Center for Biofilm Engineering (CBE)
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At the Center for Biofilm Engineering (CBE), multidisciplinary research teams develop beneficial uses for microbial biofilms and find solutions to industrially relevant biofilm problems. The CBE was established at Montana State University, Bozeman, in 1990 as a National Science Foundation Engineering Research Center. As part of the MSU College of Engineering, the CBE gives students a chance to get a head start on their careers by working on research teams led by world-recognized leaders in the biofilm field.
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Item Polar organic solvent removal in a microcosm constructed wetlands(2005-10) Kowles-Grove, J. L.; Stein, Otto R.Three polar organic solvents, acetone, tetrahydrofuran (THF) and 1-butanol, were added at 100 mg/l each to post-primary municipal wastewater in order to simulate a mixed waste stream. This mixture was applied to an experimental microcosm subsurface constructed wetland system consisting of replicates of Juncus effusus, Carex lurida, Iris pseudacorus, Pondeteria cordata and unplanted controls in a series of 14-day batch incubations over a yearlong period simulating a summer and winter season. 90% removal of 1-butanol typically took less than 3 days. 90% removal of acetone required from 5 to 10 days in summer and 10 to 14 days in winter. 90% removal of THF required at least 10 days and was frequently not achieved during the 14-day incubations. Initial experiments confirmed that the majority of solvent removal was via microbial bioremediation. Solvent removal was typically better in planted replicates, especially Juncus, regardless of season. The removal rate of all solvents was slower in winter, but the seasonal effect was most pronounced in the unplanted control replicates and least in the Carex and Juncus replicates. Plant and seasonal effects are believed to be due, in part, to variation in metabolic pathways induced by plant and seasonal variation in available root-zone oxygen. Variation in transpiration also influenced species and seasonal effects on THF removal, but not the other more biodegradable solvents. A model based on a prediction of plant uptake of nonionic dissolved chemicals suggests that as much as 39% of the THF in solution could have been removed through plant transpiration.Item Detecting Microbially Induced Calcite Precipitation in a Model Well-Bore Using Downhole Low-Field NMR(2017-02) Kirkland, Catherine M.; Zanetti, Sam; Grunewald, Elliot; Walsh, David O.; Codd, Sarah L.; Phillips, Adrienne J.Microbially induced calcite precipitation (MICP) has been widely researched recently due to its relevance for subsurface engineering applications including sealing leakage pathways and permeability modification. These applications of MICP are inherently difficult to monitor nondestructively in time and space. Nuclear magnetic resonance (NMR) can characterize the pore size distributions, porosity, and permeability of subsurface formations. This investigation used a low-field NMR well-logging probe to monitor MICP in a sand-filled bioreactor, measuring NMR signal amplitude and T2 relaxation over an 8 day experimental period. Following inoculation with the ureolytic bacteria, Sporosarcina pasteurii, and pulsed injections of urea and calcium substrate, the NMR measured water content in the reactor decreased to 76% of its initial value. T2 relaxation distributions bifurcated from a single mode centered about approximately 650 ms into a fast decaying population (T2 less than 10 ms) and a larger population with T2 greater than 1000 ms. The combination of changes in pore volume and surface minerology accounts for the changes in the T2 distributions. Destructive sampling confirmed final porosity was approximately 88% of the original value. These results indicate the low-field NMR well-logging probe is sensitive to the physical and chemical changes caused by MICP in a laboratory bioreactor.Item Investigating the influence of the initial biomass distribution and injection strategies on biofilm-mediated calcite precipitation in porous media(2016-09) Hommel, Johannes; Lauchnor, Ellen G.; Gerlach, Robin; Cunningham, Alfred B.; Ebigbo, Anozie; Helmig, Rainer; Class, HolgerAttachment of bacteria in porous media is a complex mixture of processes resulting in the transfer and immobilization of suspended cells onto a solid surface within the porous medium. Quantifying the rate of attachment is difficult due to the many simultaneous processes possibly involved in attachment, including straining, sorption, and sedimentation, and the difficulties in measuring metabolically active cells attached to porous media. Preliminary experiments confirmed the difficulty associated with measuring active Sporosarcina pasteurii cells attached to porous media. However, attachment is a key process in applications of biofilm-mediated reactions in the subsurface such as microbially induced calcite precipitation. Independent of the exact processes involved, attachment determines both the distribution and the initial amount of attached biomass and as such the initial reaction rate. As direct experimental investigations are difficult, this study is limited to a numerical investigation of the effect of various initial biomass distributions and initial amounts of attached biomass. This is performed for various injection strategies, changing the injection rate as well as alternating between continuous and pulsed injections. The results of this study indicate that, for the selected scenarios, both the initial amount and the distribution of attached biomass have minor influence on the Ca2+2+ precipitation efficiency as well as the distribution of the precipitates compared to the influence of the injection strategy. The influence of the initial biomass distribution on the resulting final distribution of the precipitated calcite is limited, except for the continuous injection at intermediate injection rate. But even for this injection strategy, the Ca2+2+ precipitation efficiency shows no significant dependence on the initial biomass distribution.Item Gel-Entrapped Staphylococcus aureus Bacteria as Models of Biofilm Infection Exhibit Growth in Dense Aggregates Oxygen Limitation, Antibiotic Tolerance, and Heterogeneous Gene Expression(2016-08) Pabst, Breana; Pitts, Betsey; Lauchnor, Ellen G.; Stewart, Philip S.An experimental model that mimicked the structure and characteristics of in vivo biofilm infections, such as those occurring in the lung or in dermal wounds where no biomaterial surface is present, was developed. In these infections, microbial biofilm forms as cell aggregates interspersed in a layer of mucus or host matrix material. This structure was modeled by filling glass capillary tubes with an agarose gel that had been seeded with Staphylococcus aureus bacteria and then incubating the gel biofilm in medium for up to 30 h. Confocal microscopy showed that the bacteria formed in discrete pockets distributed throughout the gel matrix. These aggregates enlarged over time and also developed a size gradient, with the clusters being larger near the nutrient- and oxygen-supplied interface and smaller at greater depths. Bacteria entrapped in gels for 24 h grew slowly (specific growth rate, 0.06 h−1) and were much less susceptible to oxacillin, minocycline, or ciprofloxacin than planktonic cells. Microelectrode measurements showed that the oxygen concentration decreased with depth into the gel biofilm, falling to values less than 3% of air saturation at depths of 500 μm. An anaerobiosis-responsive green fluorescent protein reporter gene for lactate dehydrogenase was induced in the region of the gel where the measured oxygen concentrations were low, confirming biologically relevant hypoxia. These results show that the gel biofilm model captures key features of biofilm infection in mucus or compromised tissue: formation of dense, distinct aggregates, reduced specific growth rates, local hypoxia, and antibiotic tolerance.Item Escherichia coli O157:H7 attachment and persistence within root biofilm of common treatment wetlands plants(2017-01) VanKempen-Fryling, Rachel J.; Camper, Anne K.Pathogen retention and subsequent release within the rhizosphere of wastewater treatment wetlands may be a concern for human health. To address this concern, the enteric pathogen Escherichia coli O157:H7 with a DsRed plasmid insertion was used as a model pathogenic organism in an open-air chemostat reactor with constant flow of simulated wastewater. Colonization and persistence of the organism was tracked on roots of two obligate wetland plant species, Carex utriculata and Schoenoplectus acutus, originally grown in pilot scale wetland reactors. Teflon nylon string, clean and with existing indigenous biofilm, was used as an inert surface control. Epifluorescence microscopy and qPCR were used to verify E. coli O157:H7 abundance for up to 1 week. Initial attachment was seen on all surfaces, with colonization decreasing through 1 week. qPCR showed preferential association of the pathogen with roots over the nylon. There was a significant difference between plant type; S. acutus showed significantly higher numbers compared to C. utriculata. E. coli O157:H7 binding and persistence on root surfaces may be a means of survival in treatment wetlands.Item Influence of pH on 2,4,6-trinitrotoluene degradation by Yarrowia lipolytica(2010-04) Ziganshin, Ayrat M.; Naumova, R. P.; Pannier, Andy J.; Gerlach, RobinThe microbial reduction of the aromatic ring of 2,4,6-trinitrotoluene (TNT) can lead to its complete destruction. The acid-tolerant yeast Yarrowia lipolytica AN-L15 transformed TNT through hydride ion-mediated reduction of the aromatic ring (as the main pathway), resulting in the accumulation of nitrite and nitrate ions, as well as through nitro group reduction (as minor pathway), resulting in hydroxylamino- and aminoaromatics. TNT transformation depended on the yeasts' ability to acidify the culture medium through the production of organic acids. Aeration and a low medium buffer capacity favored yeast growth and resulted in rapid acidification of the medium, which influenced the rate and extent of TNT transformation. This is the first time that nitrate has been detected as a major product of microbial TNT degradation, and this work demonstrates the importance of pH on TNT biotransformation. The ability of Y. lipolytica AN-L15 to reduce the TNT aromatic ring to form TNT-hydride complexes, followed by their denitration, makes this strain a potential candidate for bioremediation of sites contaminated with explosives. (c) 2010 Elsevier Ltd. All rights reserved.Item Application of molecular techniques to elucidate the influence of cellulosic waste on the bacterial community structure at a simulated low level waste site(2010-03) Field, E. K.; D'Imperio, Seth; Miller, A. R.; VanEngelen, Michael R.; Gerlach, Robin; Lee, Brady D.; Apel, William A.; Peyton, Brent M.Low-level radioactive waste sites, including those at various U.S. Department of Energy (DOE) sites, frequently contain cellulosic waste in the form of paper towels, cardboard boxes, or wood contaminated with heavy metals and radionuclides such as chromium and uranium. To understand how the soil microbial community is influenced by the presence of cellulosic waste products, multiple soil samples were obtained from a non-radioactive model low-level waste test pit at the Idaho National Laboratory. Samples were analyzed using 16S rRNA gene clone libraries and 16S rRNA gene microarray (PhyloChip) analyses. Both methods revealed changes in the bacterial community structure with depth. In all samples, the PhyloChip detected significantly more Operational Taxonomic Units (OTUs), and therefore relative diversity, than the clone libraries. Diversity indices suggest that diversity is lowest in the Fill (F) and Fill Waste (FW) layers and greater in the Wood Waste (WW) and Waste Clay (WC) layers. Principal coordinates analysis and lineage specific analysis determined that Bacteroidetes and Actinobacteria phyla account for most of the significant differences observed between the layers. The decreased diversity in the FW layer and increased members of families containing known cellulose degrading microorganisms suggests the FW layer is an enrichment environment for these organisms. These results suggest that the presence of the cellulosic material significantly influences the bacterial community structure in a stratified soil system.Item Assessing biofouling on polyamide reverse osmosis (RO) membrane surfaces in a laboratory system(2010-04) Khan, Mohiuddin M. T.; Stewart, Philip S.; Moll, D. J.; Mickols, W. E.; Burr, Mark D.; Nelson, Sara E.; Camper, Anne K.Biofouling of reverse osmosis (RO) membranes is a major impediment in both wastewater reuse and desalination of sea/brackish waters. A benefit to the industry would be a simple screening approach to evaluate biofouling resistant RO membranes for their propensity to biofoulants. To observe the relationship between initial membrane productivity and control of biofilm formation governed by surface modification to the aromatic polyamide thin-film composite RO membranes, three different RO membranes developed by the FilmTec Corporation including FilmTec’s commercial membrane BW30 (RO#1) and two experimental membranes (RO #2 and #3) were used. RO #2 and RO #3 were modified with a proprietary aliphatic group and with an extra proprietary aromatic group, respectively. Membrane swatches were fixed on coupons in rotating disk reactor systems without filtration and exposed to water with indigenous organisms supplemented with 1.5 mg/L organic carbon under continuous flow. After biofouling had developed, the membranes were sacrificed and subjected to several analyses. Staining and epifluorescence microscopy revealed more cells on RO #2 and #3 compared to RO #1. Based on image analysis of 5-µmthick stained biofoulant cryo-sections, the accumulation of hydrated biofoulants on RO #1 and #3 were from 0.87 to 1.26µm/day, which was lower than that on RO#2 (2.19µm/day). Biofoulants increased the hydrophobicity of RO #2 to the greatest amount, up to 32°, as determined by contact angle. In addition, a wide range of changes of the chemical elements of the RO surfaces was observed with X-ray photoelectron spectroscopy analysis. RO #2 with the highest initial membrane productivity showed the poorest biofouling resistance. A combination of these novel approaches showed good agreement and suggested that membrane productivity, heterogeneity of anti-biofouling agents on membrane surface, stability of surface chemical elements and the role of virgin RO surface hydrophobicity should be jointly considered during the development of anti-biofouling polyamide thin-film RO surfaces.Item Identification and characterization of a novel member of the radical AdoMet enzyme superfamily and implications for the biosynthesis of the Hmd hydrogenase active site cofactor(2009-11) McGlynn, Shawn E.; Boyd, Eric S.; Shepard, Eric M.; Lange, Rachel K.; Gerlach, Robin; Broderick, Joan B.; Peters, John W.The genetic context, phylogeny, and biochemistry of a gene flanking the H2-forming methylene-H4-methanopterin dehydrogenase gene (hmdA), here designated hmdB, indicate that it is a new member of the radical S-adenosylmethionine enzyme superfamily. In contrast to the characteristic CX3CX2C or CX2CX4C motif defining this family, HmdB contains a unique CX5CX2C motif.Item Microbially enhanced carbon capture and storage by mineral-trapping and solubility-trapping(2010-07) Mitchell, Andrew C.; Dideriksen, K.; Spangler, Lee H.; Cunningham, Alfred B.; Gerlach, RobinThe potential of microorganisms for enhancing carbon capture and storage (CCS) via mineral-trapping (where dissolved CO2 is precipitated in carbonate minerals) and solubility trapping (as dissolved carbonate species in solution) was investigated. The bacterial hydrolysis of urea (ureolysis) was investigated in microcosms including synthetic brine (SB) mimicking a prospective deep subsurface CCS site with variable headspace pressures [p(CO2)] of 13C-CO2. Dissolved Ca2+ in the SB was completely precipitated as calcite during microbially induced hydrolysis of 5-20 g L-1 urea. The incorporation of carbonate ions from 13C-CO2 (13C-CO32-) into calcite increased with increasing p(13CO2) and increasing urea concentrations: from 8.3% of total carbon in CaCO3 at 1 g L-1 to 31% at 5 g L-1, and 37% at 20 g L-1. This demonstrated that ureolysis was effective at precipitating initially gaseous [CO2(g)] originating from the headspace over the brine. Modeling the change in brine chemistry and carbonate precipitation after equilibration with the initial p(CO2) demonstrated that no net precipitation of CO2(g) via mineral-trapping occurred, since urea hydrolysis results in the production of dissolved inorganic carbon. However, the pH increase induced by bacterial ureolysis generated a net flux of CO2(g) into the brine. This reduced the headspace concentration of CO2 by up to 32 mM per 100 mM urea hydrolyzed because the capacity of the brine for carbonate ions was increased, thus enhancing the solubility-trapping capacity of the brine. Together with the previously demonstrated permeability reduction of rock cores at high pressure by microbial biofilms and resilience of biofilms to supercritical CO2, this suggests that engineered biomineralizing biofilms may enhance CCS via solubility-trapping, mineral formation, and CO2(g) leakage reduction.