Evolution of microbial "streamer" growths in an acidic, metal-contaminated stream draining an abandoned underground copper mine.

A nine year study was carried out on the evolution of macroscopic "acid streamer" growths in acidic, metal-rich mine water from the point of construction of a new channel to drain an abandoned underground copper mine. The new channel became rapidly colonized by acidophilic bacteria: two species of autotrophic iron-oxidizers (Acidithiobacillus ferrivorans and "Ferrovum myxofaciens") and a heterotrophic iron-oxidizer (a novel genus/species with the proposed name "Acidithrix ferrooxidans"). The same bacteria dominated the acid streamer communities for the entire nine year period, with the autotrophic species accounting for ~80% of the micro-organisms in the streamer growths (as determined by terminal restriction enzyme fragment length polymorphism (T-RFLP) analysis).

Evidence that the potential for dissimilatory ferric iron reduction is widespread among acidophilic heterotrophic bacteria.

Nineteen characterized strains and isolates of acidophilic heterotrophic bacteria were screened for their abilities to catalyse the reductive dissolution of the ferric iron mineral schwertmannite, under oxygen-limiting conditions. Acidocella facilis, Acidobacterium capsulatum, and all of the Acidiphilium, Acidocella and Acidobacterium-like isolates that grew in liquid cultures were able to reduce iron. In contrast, neither Acidisphaera rubrifaciens nor three Acidisphaera-like isolates tested were found to have the capacity for dissimilatory iron reduction.

Macroscopic streamer growths in acidic, metal-rich mine waters in north wales consist of novel and remarkably simple bacterial communities.

The microbial composition of acid streamers (macroscopic biofilms) in acidic, metal-rich waters in two locations (an abandoned copper mine and a chalybeate spa) in north Wales was studied using cultivation-based and biomolecular techniques. Known chemolithotrophic and heterotrophic acidophiles were readily isolated from disrupted streamers, but they accounted for only <1 to 7% of the total microorganisms present. Fluorescent in situ hybridization (FISH) revealed that 80 to 90% of the microbes in both types of streamers were beta-Proteobacteria.

Oxidation of arsenite by Thiomonas strains and characterization of Thiomonas arsenivorans sp. nov.

A novel bacterium, strain b6(T) (T=type strain), was isolated from a disused mine site by growth using arsenite [As(III)] as energy source in a simple mineral medium. Cells of strain b6(T) were rod-shaped, Gram-negative, non-sporulating and motile. Optimum growth occurred at temperatures between 20 and 30 degrees C, and at pH between 4.