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MULTIPLE IMAGING TECHNIQUES DEMONSTRATE THE MANIPULATION OF SURFACES TO REDUCE BACTERIAL CONTAMINATION
Arnold, J. W., D. H. Boothe, O. Susuki, AND G W. Bailey. MULTIPLE IMAGING TECHNIQUES DEMONSTRATE THE MANIPULATION OF SURFACES TO REDUCE BACTERIAL CONTAMINATION. Presented at First International Meeting on Applied Physics, Badajoz, Spain, October 13-18, 2003.
This task is divided into four major research areas: (1) Development of computational tools and databases for screening-level modeling of the environmental fate of organic chemicals; (2) Metabolism of xenobiotics: Enhancing the development of a metabolic simulator; (3) Metabonomics: The use of advanced analytical tools to identify toxicity pathways; and (4) Software infrastructure to support development and application of transformation/metabolic simulators.
For many chemicals, multiple transformation/metabolic pathways can exist. Consequently, transformation/metabolic simulators must utilize transformation rate data for prioritization of competing pathways. The prioritization process thus requires the integration of reliable rate data. When this data is absent, it is necessary to generate a database with metabolic and transformation rate constants based on: (1) experimentally measured values, including those requiring the use of advanced analytical techniques for measuring metabolic rate constants in vivo and in vitro; (2) rate constants derived from SPARC and mechanistic-based QSAR models; and (3) data mined from the literature and Program Office CBI. A long-term goal of this project is to build this database. This information will be used to enhance the predictive capabilities of the transformation/metabolic simulators. As indicated previously, exposure genomics, which provide early signs of chemical exposure based on changes in gene expression, will be used to guide chemical fate and metabolism studies. The incorporation of exposure genomics into fate studies will provide information concerning (1) the minimal concentrations at which biological events occur; and (2) the identification of biologically relevant chemicals(s) in mixtures.
The capability of categorizing chemicals and their metabolites based on toxicity pathway is imperative to the success of the CompTox Research Program. Metabonomics, which is the multi-parametric measurement of metabolites in living systems due to physiological stimuli and/or genetic modification, provides such a capability. The application of metabonomics to toxicity testing involves the elucidation of changes in metabolic patterns associated with chemical toxicity based on the measurement of component profiles in biofluids, and enables the generation of spectral profiles for a wide range of endogenous metabolites. Metabolic profiles can provide a measure of the real outcome of potential changes as the result of xenobiotic exposure.
Surface imaging techniques were combined to determine appropriate manipulation of technologically important surfaces for commercial applications. Stainless steel surfaces were engineered to reduce bacterial contamination, biofilm formation, and corrosion during product processing. The complementarity of microscopy methods, scanning electron microscopy (SEM), electron probe microanalysis, and atomic force microscopy (AFM) with spectrophotometry assessed and correlated form and function of surface modifications. All samples were examined by visual inspection and electron probe microanalysis for surface characteristics and elemental composition, respectively. Natural bacterial populations collected from the processing environment were assessed for their affinity to attach to sample surfaces. Aliquots of bacterial suspensions were diluted in broth and measured by spectrophotometry. Stainless steel disks (1-cm diameter) were added, and the cultures were grown to sufficient density to form monolayers of bacterial cells on control surfaces. The effects of microstructure with changes in manufacture were compared with the phenomena of bacterial interactions at surfaces and material interfaces. The disks for each surface treatment analyzed separately by AFM were cut from the same sheets used for SEM. Disks were examined directly. Relative differences in the surface morphology of stainless steel finishes, including fractal dimensions, Z ranges, roughness, and other measurements corresponded with the differences in reduction of bacterial counts shown by SEM. A model of wet-processing conditions tested the effects of corrosive treatment on bacterial attachment. The effects of rouging, corrosion, and biofouling are costly industrial problems. Bacterial attachment also affected the chemical processes of corrosive treatment at surfaces. The surface resistance achieved by electropolishing reduced bacterial numbers significantly from the other methods tested. In addition, the simplicity of the cleaning process and reduction in chemical use makes it attractive for industrial applications. The design of appropriate materials for the reduction of contamination during food processing necessitates an understanding of the forces of bacterial attachment and corrosion. Final selection of surface finishes is influenced by function and economy.
Record Details:Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
ECOSYSTEMS RESEARCH DIVISION
PROCESSES & MODELING BRANCH