Analysis of bacterial cell properties and transport in porous media
Environmental Biocolloid Engineering Laboratory, Seoul National University, Seoul, Korea.Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering (Impact Factor: 1.16). 05/2010; 45(6):682-91. DOI: 10.1080/10934521003648867
The cell properties of Escherichia coli ATCC 11105 (gram-negative rod and motile) and Staphylococcus aureus ATCC 10537 (gram-positive coccus and immotile) and their transport in porous media were investigated in this study. Bacterial cell properties such as cell geometry, zeta potential, and hydrophobicity were analyzed using surface measurement and bio-imaging techniques. Transport of both bacteria was examined using column experiments in quartz sand, iron-coated sand (ICS), iron-coated sand pretreated with humic acid (ICS-HA), glass bead, and field soil (sandy loam). Experimental results revealed that E. coli had a larger equivalent diameter and were more hydrophobic than S. aureus, while the difference in zeta potential was not statistically significant even though E. coli had a slightly more negative value than S. aureus. Column experimental results demonstrated that the mass recovery of S. aureus was higher than that of E. coli in all porous media used in this study. These results indicate that transport of S. aureus was greater than E. coli under the given experimental conditions. This study demonstrates that pathogenic bacteria with different characteristics from E. coli can have different transport in porous media.
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ABSTRACT: Bacterial cells that enter the groundwater system commonly experience desiccation stresses (i.e., bacterial cells are directly exposed to air) when traveling through the unsaturated layer of soil. Little is known about the effects of desiccation on the transport of bacterial cells in the groundwater system. In this research, we investigated the transport of desiccated and non-desiccated Escherichia coli K12 (ATCC 10798) cells through saturated sand packs using laboratory column transport experiments. Cell desiccation was performed at 25°C under relative humidity (RH) levels of 22%, 53%, 75%, and 97%, respectively, and the desiccation duration was 22 h. Our results showed that desiccation reduced the viability of E. coli cells under all RH levels and increased the transport of E. coli cells under ≥75% RH levels. The increase in the transport of the desiccated E. coli cells was not related to changes in cell size or cell zeta potential. Desiccation under high (i.e., ≥75%) RH levels, however, led to lower cell hydrophobicity, which was found to be positively correlated with cell transport.
Conference Paper: On shared Medium Architecture with Output Buffer Constraints
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ABSTRACT: The purpose of this study was to determine the association between cardiac compression and exercise impairment in patients with a large hiatal hernia (HH). Dyspnea and exercise impairment are common symptoms of a large HH with unknown pathophysiology. Studies evaluating the contribution of cardiac compression to the pathogenesis of these symptoms have not been performed. We collected clinical data from a consecutive series of 30 patients prospectively evaluated with resting and stress echocardiography, cardiac computed tomography, and respiratory function testing before and after laparoscopic HH repair. Left atrial (LA), inferior pulmonary vein, and coronary sinus compression was analyzed in relation to exercise capacity (metabolic equivalents [METs] achieved on Bruce treadmill protocol). Exertional dyspnea was present in 25 of 30 patients (83%) despite normal mean baseline respiratory function. Moderate to severe LA compression was qualitatively present in 23 of 30 patients (77%) on computed tomography. Right and left inferior pulmonary vein and coronary sinus compression was present in 11 of 30 (37%), 12 of 30 (40%), and 26 of 30 (87%) patients, respectively. Post-operatively, New York Heart Association functional class and exercise capacity improved significantly (number of patients in New York Heart Association functional classes I, II, III, and IV: 6, 11, 11, and 2 vs. 26, 4, 0, and 0, respectively, p < 0.001; METs [percentage predicted]: 75 ± 24% vs. 112 ± 23%, p < 0.001) and resolution of cardiac compression was observed. Absolute change in LA diameter on the echocardiogram was the only independent cardiorespiratory predictor of exercise capacity improvement post-operatively (p = 0.006). We demonstrate, for the first time, marked exercise impairment and cardiac compression in patients with a large HH and normal respiratory function. After HH repair, exercise capacity improves significantly and correlates with resolution of LA compression.
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