Copper resistance in yeasts isolated from copper polluted area of Argentina

L.B. VILLEGAS; M.J AMOROSO; O.I VILLEGAS; L.I.C. DE FIGUEROA

Basel, Switzerland

Congreso; 11th European Congress on Biotechnology.; 2003

Copper, an essential trace metal, is utilized as a cofactor in variety of redox and hydrolytic proteins. However, excess copper is highly toxic to most organisms. Microorganisms (like yeasts) may be used to remediate wastewaters or soils contaminated with cooper. This capacity can be used to concentrate, remove and recover copper from different contaminated sites The aim of this study was to analyze the growth and uptake copper capacity of three isolated yeasts from copper polluted area in Northwest Argentina. Isolates designated as RCL-3, RCL-4 and RCL-11 were obtained from a sediment sample of a Argentina mine containing high copper level. Diazonium Blue B test showed that RCL-3 and RCL-4 (flocculent) belong to ascomycetous and RCL-11 belongs to basidiomycetous taxa. Yeasts were cultured in minimal liquid medium, yeast nitrogen-base (YNB) containing Cu2+ as CuSO4, at 0.5, 1, 3 and 5 mM respectively. As positive control, cultures without this heavy metal were performed. Cultures were incubated at 30 oC, 250 rpm during a week. The growth of RCL-3 and RCL-11 was followed by turbidity at 620 nm, and measured by counting cells number. RCL-4 was measured by dry weight. Total copper concentration in the supernatants of the culture media was determined by atomic absorption spectrophotometer. The three yeasts grew at 0.5 mM copper concentration, as the positive control. RCL-4 showed a lag period of 72, RCL-11 of 24 and RCL-3 of 7 hours. RCL-3 and RCL-11 grew also at 1 mM of cooper, while RCL-4 showed limited growth at this concentration. Only RCL-3 could growth at 3 mM. The colour of this yeast was darker than the control. Concentrations higher than 3 mM inhibited the growth of all the yeasts during one week. The yeast copper resistance is important for understanding how these microorganisms develop mechanisms for surviving in presence of copper.