Macroscopic Streamer Growths in Acidic, Metal-Rich Mine Waters in North Wales Consist of Novel and Remarkably Simple Bacterial Communities

Abstract

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 cultivationbased 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 ␤-Proteobacteria. Terminal restriction fragment length polymorphism analysis of the streamers suggested that a single bacterial species was dominant in the copper mine streamers, while two distinct bacteria (one of which was identical to the bacterium found in the copper mine streamers) accounted for about 90% of the streamers in the spa water. 16S rRNA gene clone libraries showed that the ␤-proteobacterium found in both locations was closely related to a clone detected previously in acid mine drainage in California and that its closest characterized relatives were neutrophilic ammonium oxidizers. Using a modified isolation technique, this bacterium was isolated from the copper mine streamers and shown to be a novel acidophilic autotrophic iron oxidizer. The ␤-proteobacterium found only in the spa streamers was closely related to the neutrophilic iron oxidizer Gallionella ferruginea. FISH analysis using oligonucleotide probes that targeted the two ␤-proteobacteria confirmed that the biodiversity of the streamers in both locations was very limited. The microbial compositions of the acid streamers found at the two north Wales sites are very different from the microbial compositions of the previously described acid streamers found at Iron Mountain, California, and the Rio Tinto, Spain.Microorganisms that inhabit the most extreme acidic niches on our planet (acidophiles) are highly diverse in terms of their physiologies and phylogenetic relationships (4, 18). There have been many reports of macroscopic microbial growth in extremely acidic (pH Ͻ3) metal-rich environments (mostly associated with mines and mine drainage waters) following the initial description by Lackey (26). These growths may occur as gelatinous filaments in flowing mine waters (acid streamers), as stalactite-like forms hanging from pit props and underground roofs (microbial pipes and snotites), or as thick biofilms. One of the first attempts to isolate bacteria from acid streamers was the attempt of Dugan et al. (11), although all of the isolates obtained in that study were neutrophilic rather than acidophilic. In contrast, acidophilic chemolithotrophic and heterotrophic acidophilic bacteria were isolated by McGinness and Johnson from acid streamers found in an abandoned pyrite mine (Cae Coch) in north Wales (32). These researchers considered acid streamers to be mixed communities of iron-and sulfur-oxidizing acidophiles, which acted as the primary producers in the mine, and heterotrophic bacteria, which utilized lysates and exuda...

Characterization of Fe(II) oxidizing bacterial activities and communities at two acidic Appalachian coalmine drainage-impacted sites

“…Similar RISA banding patterns of the GB and FR sources and Fe(III)-rich sediments suggested similarly simple community structures among these sampling locations. These observations are consistent with previous work suggesting that due to the relatively harsh chemical conditions of AMD, the diversity of microorganisms present in AMD systems is generally lower than that of less chemically 'extreme' systems (for example, soils or sediments of circumneutral pH) (Baker and Banfield, 2003;Hallberg et al, 2006). Therefore, it appears that the regular input of unaltered AMD is the primary controlling factor on the structure of microbial communities in AMD-impacted systems.…”

“…Hallberg and Johnson (2003) point out that the pH of the of AMD-impacted systems may influence the composition of Fe(II)OB communities, with relatively low pH (o3.0) favoring the growth and activity of A. ferrooxidans and L. ferrooxidans, and relatively high pH (43.0) favoring the growth and activity of 'moderately acidophilic' Fe(II)OB that are phyolgenetically related to organisms that we detected in the GB and FR systems. Although the Actinobacteria and Gammaproteobacteria (including A. ferrooxidans) that we have detected in the GB and FR systems are closely related to known acidophilic Fe(II)OB (Johnson and Roberto, 1997;Hallberg and Johnson, 2003;Johnson et al, 2003;Druschel et al, 2004;Hallberg and Johnson, 2005;Hallberg et al, 2006), we definitively cannot assign Fe(II) oxidizing activity in the GB and FR systems to these organisms. However, this work does suggest that oxidative precipitation of Fe(II) may be mediated by diverse groups of organisms, several of which have only recently been identified as Fe(II)OB and are poorly characterized.…”

“…However, this work does suggest that oxidative precipitation of Fe(II) may be mediated by diverse groups of organisms, several of which have only recently been identified as Fe(II)OB and are poorly characterized. We also point out that we have not assessed the role of archaea in the GB and FR systems, though previous studies have suggested that bacteria predominantly mediate Fe(II) oxidation in moderately acidic systems (Baker and Banfield, 2003;Hallberg et al, 2006;Nicormat et al, 2006b).…”

“…Actinobacterial phylotypes recovered from the FR system (and one from the GB system) were members of the Acidimicrobiales subclass (Figure 4). The Acidimicrobiales consist of several acidophilic Fe(II)OB, including the heterotrophic Fe(II)OB Ferrimicrobium acidiphilum (Lane et al, 1992;Clark and Norris, 1996;Johnson and Roberto, 1997;Johnson et al, 2003;Druschel et al, 2004;Hallberg and Johnson, 2005;Hallberg et al, 2006). Gammaproteobacterial phylotypes recovered from the FR system were members of the orders Chromatiales, Legionellales and Xanthomonadales ( Figure 5).…”

Architectural differentiation reflects bacterial community structure in stream biofilms

“…Such streamers also form frequently in benthic stream biofilms (Figures 1a and b). They can associate with diatoms ( Figure 1c) and other algae to develop extraordinarily long filaments in circumneutral streams (Besemer et al, 2007) and contribute most biomass to acidophilic species-poor biofilms (Hallberg et al, 2006).…”