Recognition of a Biofilm at the Sediment–water Interface of an Acid Mine Drainage-Contaminated Stream, and Its Role in Controlling Iron Flux

Abstract

Material collected over a month on plates attached to the bed of the Afon Goch, Anglesey, a stream highly contaminated by acid mine drainage (AMD), was either examined intact by electron microscopy or suspended and cultured to reveal the presence of microbiota. Certain of the aerobic microbiota were identi®ed, the genus Pseudomonas formed the commonest isolate and cultures of Serratia plymuthica were grown in order to compare the bio®lms formed with the material collected in the Afon Goch. The material at the sediment±water interface of the Afon Goch was of similar underlying morphology to that of the cultured bio®lms. However, the former had a super®cial granular coating of equidimensional (60±100 nm) and evenly spaced iron rich particles (determined by X-ray microanalysis). The sediment± water interface of this AMD-contaminated stream is therefore best described as a highly contaminated bio®lm. Evidence from previous work suggests that the streambed is active in iron removal from the water column. The intimate association of iron with microbiota at the streambed, therefore, implies that iron¯ux prediction may not be possible from physical and chemical data alone but requires knowledge of bio®lm physiology and ecology.Microbially mediated metal precipitation, both by single bacteria and by bio®lms, has been reported elsewhere but mass balance considerations suggest that this explanation cannot hold good for the large amounts of iron hydroxide depositing from waters of the prevalent pH and redox status. Filtered stream water analyses indicate the presence of colloidal iron hydroxide and also its removal downstream where ochreous (iron hydroxide rich) material accumulates. The process of iron immobilization is likely to be the attraction and physical trapping of colloidal iron hydroxide by extracellular polymeric substances (EPS) which constitute the matrix of bio®lms.

Characterization of an acid rock drainage microbiome and transcriptome at the Ely Copper Mine Superfund site

“…Pseudomonas (2.6–3.3%), Bradyrhizobium (1.7–4.1%), and Streptomyces (2.9–5.0%) were the most abundantly annotated microbial genera in all samples ( Fig 3 ). Although not consistent with our hypothesis, acid-tolerant bacteria from these genera have been isolated from other mines [ 17 , 58 – 64 ], producing nutrients and mediating the flux of metal ions [ 65 , 66 ]. Species of Leptospirillum , Acidithiobacillus , Acidiphilium , and Thiobacillus were also present in the metagenome but at significantly lower abundance (<0.7%).…”

Mechanisms of arsenic attenuation in acid mine drainage from Mount Bischoff, western Tasmania

“…A green algal-like film was observed to coat the AMD sediment from the adit mouth (but only in the sunlit area) until about 30 m downstream. This is postulated to be composed of acidophilic green algae, similar to that reported by other workers studying AMD systems (e.g., Boult et al, 1997;Brake et al, 2001); further microbiological examination, however, was not undertaken.…”

Biogeochemical activity of microbial biofilms in the water column overlying uranium mine tailings

“…This was considered to be a strong indication that metal flux prediction may not be possible from physical and chemical data of a system alone; thus, information about the biofilm physiology and ecology is also required (Boult et al . ). In this study, it is suggested that biofilms located in the water column, as well as at the tailings–water interface, play an important role in the accumulation and speciation of various metals.…”