Biofilm Bacterial Community Structure in Streams Affected by Acid Mine Drainage

Abstract

We examined the bacterial communities of epilithic biofilms in 17 streams which represented a gradient ranging from relatively pristine streams to streams highly impacted by acid mine drainage (AMD). A combination of automated ribosomal intergenic spacer analysis with multivariate analysis and ordination provided a sensitive, high-throughput method to monitor the impact of AMD on stream bacterial communities. Significant differences in community structure were detected among neutral to alkaline (pH 6.7 to 8.3), acidic (pH 3.9 to 5.7), and very acidic (pH 2.8 to 3.5) streams. DNA sequence analysis revealed that the acidic streams were generally dominated by bacteria related to the iron-oxidizing genus Gallionella, while the organisms in very acidic streams were less diverse and included a high proportion of acidophilic eukaryotes, including taxa related to the algal genera Navicula and Klebsormidium. Despite the presence of high concentrations of dissolved metals (e.g., Al and Zn) and deposits of iron hydroxide in some of the streams studied, pH was the most important determinant of the observed differences in bacterial community variability. These findings confirm that any restoration activities in such systems must focus on dealing with pH as the first priority.

Geochemical Niches of Iron-Oxidizing Acidophiles in Acidic Coal Mine Drainage

“…pH also controls the aqueous speciation of Fe-SO 4 complexes that impact ferrihydrite or schwertmannite precipitation, which can impair cellular transport processes and impact the availability of Fe 2ϩ to microbial cells (52). Multiple studies have noted the role of pH in partially explaining microbial community distribution in AMD (13)(14)(15). Interestingly, in a study of pilot scale iron oxidation bioreactors, a shift from Ferrovum-to Gallionella-dominated communities occurred with a slight increase in pH (to just above 3) and a slight decrease in Fe 3ϩ during the late stages of operation of one reactor (46).…”

“…For example, a recent analysis of 59 AMD sites in China found that pH was the most important explanatory variable across all sites (15). However, many taxa co-occur in similar pH ranges, and other studies have found that environmental factors, including dissolved oxygen, conductivity, temperature, and iron and other metal concentrations are also important controls on microbial community composition (14)(15)(16)(17)(18)(19)(20). In addition to contemporary environmental selection, microbial populations may also be affected by geographic isolation, which can maintain microbial communities independent of contemporary environmental factors by preserving the influence of past environmental factors or the history of stochastic microbial colonization (19,21).…”

Candidate phylum TM6 genome recovered from a hospital sink biofilm provides genomic insights into this uncultivated phylum

“…S7), which suggests that this phylum has a cosmopolitan distribution, although typically found at low relative abundance. Its ecological distribution (derived from published and unpublished studies that have deposited related sequences in GenBank) includes domestic water sources (17,39,45), acidic cave biofilms, acid mine drainage biofilms (46), wastewater biofilms (47), soil, contaminated groundwater and subsurface sites (48,49), aquatic moss, hypersaline mats, peat bogs, and peat swamps (30,50). These and additional environments where TM6 was detected in 16S rRNA gene clone libraries, including a number of biofilm-related samples, are highlighted in SI Appendix, Table S1.…”

Characterization of Extracellular Polymeric Substances from Acidophilic Microbial Biofilms

“…Biofilms are often considered problematic from the human perspective owing to the damage associated with their presence (rusting, dental plaque formation, and the disease cystic fibrosis) (8). The focus of the present study is on microbial biofilms that are instrumental in the generation of acid mine drainage (AMD) (1,10,16,20,32). The deleterious environmental effects of AMD necessitate research to characterize biofilm structure in such systems, which could provide insight into treatment approaches and environmental control.…”