Bacterial communities associated with a mineral weathering profile at a sulphidic mine tailings dump in arid Western Australia.

We investigated bacterial community assemblages and functions down a hill slope contaminated by tailings from a volcanogenic massive sulphide mine in arid Western Australia. Weathering of waste rock, high in S and Fe, had resulted in a varying elemental dispersal down a face of the tailings hill. Bacterial community assemblage, characterised by PCR-DGGE fingerprinting, was significantly associated with electrical conductivity (E.C.) (ρ = 0.664; P < 0.01). Analysis of mobile salts showed that E.C. values were driven by ionic S, Zn, Cl and Al. The bacterial community assemblage was directly characterised across an E.C. gradient using an oligonucleotide microarray (PhyloChip). The dominant taxa at the site were Proteobacteria, Actinobacteria and Firmicutes; however, 37 phyla were detected. The most responsive taxa to variation in E.C. was Acidobacteria (negative correlation). Patterns of heterotrophic processes (BioLog analysis) were also best explained by variation in E.C. (ρ = 0.53; P < 0.01), showing a link between primary mineral weathering by lithotrophic bacteria and abiotic processes, and secondary biogeochemical processes by heterotrophic taxa. These data significantly broaden our knowledge of the bacteria present in metallomorphic ecosystems, establish that mobile phase elements are key drivers of community structure, and that primary biogeochemical cycling is directly influencing other geochemical interactions in the samples.