Goldschmidt Conference Abstracts 2005 Geomicrobiology
A833
Preferential adhesion of rough phenotypes to iron oxides from heterogeneous DMRB populations
Epi- and endo-lithic bacterial colonisation of aeolian sandstone on the Colorado Plateau
A. KORENEVSKY1, O. STUKALOV2, J. DUTCHER2 1 AND T. BEVERIDGE
K. HUGHES AND G. SOUTHAM
The rate of iron oxide reduction by dissimilatory metalreducing bacteria (DMRB) depends on bacterial adhesion to the mineral surface. Adhesion is governed by physicochemical interactions at the cell-mineral interface. It was shown that adhesion of DMRB, Shewanella, to iron oxides is determined by polysaccharide (PS) components of the outer membrane. O-side chains of LPS and capsular PS of smooth strains inhibited bacterial adhesion while rough strains (no PS extending from the surface) adhered well. TEM and AFM revealed that populations of DMRB such as Geobacter and Shewanella displayed varying degrees of phenotype heterogeneity in terms of cell surface structure and composition: both rough and smooth cells were present within the same population. Adhesion of DMRB to different minerals and model substrates was assessed using AFM and fluorescent microscopy. It was found that the mineral surface physicochemical properties determine its selectivity towards certain phenotypes of bacterial cells. Rough phenotypes adhered better to positively charged (e.g., iron oxide) and hydrophobic surfaces, while smooth phenotypes adhered better to hydrophilic surfaces (mica, glass). Moreover, in the case of overall smooth DMRB populations (S. oneidensis MR4 or S. algae FC), only rough cells were found on the surface of the iron oxide. Such phenotypic plasticity, when a certain amount of adhesive cells is always present in the population, ensures an ecological advantage for DMRB in a variety of subsurface environments.
Dept. of Earth Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5B7 (
[email protected],
[email protected]) Harsh semi-arid environments such as those found on the Colorado Plateau in Southern Utah require unique adaptations of the indigenous life. This study concerns bacterial communities that act as pioneer organisms ultimately allowing exposed sandstone surfaces to be colonised by higher organisms. These bacterial communities interact with the substrate to produce round weathering features termed “pot holes” which support ephemeral life durring the rainy season. The bacteria are typically found, as a black (desiccated) epilithic biofilm that lines the potholes, as a cryptoendolithic biofilm centimeters below the rock surface and, eventually in the thin sediment layers that accumulate at the bottom of some potholes. Growth of these biofilms under oligotrophic conditions has been established through a series of field experiments that involved wetting the potholes with deionized water and monitoring the resulting geochemical activity.
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Department of Cellular and Molecular Biology, 2Department of Physics, University of Guelph, Guelph, Ontario, N1G 2W1, Canada (
[email protected])
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Figure 1: Diurnal cycling of P and pH over 4 days. The examination of petrographic sections, and the use of high resolution structural techniques, i.e., focused ion beam sectioning FIB-SEM and atomic force microscopy, have demonstrated an intimate association between the biofilms and the arenitic sandstone host, and were used to follow the development of the biofilm when wetted with deionised water. As the pioneer species, these microbial biofilms serve a terraforming role in this extreme environment where higher organisms, i.e., plants and animals, can eventually survive.
A834
Goldschmidt Conference Abstracts 2005 Geomicrobiology
Microbial metabolic diversity in deep sedimentary rocks of a foreland basin, Taiwan LI-HUNG LIN1, PEI-LING WANG2, HON-TSEN YU1, TING-WEN CHENG1, SHENG-RONG SONG3 4 AND CHIEN-YING WANG
Carbon dioxide sequestration through enhanced weathering of chrysotile mine tailings and subsequent microbial precipitation of magnesium carbonates I. POWER AND G. SOUTHAM
1
Institute of Zoology, National Taiwan University, Taipei, Taiwan (
[email protected]) 2 Institute of Oceanography, National Taiwan University, Taipei, Taiwan 3 Department of Geosciences, National Taiwan University, Taipei, Taiwan 4 Department of Earth Sciences and Institute of Geophysics, National Central University, Taiwan Terrestrial subsurface microbial niches have been greatly extended to various enviroments that were previously thought barren of any life form. These ecosystems, including deep sedimentary aquifers, petroleum reservoirs, and igneous intrusions, are characterized by compartment of fracture network where the water activity and substrate flux are greater than those in rock matrix. The groundwater transport, however, is extremely slow, limiting the substrate influx derived from surface photosynthesis and exhchange between different reservoirs. Microbial populations are potentially self-sustainable, relying upon geologically-produced substrates. Contrary to those in stable continental crust, microbial communities and channel for substrate transport are frequently disrupted in active tectonic environments (such as subduction zone) and remain poorly constrained. The Taiwan Chelunpu Drilling Project has provided an unprecedented opportunity to reveal the terrestrial subsurface microbial ecosystem that may have experienced constant disturbance by the arc-continent collision since 5 Ma. The drilling penetrated through the Pleistocene-Pliocene sedimentary rocks to a depth of 2000m below land surface (mbls). Two major fracture zones with ~100 m thickness were encountered at depths of ~1100 and ~1750 mbls, respectively. Among 25 samples retrieved from the rock formations or within the fracture zones along the depth profile, 15 were ground to powders, inoculated to media designed for fermenter, iron reducer, sulphate reducer and methanogen, and incubated at temperatures ranging from 30 to 70oC. Mesophilic and thermophilic fermenters and organotrophic sulphate reducers were ubiquitously present in most samples, whereas iron reducers and methanogens appeared only at the samples from the upper (400-700 mbls) and lower portions (1800-1900 mbls) of the drilled cores. The presence of metabolisms is not correlated with lithology, depth, temperature and fracture.
Department of Earth Sciences, The University of Western Ontario, London, Ontario, Canada, N6A 5B7 (
[email protected]) Magnesium silicate minerals naturally weather and release magnesium ions, which may participate in carbon dioxide sequestration through the precipitation of carbonate minerals (Goff and Lackner, 1998). However, this dissolutionprecipitation reaction is kinetically slow under ambient surface conditions. Column leaching experiments were developed to evaluate the use of acid generating substances in dissolving chrysotile mine tailings, collected from Clinton Creek, YT. The addition of elemental sulphur or sulphide-rich mine tailings in conjunction with acidophilic sulphur or iron oxidizing bacteria, respectively, enhanced the release of magnesium by up to twenty five times over control systems. Biological columns were shown to significantly increase the rate of dissolution by accelerating the oxidation of these acid generating substances. It was also demonstrated that chrysotile tailings are efficient in neutralizing acidic leachates, which resulted in the precipitation of the associated metals (iron, copper, zinc) within the columns. Ferris et al. (1994) demonstrated that oxygenic photosynthetic bacteria can catalyze the formation of magnesium carbonate minerals, thereby consuming carbon dioxide. Cyanobacteria, added to a collection of magnesiumrich waters, raised the pH resulting in the oversaturation of magnesium carbonate and subsequent precipitation of carbonate minerals. These results suggest that magnesium-rich mine tailings may be utilized as carbon sinks by accelerating dissolution through the addition of acid generating substances coupled with microbially catalyzed precipitation of carbonate minerals.
References Goff F. and Lackner K.S., (1998), Environ. Geosci. 5:89-101. Ferris F.G., Wiese R.G. and Fyfe W.S., (1994), Geomicrobiol. 12:1-13.
Goldschmidt Conference Abstracts 2005 Geomicrobiology
Cyanobacteria Fossils from Neo-Archaean Chitradurga Schist Belt: Evidence of a bioherm T. GNANESHWAR RAO AND S.M. NAQVI National Geophysical Research Institute, Hyderabad–500007, India (
[email protected]) The Chitradurga Schist Belt (CSB) is a volcano sedimentary sequence comprising of polymodal metavolcanics, greywackes, banded iron formations (BIFs), shales, and carbonates + stromatolites. These are intruded by Chitradurga granite dated at 2.6 Ga [1]. The different facies of BIFs such as oxide, carbonate, sulphide and mixed facies occur in the central part of CSB in various lithological associations [2]. The carbonate facies banded iron formations (CBIFs) are associated with amphibolite, stromatolite, carbonaceous chert, manganiferrous carbonate and phyllite interlayered metavolcanics are dated at 2.7 Ga. Petrographic and Microprobe studies revealed that these CBIFs are mainly made up of siderite, ankerite, ferron-dolomite, dolomite, calcite, magnesium siderite. Micro-filaments and bioherms are observed in carbonate facies BIFs and these microfilments are mostly found near the bedding planes between the chert and carbonate rich layers. They are usually concentrated in the carbonate rich layers and appear to be similar to the bioherms reported from associated rocks of Proterozoic BIF. The syngenetic nature of these filaments is clearly evident in the samples wherein the filaments are seen cutting across the carbonate grains (Figure 1).
Figure 1 Figure 2 The presence of stromatolites (Fig.2) and the δ C 13 values (-16‰, -17‰ and -12‰) of the carbon rich fractions separated from samples confirms their organic nature.
References [1] Bhaskar Rao, Y.J., Sivaraman, T.V., Pantulu, G.V.C., Gopalan, K. and Naqvi, S.M., (1992), Precamb. Res. 59(12). 145-170. [2] Gnaneshwara Rao, T. and Naqvi, S.M., (1995), Chem. Geol. 121. 217-243.
A835
Structural and chemical characterization of a natural fracture surface from 2.8 kilometers below land surface G. WANGER AND G. SOUTHAM Department of Earth Sciences, The University of Western Ontario. London, ON. Canada N6A 5B7 (
[email protected],
[email protected]) The ultra-deep gold mines located in the Witwatersrand basin, Republic of South Africa offer unprecedented access to the terrestrial deep subsurface. A water bearing fracture, intersected by an advancing tunnel 2.8 kilometres below land surface, was investigated and samples of the fracture surface were collected soon after the tunnel was extended through the feature. Micro X-Ray diffraction demonstrated that the fracture material (approximately 1 mm thick) coating the fracture surface consisted of chamosite with other chlorite group minerals as secondary phases. Using Scanning Electron Microscopy, the surface was found to be colonized by small, highly dispersed ‘microcolonies’ of bacteria containing between 1 and 5 cells/microcolony. Some microcolonies were adsorbed to the fracture surface via exopolysaccharide material while others were not. Cell densities were determined to be 5x103 cells/cm2 adsorbed to the surface and 5x104 cells/ml in the fluid phase. Using a 100 µm thick in situ fracture void, the ‘biofilm’ population is 2 orders of magnitude greater than the cell density in the fluid phase. Water analysis and energetics calculations reveal abundant nutrient and energy availability, suggesting that more bacteria should have been observed in these samples. Also, Time of Flight – Secondary Ion Mass Spectrometry (ToF-SIMS) of the fracture surface revealed that a most of the fracture surface was coated with a molecular-scale organic conditioning film separate from the exopolysaccarides associated with some of the microcolonies. This environment, then possesses even more ‘nutrients’ than measured in the aqueous phase. The observation that the subsurface biosphere is “underpopulated” is supplemented by the presence of large scale biofilms (mine slimes), which develop on the tunnel walls where subsurface water encounters the oxygenated mine environment.
