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- Title
- IN-FRAME MUTAGENESIS OF GENES ENCODING A SELENIUM-DEPENDENT MOLYBDENUM HYDROXYLASE AND PUTATIVE ACCESSORY PROTEINS IN ENTEROCOCCUS FAECALIS.
- Creator
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Mallard, Christopher, Self, William, University of Central Florida
- Abstract / Description
-
Enterococcus faecalis is a well known nosocomial drug resistant pathogen that is responsible for urinary tract infections, bacteremia, wound infections and endocarditis through the formation of biofilms. It has been shown that 68 genes present within the core genome of E. faecalis are upregulated in biofilm formation. One of those 68 genes is a putative selenium-dependent molybdenum hydroxylase (SDMH). Adjacent to this gene are a series of open reading frames that have been postulated to play...
Show moreEnterococcus faecalis is a well known nosocomial drug resistant pathogen that is responsible for urinary tract infections, bacteremia, wound infections and endocarditis through the formation of biofilms. It has been shown that 68 genes present within the core genome of E. faecalis are upregulated in biofilm formation. One of those 68 genes is a putative selenium-dependent molybdenum hydroxylase (SDMH). Adjacent to this gene are a series of open reading frames that have been postulated to play a role in the maturation of a labile selenium cofactor. The biosynthesis of this labile cofactor has yet to be studied at either the genetic or biochemical level. The addition of selenium to growth medium caused a significant increase in biofilm density and extracellular hydrogen peroxide by wild type E. faecalis. By site-directed mutagenesis gene products encoded in the SDMH operon were shown to be necessary for the selenium-dependent biofilm formation as well as extracellular hydrogen peroxide production. This biofilm and peroxide phenotype is inhibited both by tungsten or auranofin in wild type E. faecalis suggesting the SDMH is a necessary enzyme for selenium-dependent biofilm and peroxide formation. These results show that the gene products encoded within the SDMH operon are necessary for a selenium-dependent biofilm formation as well as extracellular hydrogen peroxide production. These mutants will provide the basis for defining the synthesis of the labile selenium cofactor and allow for an expanded understanding of the biological use of selenium.
Show less - Date Issued
- 2010
- Identifier
- CFE0003420, ucf:53152
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003420
- Title
- BIOSTABILITY IN DRINKING WATER DISTRIBUTION SYSTEMS IN A CHANGING WATER QUALITY ENVIRONMENT USING CORROSION INHIBITORS.
- Creator
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Zhao, Bingjie, Randall, Andrew, University of Central Florida
- Abstract / Description
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In this study, the bacterial growth dynamics of 14 pilot drinking water distribution systems were studied in order to observe water quality changes due to corrosion inhibitor addition. Empirical models were developed to quantity the effect of inhibitor type and dose on bacterial growth (biofilm and bulk water). Water and pipe coupon samples were taken and examined during the experiments. The coupons were exposed to drinking water at approximately 20 °C for at least 5 weeks to allow the...
Show moreIn this study, the bacterial growth dynamics of 14 pilot drinking water distribution systems were studied in order to observe water quality changes due to corrosion inhibitor addition. Empirical models were developed to quantity the effect of inhibitor type and dose on bacterial growth (biofilm and bulk water). Water and pipe coupon samples were taken and examined during the experiments. The coupons were exposed to drinking water at approximately 20 °C for at least 5 weeks to allow the formation of a measurable quasi- steady-state biofilm. Bulk water samples were taken every week. In this study, two simple but practical empirical models were created. Sensitivity analysis for the bulk HPC model (for all 14 of the PDSs) showed that maintaining a chloramine residual at 2.6 mg/L instead of 1.1 mg/L would decrease bulk HPC by anywhere from 0.5 to 0.9 log, which was greater than the increase in bulk HPC from inhibitor addition at 0.31 to 0.42 log for Si and P based inhibitors respectively. This means that maintaining higher residual levels can counteract the relatively modest increases due to inhibitors. BF HPC was affected by pipe material, effluent residual and temperature in addition to a small increase due to inhibitor addition. Biofilm density was most affected by material type, with polyvinyl chloride (PVC) biofilm density consistently much lower than other materials (0.66, 0.92, and 1.22 log lower than lined cast iron (LCI), unlined cast iron (UCI), and galvanized steel (G), respectively). Temperature had a significant effect on both biofilm and bulk HPC levels but it is not practical to alter temperature for public drinking water distribution systems so temperature is not a management tool like residual. This study evaluated the effects of four different corrosion inhibitors (i.e. based on either phosphate or silica) on drinking water distribution system biofilms and bulk water HPC levels. Four different pipe materials were used in the pilot scale experiments, polyvinyl chloride (PVC), lined cast iron (LCI), unlined cast iron (UCI), and galvanized steel (G). Three kinds of phosphate based and one silica based corrosion inhibitors were added at concentrations typically applied in a drinking water distribution system for corrosion control. The data showed that there was a statistically significant increase of 0.34 log in biofilm bacterial densities (measured as HPC) with the addition of any of the phosphate based inhibitors (ortho-phosphorus, blended ortho-poly-phosphate, and zinc ortho-phosphate). A silica based inhibitor resulted in an increase of 0.36 log. The biological data also showed that there was a statistically significant increase in bulk water bacterial densities (measured as heterotrophic plates count, HPC) with the addition of any of the four inhibitors. For bulk HPC this increase was relatively small, being 15.4% (0.42 log) when using phosphate based inhibitors, and 11.0% (0.31 log) for the silica based inhibitor. Experiments with PDS influent spiked with phosphate salts, phosphate based inhibitors, and the silicate inhibitor showed that the growth response of P17 and NOx in the AOC test was increased by addition of these inorganic compounds. For this source water and the PDSs there was more than one limiting nutrient. In addition to organic compounds phosphorus was identified as a nutrient stimulating growth, and there was also an unidentified nutrient in the silica based inhibitor. However since the percentage increases due to inhibitors were no greater than 15% it is unlikely that this change would be significant for the bulk water microbial quality. In addition it was shown that increasing the chloramines residual could offset any additional growth and that the inhibitors could help compliance with the lead and copper rule. However corrosion inhibitors might result in an increase in monitoring and maintenance requirements, particularly in dead ends, reaches with long HRTs, and possibly storage facilities. In addition it is unknown what the effect of corrosion inhibitors are on the growth of coliform bacteria and opportunistic pathogens relative to ordinary heterotrophs. A method was developed to monitor precision for heterotrophic plate count (HPC) using both blind duplicates and lab replicates as part of a project looking at pilot drinking water distribution systems. Precision control charts were used to monitor for changes in assay variability with time just as they are used for chemical assays. In adapting these control charts for the HPC assay, it was determined that only plate counts ≥ 30 cfu per plate could be used for Quality Assurance (QA) purposes. In addition, four dilutions were used for all known Quality Control (QC) samples to insure counts usable for QC purposes would be obtained. As a result there was a 50% increase in the required labor for a given number of samples when blind duplicates and lab replicates were run in parallel with the samples. For bulk water HPCs the distributions of the duplicate and replicate data were found to be significantly different and separate control charts were used. A probability based analysis for setting up the warning limit (WL) and control limit (CL) was compared with the method following National Institute of Standard and Technology (NIST) guidelines.
Show less - Date Issued
- 2007
- Identifier
- CFE0001947, ucf:47452
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001947
- Title
- ANALYSIS OF THE PREVENTION OF BIOCORROSION CAUSED BY DESULFOVIBRIO ALASKENSIS G20.
- Creator
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Boring, Michael, Self, William, University of Central Florida
- Abstract / Description
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Desulfovibrio alaskensis G20 and other sulfate-reducing bacteria cause significant damage to metal pipelines and other infrastructure through a metabolic pathway that releases toxic hydrogen sulfide into their surroundings. The biocorrosion that results from the release of hydrogen sulfide creates significant economic burden, and can pose health risks for those exposed to this chemical. They are commonly present in the form of biofilms, an extracellular matrix composed of bacterial cells,...
Show moreDesulfovibrio alaskensis G20 and other sulfate-reducing bacteria cause significant damage to metal pipelines and other infrastructure through a metabolic pathway that releases toxic hydrogen sulfide into their surroundings. The biocorrosion that results from the release of hydrogen sulfide creates significant economic burden, and can pose health risks for those exposed to this chemical. They are commonly present in the form of biofilms, an extracellular matrix composed of bacterial cells, polysaccharides, proteins, nucleic acids, and other materials. These biofilms are difficult to remove, and they provide protection to the bacteria within from anti-bacterial treatments. Desulfovibrio alaskensis G20 is a strain derived from a wild-type bacterium collected from an oil well corrosion site and is a model organism for understanding biofilm formation of sulfate-reducing bacteria and how these biofilms can be prevented or inhibited by techniques such as cerium oxide nanoparticle coating. To this end, samples of Desulfovibrio alaskensis G20 were grown anaerobically in 24-well and 96-well plates, and the resultant biofilm growth was measured through spectrophotometry. Several different environmental parameters were tested, including temperature, electron donor molecules, basal and enriched growth media, and oxidative stress, revealing several affinities for production of biofilm growth.
Show less - Date Issued
- 2017
- Identifier
- CFH2000263, ucf:45942
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000263
- Title
- An Assessment of Biosorption Activated Media for the Removal of Pollutants in Up-Flow Stormwater Treatment Systems.
- Creator
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Hood, Andrew, Randall, Andrew, Wanielista, Martin, Chopra, Manoj, O'Reilly, Andrew, Moore, Sean, University of Central Florida
- Abstract / Description
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Nitrogen and phosphorus are often the limiting nutrients for marine and freshwater systems respectively. Additionally, stormwater often contains elevated levels of pathogens which can pollute the receiving water body and impact reuse applications [1-4]. The reduction of limiting nutrients and pathogens is a common primary target for stormwater best management practices (BMPs) [5]. Traditional BMPs, such as retention/detention treatment ponds require large footprints and may not be practical...
Show moreNitrogen and phosphorus are often the limiting nutrients for marine and freshwater systems respectively. Additionally, stormwater often contains elevated levels of pathogens which can pollute the receiving water body and impact reuse applications [1-4]. The reduction of limiting nutrients and pathogens is a common primary target for stormwater best management practices (BMPs) [5]. Traditional BMPs, such as retention/detention treatment ponds require large footprints and may not be practical in ultra-urban environments where above ground space is limited. Upflow filters utilizing biosorption activated media (BAM) that can be placed underground offer a small footprint alternative. Additionally, BAM upflow filters can be installed at the discharge point of traditional stormwater ponds to provide further treatment. This research simulated stormwater that had already been treated for solids removal; thus, most of the nutrients and solids in the influent were assumed to be as non-settable suspended solids or dissolved solids. Three different BAM mixtures in an upflow filter configuration were compared for the parameters of nitrogen, phosphorus, total coliform, E. coli, and heterotrophic plate count (HPC). Additionally, genetic testing was conducted using Polymerase Chain Reaction (PCR), in conjunction with a nitrogen mass balance, to determine if Anammox was a significant player in the nitrogen removal. The columns were run at both 22-minute and 220-minute Empty Bed Contact Times (EBCTs). All the BAM mixtures analyzed were shown to be capable at the removal of nitrogen, phosphorus, and total coliform during both the 22-minute and 220-minute EBCTs, with BAM #1 having the highest removal performance for all three parameters during both EBCTs. All BAM mixtures experienced an increase in HPC. Additionally, PCR analysis confirmed the presence of Anammox in the biofilm and via mass balance it was determined that the biological nitrogen removal was due to Anammox and endogenous denitrification with Anammox being a significant mechanism.
Show less - Date Issued
- 2019
- Identifier
- CFE0007817, ucf:52875
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007817
