Microbial diversity in low temperature iron deposits at the 71°N hydrothermal vent field at the arctic-ocean ridge

Category Mineral processing
Group GSI.IR
Location International Geological Congress,oslo 2008
Author طvreهs, Lise; Johannessen, Torill Vik; Einen, Jّrn; Jّrgensen, Steffen Leth; Thorseth, Ingunn; Pedersen, Rolf Birger
Holding Date 28 September 2008

Rust coloured mounds and chimney-like deposits of the newly discovered hydrothermal vent fields at the Mohns Ridge have been studied. This vent field represents the northernmost known hydrothermal vent field along the Mid-Atlantic Ridge Large areas of the vent field are dominated by low temperature iron mound formations. Iron has always played an important role in life’s history, and microbial iron oxidation is a widespread process in the deep sea environments. There is, however, only limited knowledge about iron oxidation as an ancient metabolic pathway, and few isolates have yet been cultivated. Phylogenetic analysis of bacterial clone library evidenced a large diversity of uncultured bacteria within the a, b,d and g-proteobacteria and also Bacterioidetes, Planctomycetes, Green Non Sulfur bacteria (GNS), Actinobacteria, Verrucomicrobium and TM6. The numerically abundant groups were the d-proteobacteria, Planctomycetes and GNS. By contrast the archaeal diversity detected was fairly low. Both Euryarchaeota and Crenarchaeota sequences were retrieved. A major clade within the Crenarchaeota was dominated by one phylum closely related to the newly described ammonia oxidizer "Nitrosopumilus maritimus". To further investigate the role of these iron mounds into the ecosystem and their interaction with microorganisms, cultivation experiments were applied. We are specifically focusing on enrichment of iron oxidizers using FeS as substrate in liquid and semisolid media as well as gradient plates.
The gradient plates gave the highest amount of biomass in the enrichments. Dominant members in the enrichment cultures showed closest phylogenetic affiliation (97% identity) to the newly described Mariprofundus ferrooxidans which is a novel lineage of proteobacteria involved in formation of Marine Fe-oxidizing microbial mat communities. Data from the clone library failed to retrieve sequences from any known iron oxidizers. Iron reducers related to Rhodoferax ferrireducens were also present in the enrichments from these environments. Strains isolated from these systems will provide an opportunity to explore the phylogenetic diversity of neutrophilic Fe metabolism and to establish model systems for molecular metabolic studies.