Scholarly Work - Center for Biofilm Engineering

Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/9335

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    Dissimilatory iron-reducing bacteria can influence the reduction of carbon tetrachloride by iron metal
    (2000-06) Gerlach, Robin; Cunningham, Alfred B.; Caccavo, Frank
    Little is known about the long-term performance of zerovalent iron (Fe0) subsurface barriers. Groundwater exposure includes corrosion processes that can passivate the Fe0 surface and decrease barrier reaction rates. We present evidence that dissimilatory iron-reducing bacteria (DIRB) can stimulate the rate of carbon tetrachloride (CT) transformation in the presence of corroded iron. The DIRB, Shewanella alga BrY, adhered to the corroded Fe surfaces that showed little or no capacity to transform CT. The addition of BrY to these systems with decreased CT transformation rates resulted in increased ferrous iron concentrations and increased CT transformation to chloroform (CF). The results suggest that DIRB can have an influence on the long-term performance of Fe0 barriers.
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    Biogeochemical elimination of chromium (VI) contaminated water
    (2002-01) Nyman, Jennifer L.; Caccavo, Frank; Cunningham, Alfred B.; Gerlach, Robin
    Ferrous iron [Fe(II)] reductively transforms heavy metals in contaminated groundwater, and the bacterial reduction of indigenous ferric iron [Fe(II)] has been proposed as a means of establishing redox reactive barriers in the subsurface. The reduction of Fe(III) to Fe(II) can be accomplished by stimulation of microbially produced Fe(II) can chemically react with contaminants such as Cr(VI) to form insoluble Cr(III) precipitates. The DMRB Shewanella algae BrY reduced highly soluble Cr(VI) to insoluble Cr(III). Once the chemical Cr(VI) reduction capacity of the Fe(II)/Fe(III) couple in the experimental systems was exhausted, the addition of S. algae BrY allowed for the repeated reduction of Fe(III) to Fe(II), which again reduced Cr(VI) to Cr(III). The research presented herein indicates that a biological process using DMRB allows the establishment of biogeochemical cycle that facilitates chromium production. Such a system could provide a means for establishing and maintaining remedial redox reactive zones on Fe(III)- bearing subsurface environments.
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    Anomalous fluid transport in porous media induced by biofilm growth
    (2004-11) Seymour, Joseph D.; Gage, Justin P.; Codd, Sarah L.; Gerlach, Robin
    Magnetic resonance measurements of the transition from normal to anomalous hydrodynamic dispersion in porous media due to biological activity are presented. Fractional advection-diffusion equations are shown to provide models for the measured impact of biofilm growth on porous media transport dynamics.
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    Biofilms in porous media
    (2000) Bouwer, Edward J.; Rijnaarts, Huub H. M.; Cunningham, Alfred B.; Gerlach, Robin
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    Use of reversed-phase high-performance liquid chromatography-diode array detection for complete separation of 2,4,6-trinitrotoluene metabolites and EPA Method 8330 explosives: Influence of temperature and an ion-pair reagent
    (2004-01) Borch, Thomas; Gerlach, Robin
    Explosives such as 2,4,6-trinitrotoluene (TNT), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are widely distributed environmental contaminants. Complete chromatographic separation is necessary in order to accurately determine and quantify explosives and their degradation products in environmental samples and in (bio)transformation studies. The present study describes a RP-HPLC method with diode array detection using a LC-8 guard column, a Supelcosil LC-8 chromatographic column, and a gradient elution system. This gradient method is capable of baseline separating the most commonly observed explosives and TNT transformation metabolites including 2,4,6-triaminotoluene (TAT) in a single run. The TNT metabolites separated were 2-hydroxylamino-4,6-dinitrotoluene, 4-hydroxylamino-2,6-dinitrotoluene, 2,4-dihydroxylamino-6-nitrotoluene, 4,4',6,6'-tetranitro-2,2'-azoxytoluene, 2,2',6,6'-tetranitro-4,4'-azoxytoluene, 4,4',6,6'-tetranitro-2,2'-azotoluene, 2,2',6,6'-tetranitro-4,4'-azotoluene, 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,6-diamino-4-nitrotoluene, 2,4-diamino-6-nitrotoluene, and TAT. The same gradient method at a different column temperature can also be used to baseline separate the explosives targeted in the Environmental Protection Agency (EPA) Method 8330 with approximately 22% reduction in total run time and 48% decrease in solvent consumption compared to previously published methods. Good separation was also obtained when all TNT metabolites and EPA Method 8330 compounds (a total of 23 compounds) were analyzed together; only 2,6-DANT and HMX co-eluted in this case. The influence of temperature (35B55 C) and the use of an ion-pair reagent on the chromatographic resolution and retention were investigated. Temperature was identified as the key parameter for optimal baseline separation. Increased temperature resulted in shorter retention times and better peak resolution especially for the aminoaromatics investigated. The use of an ion-pair reagent (octanesulfonic acid) generally resulted in longer retention times for compounds containing amine functional groups, more baseline noise, and decreased peak resolution.
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    Impact of ferrihydrite and anthraquinone-2,6-disulfonate on the reductive transformation of 2,4,6-trinitrotoluene by a gram-positive fermenting bacterium
    (2005-09) Borch, Thomas; Inskeep, William P.; Harwood, Jace A.; Gerlach, Robin
    Batch studies were conducted to explore differences in the transformation pathways of 2,4,6-trinitrotoluene (TNT) reduction by a Gram-positive fermenting bacterium (Cellulomonas sp. strain ES6) in the presence and absence of ferrihydrite and the electron shuttle anthraquinone-2,6-disulfonate (AQDS). Strain ES6 was capable of TNT and ferrihydrite reduction with increased reduction rates in the presence of AQDS. Hydroxylaminodinitrotoluenes, 2,4-dihydroxylamino-6-nitrotoluene (2,4-DHANT), and tetranitroazoxytoluenes were the major metabolites observed in ferrihydrite- and AQDS-free systems in the presence of pure cell cultures. Ferrihydrite enhanced the production of amino derivatives because of reactions with microbially produced surface-associated Fe(II). The presence of AQDS in the absence of ferrihydrite promoted the fast initial formation of arylhydroxylamines such as 2,4-DHANT. However, unlike in pure cell systems, these arylhydroxylamines were transformed into several unidentified polar products. When both microbially reduced ferrihydrite and AQDS were present simultaneously, the reduction of TNT was more rapid and complete via pathways that would have been difficult to infer solely from single component studies. This study demonstrates the complexity of TNT degradation patterns in model systems where the interactions among bacteria, Fe minerals, and organic matter have a pronounced effect on the degradation pathway of TNT.
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    Visualization and characterization of dynamic patterns of flow, growth, and activity of biofilms growing in porous media
    (2005) Sharp, Robert R.; Stoodley, Paul; Adgie, M.; Gerlach, Robin; Cunningham, Alfred B.
    Using a mesoscale porous media flat plate reactor we utilized a naturally bioluminescent biofilm (V. fischeri) and dye studies to obtain valuable information on the interactions between biofilms and reactive flow in porous media. The growth and development of the V. fischeri biofilm in a porous media geometry was studied using digital time lapse images of the bioluminescent signal given off by the developing biofilm. The effect of biofilm development on porous media hydrodynamics was examined using dye tracer studies and image analysis. The natural bioluminescence of the V. fischeri allowed real-time, in-situ study of biofilm development in porous media, without destruction of the biofilm. Dye studies and image analysis enabled the study of effects of biofilm accumulation on porous media hydraulics, with comparisons to plug flow and completely mixed systems with varying degrees of biofilm accumulation. The real-time nature of the study permitted us to visualize dynamic flow channel formation within the biofilm/porous media system. In addition, the sensitivity of the V. fischeri biofilm to dissolved oxygen allowed us to capture real-time images of reactive transport within the system. This work is the first meso-scale visualization of the interactions between biofilm and flow in porous media.
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    Magnetic resonance microscopy of biofouling induced scale dependent transport in porous media
    (2007-06) Seymour, Joseph D.; Gage, Justin P.; Codd, Sarah L.; Gerlach, Robin
    Non-invasive magnetic resonance microscopy (MRM) methods are applied to study biofouling of a homogeneous model porous media. MRM of the biofilm biomass using magnetic relaxation weighting shows the heterogeneous nature of the spatial distribution of the biomass as a function of growth. Spatially resolved MRM velocity maps indicate a strong variation in the pore scale velocity as a function of biofilm growth. The hydrodynamic dispersion dynamics for flow through the porous media is quantitatively characterized using a pulsed gradient spin echo technique to measure the propagator of the motion. The propagator indicates a transition in transport dynamics from a Gaussian normal diffusion process following a normal advection diffusion equation to anomalous transport as a function of biofilm growth. Continuous time random walk models resulting in a time fractional advection diffusion equation are shown to model the transition from normal to anomalous transport in the context of a conceptual model for the biofouling. The initially homogeneous porous media is transformed into a more complex heterogeneous porous media by the biofilm growth.
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    Effects of starvation on bacterial transport through porous media
    (2007-06) Cunningham, Alfred B.; Sharp, Robert R.; Caccavo, Frank; Gerlach, Robin
    A major problem preventing widespread implementation of microbial injection strategies for bioremediation and/or microbially enhanced oil recovery is the tendency of bacteria to strongly adhere to surfaces in the immediate vicinity of the injection point. Long term (weeks to months) nutrient starvation of bacteria prior to injection can decrease attachment and enhance transport through porous media. This paper summarizes results of starvation-enhanced transport experiments in sand columns of 30 cm, 3 m, and 16 m in length. The 16 m column experiments compared transport, breakthrough and distribution of adhered cells for starved and vegetative cultures of Klebsiella oxytoca, a copious biofilm producer. Results from these experiments were subsequently used to design and construct a field-scale biofilm barrier using starved Pseudomonas fluorescens. The 30 cm and 3 m sand columns experiments investigated starvation-enhanced transport of Shewanella algae BrY, a dissimilatory metal-reducing bacterium. In both cases the vegetative cells adsorbed onto the sand in higher numbers than the starved cells, especially near the entrance of the column. These results, taken together with studies cited in the literature, indicate that starved cells penetrate farther (i.e. higher breakthrough concentration) and adsorb more uniformly along the flow path than vegetative cells.
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    Production of eight different hydride complexes and nitrite release from 2,4,6-trinitrotoluene by Yarrowia lipolytica
    (2007-10) Ziganshin, Ayrat M.; Gerlach, Robin; Borch, Thomas; Naumov, A. V.; Naumova, R. P.
    2,4,6-Trinitrotoluene (TNT) transformation by the yeast strain Yarrowia lipolytica AN-L15 was shown to occur via two different pathways. Direct aromatic ring reduction was the predominant mechanism of TNT transformation, while nitro group reduction was observed to be a minor pathway. Although growth of Y.lipolytica AN-L15 was inhibited initially in the presence of TNT, TNT transformation was observed, indicating that the enzymes necessary for TNT reduction were present initially. Aromatic ring reduction resulted in the transient accumulation of eight different TNT-hydride complexes, which were characterized using high performance liquid chromatography, UV-visible diode array detection, and negative-mode atmospheric pressure chemical ionization mass spectrometry (APCI-MS). APCI-MS analysis revealed three different groups of TNT-hydride complexes with molecular ions at m/z 227, 228, and 230, which correspond to TNT-mono- and dihydride complexes and protonated dihydride isomers, respectively. One of the three protonated dihydride complex isomers detected appears to release nitrite in the presence of strain AN-L15. This release of nitrite is of particular interest since it can provide a pathway towards complete degradation and detoxification of TNT.
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