USGS Professional Pages
Research MicrobiologistContact Info
Dave, scientist for a USGS National Research Program (NRP) project since 1987, investigates microbe-contaminant interactions. Although focused on microbe/pathogen fate & persistence in hydrogeological systems; recent work examined antimicrobial mechanisms of therapeutic clays, how antibiotics affect aquifer microbial communities, & field-scale bacterial chemotaxis. The USGS multidisciplinary laboratory at CU, Boulder has collaborative ties to domestic academic institutions & governmental agencies.
Read Full Professional Summary
A full list of publications since 1987 is listed at Dave's other professional page:
My USGS Science Strategy AreasUnderstanding Ecosystems & Predicting Ecosystems Change
The Role of Environment and Wildlife in Human Health
Energy & Minerals for America's Future
A National Hazard, Risk, and Resilience Assessment Program
== Changes in chemical constituents of contaminated and uncontaminated sites can substantially influence the degree of microbial attachment to aquifer sediments (Harvey et al., 2011), may affect potential bioremediation of contaminated sites (Toepfer et al, 2012, Wang et al, 2008), influence pathogen attenuation and water quality (Metge et al, 2011, Mohanram et al., 2011) and affect microbial processes (Haack et al, 2012, Underwood et al., 2011). These studies have concentrated on delineating how specific classes of organic compounds and inorganic geochemistry affect bacterial attachment on sediments and affect their physiology. Some compounds (e.g. certain non-ionic surfactants, antibiotics) affect microibial attachment, attenuation and other biolgical processes at low (ppb) levels.
== Elucidation of antimicrobial mechanisms for therapeutic clays. As a result of experimentation undertaken and methods developed in our laboratory, we provided some possible explanations for antimicrobial activity of therapeutic clays used to treat skin infections. This is an example of public health microbiology, muldisciplinary research endeavor, and serendipitous discovery. Research has resulted in several presentations, a publication (Williams et al, 2012) and a provisional patent award (2009). Additionally, we identified at least one agent which, present in trace quantities, would render non therapeutic clays potentially antimicrobial.
== Results from flow-through column experiments demonstrated an understanding of microbial transport processes operational and field and column scales (Metge et al, 2010, 2011, Harvey et al, 2010, 2011) to field-scale subsurface microbial transport experiments. These small, simple experiments allow applicability across a variety of disciplines such as microbial transport, microbial ecology and/or public health microbiology.
== Development of genetically-engineered microorganisms. In 2005-2007, outreach with local high school students yielded modification and sucessful genetic engineering of a bacterial isolate which produced an internal fluorescent tag, later in sucessful field-scale demonstration of bacterial chemotaxis. This was in collaboration with University of Virginia, Charlottesville on a NSF-funded project that entailed several field tests. A blue-fluorescing protein (BFP) motile Pseudomonas mutant was employed in field and lab scale studies. A recent development included using transposon mediated genetic insertions of GFP and RFP into a 4-methyl, benzoate degrading Pseudomonad for real time microbial trackng in future contaminant degradation experiments.
== Method for dual isotope labeling of bacteriophage protein coat and nucleic acid. In 1997, we modified methods for differentially labeling protein coat and nucleic acid components of bacteriophage PRD1. This virus (PRD1) serves as a surrogate for field tests investigating pathogenic virus transport. Previous single-label methods would label both virus coat and nucleic acid components indiscriminately with the same label. The method allows us to assess if and by what mechanisms viruses become inactivated in the subsurface, and determined viral inactivation rates in subsurface material(s).
3215 Marine St, Bldg 6
Boulder, CO 80309
303-541-3084 - Fax
Back to top