Dr. Kurt Konhauser  Department of Earth and Atmospheric Sciences  University of Alberta, Edmonton  Alberta, T6G 2E3  phone: 780-492-2571  fax:      780-492-2030  Email: kurtk@ualberta.ca Editor-in-Chief of Geobiology Author of "Introduction to Geomicrobiology",  published by Blackwell, Oxford

(1) Current Research Interests

(2) Recent Publications

(3) Research Group
 
 

Current Research Interests

I am now in the process of continuing this work in Yellowstone National Park, USA with Dr. Bill Inskeep (Montana State) to ascertain the microbial influences on both silica and iron hydroxide precipitation under varying geothermal conditions. Natural sinter and effluent samples have been collected to characterize the dominant microflora, their activities and their relative importance in constructing the various sinter fabrics via biomineralization and growth patterns. This work will be linked to current studies on the origins of laminations in Archean stromatolites and on the mechanisms responsible for the fossilization of Archean microbial mats.

Hot spring at Krisuvik, Iceland                                       Sinter laminations, comprising silica (white) and                    SEM image of the silica layers (white) overlain by the
                                                                                             microbial (green) layers.                                                              microbial layers which consist of vertically-aligned,
                                                                                                                                                                                                     filamentous cyanobacteria.
 

2. Bacterial Silicification
Silica precipitation is an important geological process in many modern geothermal systems, where venting of supersaturated solutions leads to the formation of siliceous sinters around geyser vents. Early studies considered it to be an entirely passive inorganic process, however, attempts to reproduce inorganic conditions in the laboratory usually generate precipitation rates that are orders of magnitude slower than those recorded in nature. This discrepancy may be the result of microbial activity, and many recent studies at hot springs have shown that microbes facilitate silicification over a range of temperatures. During silicification, some cells become so encrusted that their organic residues remain intact after lysis, i.e., as microfossils. To ascertain the sites of silicification we artificially subjected the cyanobacterium Calothrix to silica supersaturated solutions. Examination by transmission electron microscopy (TEM) revealed mineralization of intact cells only occurred upon the extracellular sheath. No intracellular mineralization was observed. In addition, polycationized ferritin (a probe 11 nm in diameter) labelled the sheath's outer surface but failed to penetrate the sheath matrix, indicating its impermeablity to particles of this size and greater. Phoenix et al. (1999)subsequently proposed a model to explain the restriction of silicification to the outer surface of the sheath. We suggested that cyanobacterial photosynthesis creates a moderately alkaline environment (pH 7-9) adjacent to the sheath, causing silica to form colloids. These colloids are too large to penetrate the sheath, and hence mineralization is restricted to the outer surface. It was further proposed that the partial diffusion barrier created by the sheath allows very high photosynthetically induced pH levels (> pH 10) to build up inside the sheath matrix. Under these conditions silica is both highly soluble and in its monomeric state, and is thus less able to bind to the sheath matrix. To further test if the cells survived silicification, we measured the autofluorescence of the encrusted cells and found that their pigmentation remained intact. Their viability was confirmed by oxygen electrode analysis which showed that the mineralized colonies were photosynthetically active. Moreover, they exhibited comparable rates of photosynthesis to the non-mineralized colonies, suggesting mineralization was not notably detrimental to the microorganisms (Phoenix et al., 2000).

Light microscopy image (left) and fluorescent image (right) of Calothrix filaments after                                       TEM micrograph of a cluster of silicified Calothrix
silicification. The fluorescence indicates that mineralized cells are pigmented and still viable.                              filaments. The cluster is encompassed in a continuous
Scale bar is 75 microns,  X is filament.                                                                                                                              silica matrix (arrow). Scale Bar is 5 microns.

These observations also have important consequences for the Precambrian. Many models of atmospheric evolution predict that the Archean atmosphere contained insufficient oxygen to form an effective ozone screen. Under such unfavourable conditions, early life forms must have used several different lines of defense, including vertical migration strategies, the production of shielding pigments or a variety of photo-repair mechanisms. However, we proposed a new alternative, i.e., that bacteria naturally precipitated iron-silicate minerals, which fortuitously afforded them with UV protection (Phoenix et al., 2001). This experimental study made two exciting and completely novel observations. First, it showed that cyanobacteria could survive the processes of iron-silicate biomineralization, even when some filaments were encrusted in a mineral coating several micrometers thick. Second, we documented that the mineral coatings provided them with nearly 100% protection against UV-C; unmineralized cells quickly died. This work has broad implications for the evolution of primitive life because it speculates that the UV-shielding capacity of iron-silicate biominerals may have allowed colonization and bacterial diversification of shallow water environments. Moreover, understanding the mechanisms and salient physico-chemical features associated with bacterial silicification may ultimately lead to a better understanding of what species comprised Earth's earliest microfossil assemblages (Konhauser et al., 2003).

Another area of current research is ascertaining the kinetics and physicochemical processes associated with microbial silicification. Preliminary laboratory studies conducted in Leeds showed that the polymerization of silica-supersaturated solutions occurs rapidly, and that microbial biomass (Calothrix) does not exert a significant effect on its rate (Yee et al., 2003). These findings have since been duplicated using the thermophilic chemolithoautotrophic bacterium, Sulfurihydrogenibium Azorense (Lalonde et al., 2005). In fact, at high silica levels there is such a strong chemical driving force for homogeneous nucleation and silica precipitation that there is no obvious need for microbial catalysis. Therefore, biogenic silicification at hot springs occurs simply because microbes grow in a polymerizing solution where silicification is inevitable. With that said, however, there are species-specific patterns of silicification because different microbes are certainly capable of being silicified with different degrees of fidelity.  This is not surprising given that the actual mechanisms of silicification rely, in part, on the microorganisms providing reactive surface ligands that adsorb silica from solution, and accordingly, reduce the activation energy barriers to heterogeneous nucleation (Konhauser et al., 2004).  This means that cell surface charge may have a fundamental control on the initial silicification process. For example, Phoenix et al. (2002) showed that the sheath of Calothrix is electrically neutral at pH 7, comprising predominantly neutral sugars, along with smaller amounts of negatively-charged carboxyl groups and positively-charged amine groups, in approximately equal proportions. On the one hand, the low reactivity of Calothrix’s sheath gives the cells hydrophobic characteristics that facilitate their attachment to solid submerged substrata, e.g., siliceous sinters. On the other hand, this same property makes the sheath material less inhibitive to interaction with the colloidal silica fraction in solution. Silicification subsequently occurs through hydrogen bonding between the hydroxy groups associated with the sugars and the hydroxyl ions of the silica (Benning et al., 2002; Benning et al., 2004). In contrast, the highly anionic nature of Bacillus subtilis limits silicification from occurring on its cell wall, likely as a result of electrostatic charge repulsion between the organic ligands and the negatively-charged silica colloids (Phoenix et al. 2003).  For silicification to proceed, cation bridging (e.g., Fe³⁺) is required. More recently, electrostatic interactions between silica and protein-rich biofilms that contain cationic amino groups has also been shown as an important silicification reaction in some species (Lalonde et al., 2005).

Current experiments are being run in order to assess whether the cell surface charge is modified during the process of silicification, and even if the  composition of the cell's outer surface functional groups change in response to growing in silica-rich fluids. This work is in collaboration with Anna-Louise Reysenbach (Portland State), George Owttrim (UofA) and Stefan Lalonde (UofA PhD student).
 

3. Microbial Mat Surface Chemistry
Significant efforts have been made to elucidate the chemical properties of bacterial surfaces for the purposes of refining surface complexation models that account for their metal sorptive behaviour. Recently, my students and I employed potentiometric titrations to evaluate variations in bacterial surface organic functional group chemistry using live cells of the cyanobacterium Anabaena sp., grown under a variety of batch culture conditions, and by various assimilatory nitrogen metabolisms. We observed that ligand concentrations and acidity constants were influenced by the form of nitrogen on which the cultures grew, as well as their stage of growth (Lalonde et al., in revision(a)). Subsequently, we grew the cells in solutions of varying ionic strength and silica concentrations, and additionally showed that the cells altered their surface chemistry as a response to growth in silica supersaturated solutions (Lalonde et al., in revision(b)). Collectively, these two studies highlighted the complexity of microorganism-environmental interactions in terms of cell reactivity, demonstrating that a single bacterial species may alter its surface chemical properties in response to environmental stimuli. In a logical progression, we applied cell surface characterization techniques to natural microbial populations at hot springs in Yellowstone National Park. In the first study, we evaluated the concentrations and thermodynamic properties of surface ligands associated with microbial mats and hydrous ferric oxides (HFO), the concentrations of metals that they bound, and the chemical composition of the fluids in which they were bathed. Consideration of all three parameters has allowed, for the first time, a direct comparison between organic and inorganic surface chemical reactivity and metal sorptive capacity in the same natural setting. We showed that microbial and HFO surfaces have similar concentrations of surface ligands that are available to serve as sorption and mineral nucleation sites, yet those sites differ in their affinity for specific elements as a function of their chemical composition (Lalonde et al., 2007a). In a second study, we collected a number of microbial mat samples from a single spring, with the goal being to ascertain differences in cell surface reactivity on small spatial scales. We showed significant variability in surface chemical reactivity between microbial communities on scales of just a few millimeters; much of that variability was due to the ratio of cells to extracellular polymers (EPS). We also demonstrated that in these mats, the presence of authigenic carbonate phases (that formed during photosynthetically-generated alkalinization) intermixed with the EPS played a greater role in metal partitioning than the organic components of the mat ecosystem (Lalonde et al., 2007b).

Despite the recent accomplishments by my laboratory and others, there remain many unanswered questions regarding the various chemical reactions occurring at the cell surface. For instance, predictive surface complexation models rely on previously determined metal-stability constants for the accurate description of sorptive processes in complex aquatic systems, however, metal-stability constants intrinsic to the bacterial surface have yet to be determined using natural microbial biomass. Accordingly, in collaboration with Drs. Bill Inskeep and Tim McDermott, Montana State University, as well as Stefan Lalonde (UofA PhD student), we have collected microbial mat samples from hydrothermal systems in Yellowstone National Park for the purpose of batch metal-sorption experiments that will allow for the derivation of ligand-metal stability constants. Not only will this data serve to verify, or deny, decades of experimental results obtained using laboratory cultures, but it will also facilitate the refinement of predictive models describing the sequestration of metals by microbial surfaces. By extension, existing bioremediation strategies will stand to benefit from our increasing ability to account for the sorption of heavy metals and other pollutants by microbial biomass. Field studies will be complemented by laboratory experiments further exploring the control a microorganism has on the chemical properties of its own surface. In a collaborative effort with Dr. George Owttrim (UofA), we are investigating the surface reactivity of the cyanobacterium, Anabaena sp. PCC 7120.
 

4. Banded Iron Formations
Banded iron-formations (BIFs) are prominent sedimentary deposits of the Precambrian, but despite a century of endeavour, the mechanisms for iron deposition remain unresolved. Unlike most existing models, which rely on photochemical processes or inorganic reactions between Fe²⁺ and O₂, my colleagues and I were the first to show quantitatively that direct chemolithotrophic or photoferrotrophic Fe(II) oxidation had the potential to generate the bulk, if not all, of the ferric iron in BIF (Konhauser et al., 2002). The model was based on chemical analyses of BIF core from the 2.5 Ga Dales Gorge Member of the Hamersley Group, Western Australia. Not only did we calculate the number of metabolizing cells required to form an annual BIF deposit, but we also showed that there were sufficient nutrients and trace metals available in the BIF to support their growth. Subsequently, we demonstrated experimentally that photoferrotrophs, using radiation at wavelengths that penetrate to 100 meters depth in the water column, and at only 1% surface irradiance, could still generate enough Fe(III) to account for all the Fe in BIF (Kappler et al., 2005). By ascertaining the amount of biomass generated phototrophically in the water column, with the amount of Fe(II) in BIF, we then further established the direct link between surface productivity in an Archean ocean, and the number of reducing equivalents needed for magnetite formation during sediment diagenesis (Konhauser et al., 2005). Importantly, our calculations further suggest a complex microbial community likely existed on the Archean seafloor, comprising fermenters, Fe(III) reducers, methanogens and methanotrophs, the latter possibly coupling Fe(III) reduction to methane oxidation (a novel metabolism). We have also analyzed for trace metal/Si ratios in various mesobands of the Dales Gorge Member to ascertain whether the silica is continentally or hydrothermally derived (Hamade et al., 2003). For silica-rich and varved mesobands we show that the ratios fall within the continental end member range, suggesting weathering of landmass as the predominant source for silica in these mesobands. However, when ratios are measured in Fe-rich mesobands, they reflected a hydrothermal input. This confirms that the sources of silica and iron were decoupled during BIF deposition. Moreover, significant variation between different mesobands (representing tens of thousands of years) indicate that the ratios were not at steady state during the Precambrian.

Recently, my students and I have also re-assessed the photochemical oxidation process through a combination of thermodynamic modelling and photooxidation experiments using mixed, saline fluids that mimic the Archean oceans. We showed that mineral precipitation along the plume flow pathway would have critically diminished the amount of dissolved Fe(II) that could have been supplied into the photic zone (Konhauser et al., 2007a). Even if Fe(II) originated from a shallow seamount-type vent system directly into the photic zone, the photochemical contribution to solid-phase precipitation might only have been a few tens of percent. Crucially, if the bulk of Fe minerals in BIF were precipitated as reduced phases, then it becomes difficult to accept BIF as a proxy for photooxidation. This work is being combined with another study (in collaboration with Ariel Anbar, Arizona State and Nicolas Dauphas, University of Chicago) on Fe isotopic fractionations demonstrating that isotopically heavy Fe is preferentially removed from solution during photooxidation at low pH. The preliminary findings are also showing that the magnitude of isotope fractionation during photooxidation changes at higher pH for two reasons. First, ferric hydroxide precipitation, which imparts a kinetic isotope effect, is faster at higher pH. Second, the major photolyzing ferrous ion species in the ocean is Fe(OH)⁺, the concentration of which is strongly pH dependent.

During Archean-Paleoproterozoic BIF deposition, it has also been suggested that particles of ferric oxyhydroxide settling to the seafloor may have stripped dissolved phosphate from the photic zone. This would have led to a diminishment of phytoplankton activity, which in turn, was manifest by lower rates of organic carbon burial. This model, however, does not take into account the high concentration of dissolved silica present in the ancient oceans. In a recent paper, we demonstrated that silica out-competes phosphate for reactive sites on ferrihydrite surfaces, while silica incorporation into the mineral structure leads to a lowering of the particle’s point of zero charge and affinity for phosphate (Konhauser et al., 2007b). Iron-silica-phosphate co-precipitation experiments described in the paper strongly suggest that contrary to popular belief, ferric oxyhydroxide particles would not have sequestered phosphate in significant amounts, and phosphate was not limited as a nutrient in Earth’s early oceans. Furthermore, we have conducted detailed geochemical analyses of all the diagenetic minerals in the Dales Gorge BIF, and have revealed that the iron oxide phases do not contain significant phosphate, but instead, it is contained within apatite and carbonates (Pecoits et al., in review(a)).
 
 

Future work on Archean-Paleoproterozoic BIFs will be conducted on two fronts, namely (i) the mechanisms of oxidation and (ii) understanding BIF diagenesis.

(i) Despite our recent publications, the mechanisms of BIF deposition are still an area of great uncertainty. One current analytical technique that may shed light on this question is the evaluation of ⁵⁶Fe/⁵⁴Fe isotopic ratios of experimentally precipitated Fe minerals, followed by comparison of those values with actual BIF samples. As discussed above, we are currently examining the fractionation associated with inorganic photochemical oxidation to ascertain whether similar reactions occurred in the Archean, prior to the onset of an ozone-rich atmosphere. Photooxidation experiments under increasingly complex solutions, that better mimic Precambrian seawater, will be the subject of future investigation. Two students are working on this topic; Larry Amskold, a PhD student at UofA and Sarah Straton, a PhD student at Arizona State.

(ii) During deposition of BIFs the downward flux of ferric hydroxide and phytoplankton biomass should have facilitated microbial Fe(III) reduction. Although estimates can be made regarding the quantity of reducing equivalents necessary to account for the diagenetic Fe(II) component in Fe-rich, oxide-type BIF layers, those same estimates do not offer any insights into the magnitude of Fe(III) actually generated within the water column, and hence, the efficiency of Fe and C recycling prior to burial. Accordingly, in collaboration with Andreas Kappler (University of Tuebingen) and Nicole Poste (Tuebingen PhD student), we are trying to develop a better understanding of the link between primary productivity in the Precambrian ocean and the diagenetic processes that later altered BIF mineralogy.
 

5. Sediment Diagenesis
Sediments have distinct biogeochemical zones that develop in response to the amount of labile organic carbon buried, sedimentation rates, the availability of different terminal electron acceptors, grain size and permeability. However, the idealized vertical zonation can be disrupted by the burrowing activity of invertebrates. This process, known as bioturbation, causes millimetre- to centimetre-scale biogeochemical heterogeneities that form as a result of particle remobilization, redox oscillation, excretion, irrigation and grazing of indigenous microorganisms and other organic substrates. Importantly, the presence of open burrows within the sediment alters the solute and gas distribution profiles because they expose the previously insulated subsurface pore waters to oxygenated waters. In a novel study, we examined the effects of marine invertebrate burrow architectures on dissolved oxygen diffusion rates in comparison with unburrowed sediment, and through the use of oxygen microsensors, measured O₂ profiles on a micrometer scale around the burrows of several macroinvertebrates. We showed that oxygen diffusive properties were directly related to burrow architecture, and that most burrow types actually facilitated the lateral diffusion of O₂ into previously suboxic/anoxic sediments (Zorn et al., 2006). This, in turn, leads to biogeochemical reactions that might not be predicted from traditional models of ideally zoned sediment. A case in point is the type of cements formed. For instance, in a recent study, we observed a clear relationship between the biogeochemical processes occurring within a burrow microenvironment and the cementation history of the trace fossil Rosselia socialis from shoreface deposits in the Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada (Zorn et al., 2007).

Freshwater sediments are also subject to bioturbation processes that affect the transfer of solutes and gases through the sediment-water interface. Analyses of sediment core from Cooking Lake, Alberta, revealed that H₂S fluctuates from depths of several millimeters during the summer, when cyanobacteria generated sufficient O₂ to drive the oxic-anoxic chemocline into the sediment, but in the winter, the H₂S front extended upwards into the water column due to the cessation of cyanobacterial activity. However, burrowing behaviour was not linked to seasonal changes in the sediment chemistry, which we suggest is due to the ability of Chironomid larvae to exploit oxygen oases in the sediment: in the winter, the larvae harvest their oxygen from the uppermost photosynthetic layer in an otherwise O₂ impoverished sediment. So the burrows are, in part, an oxygen-mining structure (Gingras et al., 2007). Crucially, this behaviour may have influenced the evolution of metazoans in the Neoproterozoic. In a recent paper, we have suggested that perhaps some ancient ichnofossils can be interpreted as oxygen-mining structures, which then could imply that the bottom waters need not have been oxygenated, and the deep seas may have remained anoxic until the latest Neoproterozoic (Gingras et al., in review).

Drs. Murray Gingras and George Pemberton (UofA), along with myself, have initiated a research programme aimed at improving conceptual models for burrow-associated diagenesis. The research will address two important diagenetic manifestations: dolomitization and patchy silica cementation in clastic sediments. The former is seen to be a direct manifestation of the presence of discrete biogenic sedimentary structures and the latter is more commonly associated with cryptic bioturbation. The research will be novel as it will consider both the biogeochemical and mechanical aspects of strongly heterogeneous fabrics. New diagenetic perspectives will be coupled to petrological data with the intention of addressing the following simple objectives: (1) determine the predictability of burrow-influenced cementation and identify the key factors that influence that predictability; (2) present models for upscaling core-scale permeability fabrics to the bed-set scale, and; (3) use the detailed data gathered to model bulk flow and capillary behaviour for idealized burrow facies. We have funding for two students, one being a PhD student, Larry Amskold, and the other at the MSc level, John Gordon.
 

6. Neoproterozoic BIF and Glaciations
 
 

Recent Publications

Moncaster, S.J., Bottrell, S.H., Tellam, J.H., Lloyd, J.W., and Konhauser, K.O., 2000. Migration and attenuation of agrochemical pollutants: Insights from isotopic analysis of groundwater sulphate. Journal of Contaminant Hydrology, 43:147-163.

Phoenix, V.R., Adams, D.G., and Konhauser, K.O., 2000. Cell viability during hydrothermal biomineralisation. Chemical Geology, 169:329-338.

Konhauser, K.O., Phoenix, V.R., Bottrell, S.H., Adams, D.G., and Head, I.M., 2001. Microbial-silica interactions in modern hot spring sinter: Possible analogues for Precambrian siliceous stromatolites. Sedimentology, 48:415-433.

Phoenix, V.R., Konhauser, K.O., Adams, D.G., and Bottrell, S.H., 2001. The role of biomineralization as an ultraviolet shield: Implications for the Archean. Geology, 29:823-826.

Konhauser, K.O., Phoenix, V.R., and Benning, L.G., 2001. How do microorganisms silicify? In: Conference Proceedings of the 10^th International Symposium on Water-Rock Interactions, Cagliari, Sardinia, Italy, 10:1449-1452.

Konhauser, K.O., Mortimer, R.J.G., Morris, K., and Dunn, V., 2002. The role of microorganisms during sediment diagenesis: Implications for radionuclide mobility. In: F. Livens and Keith-Roach, M. (Editors), Microbiology and Radioactivity, pp. 61-100.

Benning, L.G., Phoenix, V., Yee, N., Tobin, M.G., Konhauser, K.O., and Mountain, B.W., 2002. Molecular characterization of cyanobacterial cells during silicification: A synchrotron-based infrared study. In: Geochemistry of the Earth's Surface, pp. 259-263.

Phoenix, V.R., Martinez R.E., Konhauser, K.O., and Ferris F.G., 2002. Characterization and implications of the cell surface reactivity of Calothrix sp. strain KC97. Applied and Environmental Microbiology, 68: 4827-4834.

Konhauser, K.O., Hamade, T., Morris, R.C., Ferris, F.G., Southam, G., Raiswell, R., and Canfield, D., 2002. Could bacteria have formed the Precambrian banded iron formations? Geology, 30:1079-1082.

Konhauser, K.O., Schiffman, P., Fisher, Q.J., 2002. Microbial mediation of authigenic clays during hydrothermal alteration of basaltic tephra, Kilauea Volcano. Geochemistry, Geophysics, and Geosystems, 3: December 17 (2002GC000317).

Hamade, T., Konhauser, K.O., Raiswell, R., Morris, R.C., and Goldsmith, S., 2003. Using Ge:Si ratios to decouple iron and silica fluxes in Precambrian banded iron formations. Geology, 31:35-38.

Yee, N., Phoenix, V.R., Konhauser, K.O. , and Benning, L.G., 2003. The effect of bacteria on SiO₂ precipitation at neutral pH: Implications for bacterial silicification in geothermal hot springs. Chemical Geology, 199:83-90.

Phoenix, V.R., Konhauser, K.O., and Ferris, F.G., 2003. Experimental study of iron and silica immobilization by bacteria in mixed Fe-Si systems: Implications for microbial silicification in hot-springs. Canadian Journal of Earth Sciences, 40:1669-1678.

Konhauser, K.O., Jones, B., Reysenbach, A.-L., and Renaut, R.W., 2003. Hot spring sinters: Keys to understanding Earth’s earliest life forms. Canadian Journal of Earth Sciences, 40:1713-1724.

Benning, L.G., Phoenix, V., Yee, N., and Konhauser, K.O., 2004. The dynamics of cyanobacterial silicification: An infrared micro-spectroscopic investigation. Geochimica et Cosmochimica Acta, 68:743-757.

Konhauser, K.O., 2004. The role of bacteria in banded iron formations. In: Conference Proceedings of the 11th International Symposium on Water-Rock Interactions, Saratoga Springs, New York.

Jones, B., Konhauser, K.O., Renaut, R., and Wheeler, R., 2004. Microbe silicification in Iodine Pool, Waimangu geothermal area, North Island, New Zealand: Implications for recognition and identification of ancient silicified microbes, Journal of the Geological Society of London, 161:983-993.

Konhauser, K.O., Jones, B., Phoenix, V.R., Ferris, G., and Renaut, R.W., 2004. The microbial role in hot spring silicification. Ambio, 33:552-558.

Lalonde, S.V., Konhauser, K.O., Reysenbach, A.-L., and Ferris, F.G., 2005. Thermophilic silicification: The role of Aquificales in hot spring sinter formation. Geobiology, 3:41-52.

Jones, B., Renaut, R., and Konhauser, K.O., 2005. Genesis of large siliceous stromatolites at Frying Pan Lake, Waimangu geothermal field, North Island, New Zealand. Sedimentology, 52:1229-1252.

Reysenbach, A.-L., Banta, A., Civello, S., Daly, J., Mitchel, K., Lalonde, S., Konhauser, K., Rustenholtz, K., and Takacs-Vesbach, C., 2005. The Aquificales in Yellowstone National Park, In: Inskeep, W.P. and T.R. McDermott (Editors), Geothermal Biology and Geochemistry in Yellowstone National Park. Montana State University, Bozeman.

Kappler, A., Pasquero, C., Konhauser, K.O., and Newman, D.K., 2005. Deposition of banded iron formations by phototrophic Fe(II)-oxidizing bacteria. Geology, 33:865-868.

Konhauser, K.O., Newman, D.K., and Kappler, A., 2005. The potential significance of microbial Fe(III)-reduction during Precambrian banded iron formations. Geobiology, 3:167-177

Zorn, M.E., Lalonde, S.V., Gingras, M.K., Pemberton, S.G., and Konhauser, K.O., 2006. Microscale distribution of oxygen in the burrow walls of seven intertidal invertebrates from Willipa Bay, Washington. Geobiology, 4:137-145.

Hussain, M.F., Ahmad, I., and Konhauser, K.O., 2006. Major ion and heavy metal chemistry of the Pachin River, Itanagar, India – Levels and sources. Indian Journal of Environmental Health, 48:27-34.

Konhauser, K.O. and Gingras, M.K., 2007. Linking geomicrobiology with ichnology in marine sediments. Palaios, 22:339-342.

Gingras, M.K., Lalonde, S., Amskold, L., and Konhauser, K.O. , 2007. Wintering Chironomid mine oxygen. Palaios, 22:433-438.

Konhauser, K.O., Amskold, L., Lalonde, S.V., Posth, N.R., Kappler, A., and Anbar, A., 2007. Decoupling photooxidation from shallow-water BIF deposition. Earth and Planetary Science Letters, 258:87-100.

Konhauser, K.O., Lalonde, S., Amskold, L., and Holland, H.D., 2007. Was there really an Archean phosphate crisis? Science, 315:1234.

Fowle, D.A., Roberts, J., Fortin, D., and Konhauser, K.O. 2007. The Evolution of geomicrobiology: Perspectives from the mineral-bacteria interface. Geobiology, 5:207-210.

Lalonde, S., Amskold, L., McDermott, T., Inskeep, B.P., and Konhauser, K.O., 2007. Chemical reactivity of microbe and mineral surfaces in hydrous ferric oxide depositing hydrothermal springs. Geobiology, 5:219-234.

Lalonde, S., Amskold, L., Warren L.A., and Konhauser, K.O., 2007. Surface chemical reactivity and metal adsorptive properties of natural cyanobacterial mats from an alkaline hot spring, Yellowstone National Park. Chemical Geology, 243:36-52.

Zorn, M.E., Muehlenbachs, K., Gingras, M.K., Konhauser, K.O., Pemberton, S.G., and Evoy, R., 2007. Stable isotopic analysis reveals evidence for groundwater/sediment/animal interactions in a marginal marine setting. Palaios, 22:546-553.

Bazylinski, D.A., Frankel, R.B., and Konhauser, K.O., 2007. Modes of biomineralization of magnetite by microbes. Geomicrobiology Journal, 24:465-475.

Pecoits, E., Gingras, M.K., Aubet, N., and Konhauser, K.O., 2008. Ediacaran in Uruguay: Palaeoclimatic and palaeobiologic implications. Sedimentology, 55:689-719

Lalonde, S.V., Smith, D.S., Owttrim G.W., and Konhauser, K.O., 2008(a) Acid-base properties of cyanobacterial surfaces I: influences of growth phase and nitrogen metabolism on surface reactivity. Geochimica et Cosmochimica Acta, 72:1257-1268.

Lalonde, S.V., Smith, D.S., Owttrim G.W., and Konhauser, K.O., 2008(b) Acid-base properties of cyanobacterial surfaces II: Silica as a chemical stressor influencing cell surface reactivity. Geochimica et Cosmochimica Acta, 72:1269-1280.

Hobbs, W.O., Wolfe, A.P., Inskeep, W.P., Amskold, L., and Konhauser, K.O., 2008. Epipelic diatom community from an extreme environment: Beowulf Spring, Yellowstone National Park, U.S.A. Nova Hedwigia (Special Issue dedicated to Eugene Stoermer), in press.

Posth, N.R., Konhauser, K.O., and Kappler, A., 2008. Microbiological processes in BIF deposition. In: C. Glenn and I. Jarvis (Editors), Authigenic Minerals: Sedimentology, Geochemistry, Origins, Distribution and Applications. IAS Special Publication Series, in press.

Konhauser, K.O., Lalonde, S.V., and Phoenix, V.R., 2008. Bacterial biomineralization: Where to from here? Geobiology, 6:298-302.

Phoenix, V.R. and Konhauser, K.O., 2008. Benefits of bacterial biomineralization. Geobiology, 6:303-308.

Newman, D.K., Konhauser, K.O. and Reysenbach, A.-L., 2008. A tribute to Terry Beveridge: Pioneer in the field of Geomicrobiology. Geobiology, 6:189.

Posth, N., Hegler, F., Konhauser, K.O., and Kappler, A., 2008. Ocean temperature fluctuations as trigger for Precambrian Si and Fe deposition. Nature Geoscience, 1:703-707.

Pecoits, E., Gingras, M.K., and Konhauser, K.O., 2009. Las Ventanas and San Carlos formations, Maldonado Group, Uruguay. Journal of the Geological Society of London, accepted, in press.

Konhauser, K.O., 2009. Bacterial Clay Authigenesis. In: J. Reitner and V. Thiel (Editors), Encyclopedia of Geobiology. Springer, Berlin, in press.

Fowle, D.A. and Konhauser, K.O., 2009. Microbial Surface Reactivity. In: J. Reitner and V. Thiel (Editors), Encyclopedia of Geobiology. Springer, Berlin, in press.

Posth, N.R., Konhauser, K.O., and Kappler, A., 2009. Banded Iron Formations. In: J. Reitner and V. Thiel (Editors), Encyclopedia of Geobiology. Springer, Berlin, in press.

Konhauser, K.O. , Gingras, M.K., and Kappler, A., 2009. Diagenesis – Biologically Controlled. In: J. Reitner and V. Thiel (Editors), Encyclopedia of Geobiology. Springer, Berlin, in press.

Geomicrobiology Research Group

Stefan Lalonde - PhD student
email - stefanw@ualberta.ca
web page

Daniel Petrash - MSc student
email - petrash@ualberta.ca