Ultrabasic Spring Geomicrobiology of the Cedars Peridotite

Peridotite hosted aquifers are becoming well-known as a modern analog for both extraterrestrial and early- Earth habitats despite relatively few studies on microbes in ultramafic systems. To investigate the microbiology associated with aquifers of the actively serpentinizing Cedars Peridotite in coastal Northern California an interdisciplinary approach involving molecular phylogenetics, organic and inorganic geochemistry, as well as culture-based ecophysiological methods are being utilized. Based on our findings, Cedars spring microorganisms endure one of the harshest low-temperature aqueous environments on Earth with pH greater than 11.8, Eh less than -600 mV, undetectable dissolved CO2 and O2 and a lack of other obvious e- acceptors. Despite these conditions, life inhabits solid substrate surfaces within the springs to a concentration of 10E6-10E7 cells/sq. cm, but planktonic cell densities are extremely low (much less than 10E3/ml). Preliminary 16S data of 3 ultrabasic fluids reveals a community comprised primarily of bacteria that appears to be of low-diversity. Methanogens are strongly suggested to be present based on the isotopic composition of methane bubbling from the springs, but have not yet been identified via molecular techniques. Community level metagenomic sequencing of the ultrabasic spring microorganisms sampled from peridotite-associated mineral surfaces and glass slides incubated in specially designed flow- through chambers are currently in-progress and are likely to reveal several novel metabolic pathways.