces R22 a high capacity to reduce Cr6+ even at elevated initial concentration. These results confirm the potential utility of Streptomyces R22 in bioremediation processes.