HR: 1400h
AN: B13B-04    [Abstracts]
TI: Microbial ecology of a novel sulphur cycling consortia from AMD: implications for acid generation
AU: * Loiselle, L M
EM: loisellm@mcmaster.ca
AF: School of Geography and Earth Sciences, McMaster University, 1280 Main St W, Hamilton, ON L8S 4K1, Canada
AU: Norlund, K L
EM: norlunkl@mcmaster.ca
AF: School of Geography and Earth Sciences, McMaster University, 1280 Main St W, Hamilton, ON L8S 4K1, Canada
AU: Hitchcock, A P
EM: aph@mcmaster.ca
AF: Brockhouse Institute for Materials Research, McMaster University, 1280 Main St W, Hamilton, ON L8S 4M1, Canada
AU: Warren, L A
EM: norlunkl@mcmaster.ca
AF: School of Geography and Earth Sciences, McMaster University, 1280 Main St W, Hamilton, ON L8S 4K1, Canada
AB: Recent work¹ identified a novel microbial consortia consisting of two bacterial strains common to acid mine drainage (AMD) environments (autotrophic sulphur oxidizer Acidithiobacillus ferrooxidans and heterotrophic Acidiphilium spp.) in an environmental enrichment from a mine tailings lake. The two strains showed a specific spatial arrangement within an EPS macrostructure or "pod" allowing linked metabolic redox cycling of sulphur. Sulphur species characterisation of the pods using scanning transmission X-ray microscopy (STXM) indicated that autotrophic tetrathionate disproportionation by A. ferrooxidans producing colloidal elemental sulphur (S⁰) is coupled to heterotrophic S⁰ reduction by Acidiphilium spp. Geochemical modelling of the microbial sulphur reactions indicated that if they are widespread in AMD environments, then global AMD-driven CO₂ liberation from mineral weathering have been overestimated by 40-90%¹. Given the common co-occurrence of these two bacteria in AMD settings, the purpose of this study was to evaluate if these pods could be induced in the laboratory by pure strains and if so, whether their combined sulphur geochemistry mimicked the previous findings. Laboratory batch experiments assessed the development of pods with pure strain type cultures (A. ferrooxidans ATCC 19859 with mixotroph Acidiphilium acidophilum ATCC 738 or strict heterotroph Acp. cryptum ATCC 2158) using fluorescent in situ hybridization (FISH) imaging. The microbial sulphur geochemistry was characterized under autotrophic conditions identical to those used with the environmental AMD enrichment in which the pods were discovered. Results showed that the combined pure strain A. ferrooxidans and Acp. acidophilum form pods identical in structure to the AMD enrichment. To test the hypothesis that these pods form for mutual metabolic benefit, experiments were performed amending pure strain and AMD enrichment bacterial treatments with organic carbon and/or additional sulphur to assess whether or not pods formed and/or disassociated under non-competitive and/or non-nutrient limiting scenarios. The results of these experiments will be presented and their ecological and AMD sulphur geochemical implications discussed.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0448 Geomicrobiology
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0488 Sulfur cycling
SC: Biogeosciences [B]
MN: 2009 Joint Assembly