Metal tolerance of yeasts isolated from extremely acidic aquatic environments in Portugal and Argentina

GADANHO, M., ALMEIDA, P., RUSSO, G., LIBKIND, D., VAN BROOCK, MR(GIRAUDO MARÍA ROSA) & TENREIRO, R

Faro, Portugal

Simposio; 10th Symposium in Aquatic Microbial Ecology; 2007

Eighteen yeasts isolated from two distinct acidic aquatic environments (ranging from pH 1.7 to 2.8) were studied. Fourteen strains were obtained from acid mine drainage (AMD) collected at the Iberian Pyrite Belt (São Domingos, Portugal) and four strains were obtained from Agrio River (Copahue Volcano, Patagonia, Argentina). The four Argentinean strains belong to different species also found in the Portuguese AMD samples. All the strains were characterized for tolerance to eight metal sulfates. The maximum concentration tolerated (MCT) by each strain was determined in liquid medium using an automated plate reader (Bioscreen C) and log2 metal dilutions. Besides the high magnesium tolerance recorded for several of the strains tested (>1.862M), the values obtained ranged from <0.5mM for nickel to >811mM for lithium. For the remaining metals the MCTs were: copper (390.0mM), nickel (>17.1mM), cobalt (>14.4mM), zinc (>99.0mM), cadmium (>27.9mM) and manganese (>409.5mM). Principal component analysis (PCA) of growth data revealed positive associations between zinc and copper and between magnesium and cadmium effects. On the other hand, negative associations were observed between nickel and manganese and between the pair zinc/copper and the pair magnesium/cadmium. Additionally, PCA brought together strains belonging to the same species regardless their origin (Portugal or Argentina), suggesting metal tolerance as a species specific trait for these yeasts. This combined spatial analysis of metals and strains enabled the definition and ranking of metal multitolerant strains and provides important new data of ecological and applied significance.