Microbial community diversity in seafloor basalt from the Arctic spreading ridges

• Published in: FEMS microbiology ecology 2004-11, Vol.50 (3), p.213-230
• Main Authors: Lysnes, Kristine, Thorseth, Ingunn H., Steinsbu, Bjørn Olav, Øvreås, Lise, Torsvik, Terje, Pedersen, Rolf B.
• Format: Article
• Language: English
• Subjects: 16S rRNA gene; Archaea; Archaea - classification; Archaea - genetics; Archaea - isolation & purification; Arctic Regions; Arctic ridges; Bacteria; Bacteria - classification; Bacteria - genetics; Bacteria - isolation & purification; Bacteriology; Basalt; Biodiversity; Biological and medical sciences; Chemical analysis; Cluster Analysis; Cold Temperature; Communities; Cultivation; Culture; Deep biosphere; Deep sea; Deep sea environments; DNA Fingerprinting - methods; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; DNA, Ribosomal - chemistry; DNA, Ribosomal - genetics; Ecology; Electrophoresis; Electrophoresis - methods; Fundamental and applied biological sciences. Psychology; Gel electrophoresis; Gene sequencing; Geologic Sediments - microbiology; Harbors; Hydrothermal systems; Iron; Iron - metabolism; Low temperature; Methanogenic bacteria; Microbial activity; Microbiology; Microbiomes; Microorganisms; Miscellaneous; Molecular Sequence Data; Nucleic Acid Denaturation; Ocean floor; Oceanic crust; Phylogenetics; Phylogeny; Polymerase chain reaction; Ridges; RNA, Ribosomal, 16S - genetics; rRNA 16S; Seawater; Sediments; Sequence Analysis, DNA; Silicates; Spreading; Water analysis
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1016/j.femsec.2004.06.014

Microbial communities inhabiting recent (⩽1 million years old; Ma) seafloor basalts from the Arctic spreading ridges were analyzed using traditional enrichment culturing methods in combination with culture-independent molecular phylogenetic techniques. Fragments of 16S rDNA were amplified from the basalt samples by polymerase chain reaction, and fingerprints of the bacterial and archaeal communities were generated using denaturing gradient gel electrophoresis. This analysis indicates a substantial degree of complexity in the samples studied, showing 20–40 dominating bands per profile for the bacterial assemblages. For the archaeal assemblages, a much lower number of bands (6–12) were detected. The phylogenetic affiliations of the predominant electrophoretic bands were inferred by performing a comparative 16S rRNA gene sequence analysis. Sequences obtained from basalts affiliated with eight main phylogenetic groups of Bacteria, but were limited to only one group of the Archaea. The most frequently retrieved bacterial sequences affiliated with the γ-proteobacteria, α-proteobacteria, Chloroflexi, Firmicutes, and Actinobacteria. The archaeal sequences were restricted to the marine Group 1: Crenarchaeota. Our results indicate that the basalt harbors a distinctive microbial community, as the majority of the sequences differed from those retrieved from the surrounding seawater as well as from sequences previously reported from seawater and deep-sea sediments. Most of the sequences did not match precisely any sequences in the database, indicating that the indigenous Arctic ridge basalt microbial community is yet uncharacterized. Results from enrichment cultures showed that autolithotrophic methanogens and iron reducing bacteria were present in the seafloor basalts. We suggest that microbial catalyzed cycling of iron may be important in low-temperature alteration of ocean crust basalt. The phylogenetic and physiological diversity of the seafloor basalt microorganisms differed from those previously reported from deep-sea hydrothermal systems.