Scholarly Work - Center for Biofilm Engineering
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/9335
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Item Kinetics of Calcite Precipitation by Ureolytic Bacteria under Aerobic and Anaerobic Conditions(2019-05) Mitchell, Andrew C.; Espinosa-Ortiz, Erika J.; Parks, Stacy L.; Phillips, Adrienne J.; Cunningham, Alfred B.; Gerlach, RobinThe kinetics of urea hydrolysis (ureolysis) and induced calcium carbonate (CaCO3) precipitation for engineering use in the subsurface was investigated under aerobic conditions using Sporosarcina pasteurii (ATCC strain 11859) as well as Bacillus sphaericus strains 21776 and 21787. All bacterial strains showed ureolytic activity inducing CaCO3 precipitation aerobically. Rate constants not normalized to biomass demonstrated slightly higher-rate coefficients for both ureolysis (kurea) and CaCO3 precipitation (kprecip) for B. sphaericus 21776 (kurea=0.10±0.03 h−1, kprecip=0.60±0.34 h−1) compared to S. pasteurii (kurea=0.07±0.02 h−1, kprecip=0.25±0.02 h−1), though these differences were not statistically significantly different. B. sphaericus 21787 showed little ureolytic activity but was still capable of inducing some CaCO3 precipitation. Cell growth appeared to be inhibited during the period of CaCO3 precipitation. Transmission electron microscopy (TEM) images suggest this is due to the encasement of cells and was reflected in lower kurea values observed in the presence of dissolved Ca. However, biomass regrowth could be observed after CaCO3 precipitation ceased, which suggests that ureolysis-induced CaCO3 precipitation is not necessarily lethal for the entire population. The kinetics of ureolysis and CaCO3 precipitation with S. pasteurii was further analyzed under anaerobic conditions. Rate coefficients obtained in anaerobic environments were comparable to those under aerobic conditions; however, no cell growth was observed under anaerobic conditions with NO−3, SO2−4 or Fe3+ as potential terminal electron acceptors. These data suggest that the initial rates of ureolysis and ureolysis-induced CaCO3 precipitation are not significantly affected by the absence of oxygen but that long-term ureolytic activity might require the addition of suitable electron acceptors. Variations in the ureolytic capabilities and associated rates of CaCO3 precipitation between strains must be fully considered in subsurface engineering strategies that utilize microbial amendments.Item Effect of selenite on the morphology and respiratory activity of Phanerochaete chrysosporium biofilms(2016-06) Espinosa-Ortiz, Erika J.; Pechaud, Yoan; Lauchnor, Ellen G.; Eldon, Rene R.; Gerlach, Robin; Peyton, Brent M.; van Hullebusch, Eric D.; Lens, Piet N. L.The temporal and spatial effects of selenite (SeO32-) on the physical properties and respiratory activity of Phanerochaete chrysosporium biofilms, grown in flow-cell reactors, were investigated using oxygen microsensors and confocal laser scanning microscopy (CLSM) imaging. Exposure of the biofilm to a SeO32- load of 1.67 mg Se L-1 h-1 (10 mg Se L-1 influent concentration), for 24 h, resulted in a 20% reduction of the O2 flux, followed by a ~10% decrease in the glucose consumption rate. Long-term exposure (4 days) to SeO32- influenced the architecture of the biofilm by creating a more compact and dense hyphal arrangement resulting in a decrease of biofilm thickness compared to fungal biofilms grown without SeO32-. To the best of our knowledge, this is the first time that the effect of SeO32- on the aerobic respiratory activity on fungal biofilms is described.