Characterizing Microorganisms in Pillow Lava From the East Indian Ridge and From the Arctic Ridges

Microbial investigations has been carried out on basalts drilled from 10-30 Ma oceanic crust north of the Australian-Antarctic Discordance (ODP Leg 187) and dredged from the neovolcanic zones of the Mohns and Knipovich Ridges (Norwegian-Greenland Sea). The main objectives with the study are to document microbial diversity of the oceanic subsurface biosphere, and in particular to identify microorganisms participating in basalt alteration. Microorganisms in the pillow lava were characterized using enrichment techniques and DNA based methods. Cultivation experiments were started on board immediately after collecting the samples. Seawater and sediment samples were collected for comparison. The enrichment culture media were aimed at microorganisms participating in the iron, manganese, sulfur, and methane cycles. DNA, extracted directly from basalt, sediment and seawater, and from enrichment cultures, was used for PCR, DGGE and 16S rDNA sequencing. Results from enrichment studies, chemical analysis of metabolic products and DNA based techniques show that iron and manganese oxidizing and reducing bacteria, methanotrophic bacteria, and methanogenic Archaea are present in the basalt samples. These main functional groups of bacteria were found in both the 10-30 Ma drill samples and the neovolcanic dredge samples. The DNA based techniques reveal that the native basalt samples contain mostly uncultured and unidentified groups of microbes. Sulfate reducing bacteria were not abundant in the basalt samples, but were common in the seawater and sediment samples.