Evidence of biological activity in Hawaiian subsurface basalts

Abstract

[1] The Hawaii Scientific Drilling Program (HSDP) cored and recovered igneous rock from the surface to a depth of 3109 m near Hilo, Hawaii. Much of the deeper parts of the hole is composed of hyaloclastite (fractured basalt glass that has been cemented in situ with secondary minerals). Some hyaloclastite units have been altered in a manner attributed to microorganisms in volcanic rocks. Samples from one such unit (1336 m to 1404 m below sea level) were examined to test the hypothesis that the alteration was associated with microorganisms. Deep ultraviolet native fluorescence and resonance Raman spectroscopy indicate that nucleic acids and aromatic amino acids are present in clay inside spherical cavities (vesicles) within basalt glass. Chemical mapping shows that phosphorus and carbon were enriched at the boundary between the clay and volcanic glass of the vesicles. Environmental scanning electron microscopy (ESEM) reveals two to three micrometer coccoid structures in these same boundaries. ESEM-linked energy dispersive spectroscopy demonstrated carbon, phosphorous, chloride, and magnesium in these bodies significantly differing from unoccupied neighboring regions of basalt. These observations taken together indicate the presence of microorganisms at the boundary between primary volcanic glass and secondary clays. Amino acids and nucleic acids were extracted from bulk samples of the hyaloclastite unit. Amino acid abundance was low, and if the amino acids are derived from microorganisms in the rock, then there are less than 100,000 cells per gram of rock. Most nucleic acid sequences extracted from the unit were closely related to sequences of Crenarchaeota collected from the subsurface of the ocean floor.

Prokaryotic diversity, distribution, and insights into their role in biogeochemical cycling in marine basalts

“…This is the first report of this clade in this environment, as previous studies that examined the archaeal communities in basalts revealed only Marine Group I Crenarchaeota Fisk et al, 2003;Lysnes et al, 2004;Mason et al, 2007). Recently, quantitative analyses of the microbial communities in basalts revealed that Archaea comprise 4-12% and 0.02% or less of the prokaryotic communities (Santelli et al, 2008;Einen et al, 2008), respectively.…”

“…Although these estimates are disparate, they do reveal that Archaea are a minor component in the overall microbial communities that reside in basalt. Although Archaea are less prevalent, they are ubiquitous in basalts and have been reported in all studies that assayed for their presence Fisk et al, 2003;Lysnes et al, 2004;Mason et al, 2007;Einen et al, 2008;Santelli et al, 2008). Further, as discussed previously, a clade of Marine Group I Archaea appears to be endemic to basalt (Mason et al, 2007).…”

“…Methanogens have not been reported in molecular analyses of Archaea in basalts conducted to date Fisk et al, 2003;Lysnes et al, 2004;Mason et al, 2007). However, Lysnes et al (2004) reported that methane was evolved in enrichment cultures inoculated with marine basalts.…”

“…These observations raise intriguing questions about the role that microorganisms play in biogeochemical cycling in basalts. Biological alteration of basalt by microorganisms has been the focus of numerous studies, with compelling evidence suggesting that they do play a part in this process (Thorseth et al, 1995;Giovannoni et al, 1996;Fisk et al, 1998Fisk et al, , 2003Torsvik et al, 1998;Furnes and Staudigel, 1999;Furnes et al, 2001Furnes et al, , 2004Banerjee and Muehlenbachs, 2003).…”

Deep Drilling into a Mantle Plume Volcano: The Hawaii Scientific Drilling Project

“…The alteration process may be significant in understanding the reactions and compositional exchange between seawater and basalt glass at low temperatures, thereby providing an analogue system for the early history of fluids that circulate through mid-ocean hydrothermal systems. Signs of microbial involvement in the alteration process are evident as filamentous channels in glass, but only within a restricted portion of the core between about 1080 mbsl and 1460 mbsl (Walton and Schiffman, 2003;Walton, 2008;Fisk et al, 2003). This re-striction suggests that microbes infected the hyaloclastites early in their history but are not very active at present.…”