Novel molecular tags for the detection and quantitation of potentially pathogenic microbes and microbial toxins in drinking water. Barney Bishop

Our goal is to develop technologies that will allow the detection of the presence of potentially pathogenic microbes and microbial toxins in drinking water. Towards these ends we will engineer proteins and nanoparticles to serve as colorimetric and fluorescent reporters for detecting the presence toxins and other molecules associated with selected microbes in water.  Initial efforts will focus on introducing binding sites for known bacterial toxins into fluorescent proteins (such as green fluorescent protein) in such a way that these proteins are fluorescent only when the site is occupied.  Using a fluorescent reporter should allow detection and low concentrations and signal intensity.  Green fluorescent protein (GFP) provides an ideal platform for engineering the desired fluorescent reporter.  There is an extensive body of published information regarding green fluorescent protein and features that are essential to its proper folding and formation of the fluorophore, which will provide the foundation for our reengineering efforts.  Additionally, extensive work has been done modifying the excitation and emission wavelengths and enhancing signal intensity in GFP. As the project progresses ligand specificity and sensitivity of the reporter proteins will be refined.  While efforts will primarily focus on protein-based reporters, thermo-responsive acrylamide-based nanoparticles with covalently incorporated fluorophore will also be investigated. Ultimately, it is envisioned that an array of these proteins or particles could be engineered to allow the detection of a broad spectrum of microbes and toxins in water, without requiring sending samples to a lab for analysis.

 Pesticides in Sediments and Water. Shahamat U. Khan

About one billion pounds of pesticides are used each year in the United States to control weeds, insects, and other organisms. About 80 % of this quantity is used in agriculture. Although the use of pesticides has resulted in increased crop production and other benefits, it has raised concerns about the potential adverse effects on the environment and human health.  In many respect, the greatest potential for unintended adverse effects of pesticides is through contamination of the hydrologic system. Water is one of the primary pathways by which pesticides are transported from their application areas to other parts of the environment.

There is considerable information in the literature on pesticides in bed sediments and aquatic biota in rivers and estuaries. However, still there are gaps in our standing of the distribution and trend in pesticide contamination in bed sediments and aquatic biota. There is little known on the extent of contamination of currently used pesticides, including the few organochlorine insecticides still permitted for use in agriculture as well as certain pesticides that are moderately hydrophobic and moderately persistent. Although large scale monitoring of these compounds in stream sediments and aquatic biota may not be warranted, it may be reasonable to monitor such pesticides in areas of known high or repeated use, or in association with specific land use or crops. There is much to be learned about the biological significance of pesticide residues in hydrologic systems. Some research areas are particularly compelling: for example, the effects of chemical mixtures and potential adverse effects on aquatic life, wildlife, human health due to endocrine disruption.

It is hoped that in the new center a multidisciplinary research efforts that combine chemistry, hydrology, and ecotoxicology will provide a more complete perspective of the occurrence, distribution and significance of pesticides in bed sediments and biota of rivers and lakes which support aquatic life and related food chains and is used for recreation, drinking water, irrigation, and many other purposes.

Meso-scale treatment of impervious surface runoff using Palygorskite minerals.  Mark Krekeler and Gregory D. Foster

Inexpensive and effective technologies for controlling non-point source pollution are critical to long term water quality sustainability.  One strategy of implementation is a distributed approach where technologies are inserted at a meso-scale level in regions where pollution occurs rather than in centralized treatment plants where pollution is collected after passing through and contaminating large portions of the environment.  

A recognized mineral based material group suitable for this application is the palygorskite mineral group.  Specimens from this mineral group commonly have surface areas of 200- 600 m2/g and have a strong affinity for absorbing a wide range of organic molecules. The large sorption capacity is primarily controlled by two factors: 1) mineral-fiber surfaces and 2) the zeolite-like channels that run the length of the fibers. Mineal-fiber surfaces have silanol groups, surficial oxygen
atoms, and structural H₂O (often referred to as OH₂ to distinguish it from zeolitic H₂O), along with broken bonds. These features allow organic molecules and cations to interact with the mineral surface. 

Versions of granulated palygorskite media have been investigated by Krekeler and Foster and a media suitable for use in mesoscale pollution reduction technologies has been identified. Bagged palygorskite media will be installed in selected parking lot drainage sites at GMU. The efficacy of palygorskite media for sorption of common petrochemical pollutants derived from parking lots will be determined. This work is expected to result in several academic publications and modifications of this approach may be developed for GMU patents through the office of technology transfer. 

Optimization of siderophore molecules for removal of metals from drinking water. Tim Born

Siderophores are molecules produced primarily by bacteria for the purpose of harvesting ferric iron from the environment. Iron-limiting conditions stimulate the synthesis of these molecules and they are exported from the cell to scavenge
iron.  Complexes between siderophores and Fe³⁺ are extremely stable, with formation constants of 1030 or greater. In addition to iron, siderophores are known to bind metals such as gallium and aluminum, but they do not bind to divalent metal ions. The goal of this project will be to optimize siderophore structures for the complexation of metals other then Fe(III). Siderophores produced by organisms differ widely in structure, suggesting there are many ways to make these chelators and many modifications that can be accommodated. Genes encoding siderophore biosynthesis will be cloned from a representative set of microorganisms and expressed in E. coli.  Random mutagenesis will then be performed and the new siderophores will be tested for their ability to bind Fe(III) as well as other metal contaminants commonly found in water.  Optimization for individual metals will continue based on the results of initial experiments.  The hope is that novel siderophores that form stable complexes with metals other then Fe(III) will be identified.

Tethering of antibiotics and “bacterial glues” to composite iron matrix. Tim Born

Siderophores are molecules produced primarily by bacteria for the purpose of harvesting ferric iron from the environment. Iron-limiting conditions stimulate the synthesis of these molecules and they are exported from the cell to scavenge iron.  Complexes between siderophores and Fe³⁺ are extremely stable, with formation constants of 1030 or greater.  The composite iron matrix (CIM) that is the active component of the SONO filter developed by Dr. Abul Hussam contains Fe(III), thus siderophores should bind tightly to the CIM.  The focus of this project will be to use siderophores to tether antibiotics or bacterial-binding compounds to the CIM.  The structure shown below of a typical citrate-hydroxamate siderophore illustrates the iron-binding site on the right and also reveals possible sites for linkage of other compounds. The tight association between the CIM and the siderophore will anchor the attached compounds within the SONO filter where they can be used for water treatment. Although it would be attractive to append antibiotics to a siderophore molecule, it may be more beneficial use compounds that bind to surface of bacteria.  Although the bacteria will not be killed in this situation, they will be bound to the filter and removed from the drinking.  Acidic conditions can be used to release the siderophores, along with their attached bacteria, from the filter and the filter can then be regenerated with a new batch of compounds.

Rapid measurement methodology and the removal of radioactivity from well water using surface adsorption technology. Douglas Mose

Our goal is to determine where and why well water used in homes often exceeds the US-EPA recommended radioactivity maximum of 300 pCi/L, and to reduce the concentrations in potable water. It now appears that the regional average is about 2,500 pCi/L. There appears to be some rock types that usually produce higher than average waterborne radioactivity, and it appears that water table depth and rainfall can influence the waterborne radioactivity concentrations. Experiments show that adsorption tanks of activated charcoal are effective in greatly reducing the concentratiuons, though different types of charcoal have different removal characteristics.

Rainwater precipitation of mercury. Douglas Mose

Our goal is to examine the annual rain and snow precipitation patterns of mercury, primarily using measurements taken at our field station in central Virginia and other nation-wide stations that participate in the USGS/USEPA National Atmospheric Deposition Program. It now appears that the average local mercury concentration in rainfall is about 7.5 ng/L, but strong upward and downward concentration changes are seen to be associated with unusual weather conditions. The locations of point sources of mercury emission remain elusive.

Waterborne radioactivity and its influence on the development of cancer.
Douglas Mose

Our goal is to evaluate the influence that airborne radioactivity, out-gassed from potable water brought into homes by well water, has on the development of lung, blood and other types of cancer among the home occupants. Studies show that indoor airborne radioactivity is a mixture of radioactive soil gas and waterborne gas. Systems to mitigate soil gas appear to have little effect on the influx of waterborne radioactivity. Our studies show that the percentage of waterborne radioactivity that reaches the home occupants is determined, in part, by the size of the home, the length of the time required for groundwater radioactivity to enter the home environment, and the depth of the water table. 

Removal of hydrocarbon contamination from soil. Douglas Mose

Our goal is to monitor and evaluate the mitigation of hydrocarbon contamination in soils of fine particle size, known to be difficult to bring back to their pre-contamination condition. Deeply weathered soils, found world-wide and in the central Appalachian states, may be of particular concern when they underlie densely populated areas where many large and small hydrocarbon storage facilities are in constant use. Excavation often  cannot be used for mitigation due to the requisite disruption of roads, commercial activities and homes. Our interests lie in evaluating the success of prolonged less aggressive methodology. Current projects involve a group of storage tanks that lost over 200,000 gallons of various fuels in the 1980’s, and in numerous leaks from tanks that contained a few hundred to a few thousand gallons of fuel. 

Development of greenhouse air and water systems using photovoltaic electrical power. Douglas Mose