Tuff life: Bioalteration in volcaniclastic rocks from the Ontong Java Plateau

Abstract

[1] We report microscopic textural, geochemical, isotopic, and biomolecular evidence for microbial alteration of glass shards in a 337.7 m thick sequence of poorly sorted vitric and lithic tuffs recovered during Leg 192 of the Ocean Drilling Program on the Ontong Java Plateau. Petrographic analysis has revealed the highest density and variety of exceptionally preserved microbial alteration textures in the glass shards, when compared to previous studies of glassy pillow basalt margins from ocean crust and ophiolites. Two textural types of microbial alteration are commonly observed: tubular and granular. Tubular textures are characterized by well-preserved, micron-scale, tubular to vermicular, channel-like features with both smooth and scalloped walls that commonly extend from a granular alteration interface rimmed by clay into unaltered glass. These channels are highly convoluted or twisted and in some instances bifurcate. Detailed scanning electron microscopy (SEM) images reveal the presence of delicate filaments and desiccated thin films with morphologies suggestive of a biogenic origin within the channels. Granular textures appear as solid bands, semicircles, or irregular patches of individual and/or coalesced spherical bodies with irregular protrusions into fresh glass. Microprobe X-ray element maps show elevated levels of carbon, nitrogen, phosphorous, and potassium associated with the microbial alteration features. Bulk-rock carbon isotope ratios of disseminated carbonates in tuffs preserving fresh glass are depleted (<À9%), suggesting biologic fractionation. The presence of nucleic acids within the microbial alteration features has been confirmed though staining with ethidium bromide, a stain that specifically binds to double-stranded DNA and RNA. The presence of DNA/ RNA suggests that the biogenic features may be relatively recent and that microbes may be currently active.

Site 1256

“…In this environment, microbes colonize fractures in glassy basaltic rocks, extracting energy and/or nutrients from the glass by dissolving it and leaving behind biomarkers that reveal their former presence (Furnes and Staudigel, 1999;Banerjee and Muehlenbachs, 2003). Microbial alteration of volcanic glass has been shown to decrease with basement depth at other sites (Furnes and Staudigel, 1999).…”

“…Microbial alteration of volcanic glass has been shown to decrease with basement depth at other sites (Furnes and Staudigel, 1999). Temperature and depth limits to subbasement microbiological activity can be investigated by deep sampling and study of microbial alteration textures, chemical and isotopic indicators, and molecular microbiology (e.g., Blake et al, 2001;Alt et al, 2003;Banerjee and Muehlenbachs, 2003).…”

Prokaryotic diversity, distribution, and insights into their role in biogeochemical cycling in 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).…”

Summary of carbon, nitrogen, and iron leaching characteristics and fluorescence properties of materials considered for subseafloor observatory assembly

“…The nonspecific binding of nucleic acid stains to noncellular material has been observed previously; for example, in the binding of SYBR Green I nucleic acid stain to the mineral stalks produced by iron oxidizing bacteria in borehole colonization experiments and in the binding of SYBR Green I to debris in sediments (Morono et al, 2009). In the past, some researchers have described the presence of DNA in "microtubes" in crustal thin sections based on nucleic acid staining (e.g., Banerjee and Muehlenbachs, 2003), and have used such observations as evidence for microbial life in these microtubes. We suggest that caution must be used in such extrapolations, considering that our results show the common nonspecific binding of DNA stains to dopes and other materials that would be used during the drilling process used to collect the hard rock samples.…”