Genetic and physiological diversity of phylogenetically and geographically distinct groups of Arthrobacter isolated from lead-zinc mine tailings.

The phylogenetic positions of 60 bacterial strains isolated from three tailing piles were determined by analyzing their partial 16S rRNA gene sequences. These strains were divided into three phylogenetically distinct groups of Arthrobacter and likely represented several non-described species. The physiological diversities of these phylogenetically and geographically distinct populations were evaluated based on their resistance to five heavy metals (Zn, Pb, Cd, Cu and Co) and four antibiotics (Kan, Rif, Str and Amp), and differences in utilization of 49 carbon sources. Genetic differentiations were demonstrated with randomly amplified polymorphic DNA (RAPD) analysis. These biological parameters were significantly different among three phylogenetically distinct groups. Notably, detectable differences were also observed among three geographically distinct subdivisions with similar taxonomic position. These results indicate that mine tailings are an ideal site for investigating the differentiation of natural bacterial populations in response to extreme metal contamination. Additionally, these environments appear to harbor many previously not characterized bacterial species, which are potentially important candidates for application in bioremediation due to their remarkable resistance to multiple metals.