Bacterial biofilms are formed by communities that are embedded in a self-produced matrix of extracellular polymeric substances (EPS). Importantly, bacteria in biofilms exhibit a set of 'emergent properties' that differ substantially from free-living bacterial cells. In this Review, we consider the fundamental role of the biofilm matrix in establishing the emergent properties of biofilms, describing how the characteristic features of biofilms - such as social cooperation, resource capture and enhanced survival of exposure to antimicrobials - all rely on the structural and functional properties of the matrix. Finally, we highlight the value of an ecological perspective in the study of the emergent properties of biofilms, which enables an appreciation of the ecological success of biofilms as habitat formers and, more generally, as a bacterial lifestyle.

Biofilms: an emergent form of bacterial life.

The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

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The Environmental Protection Agency

Dissolved organic matter (DOM) in soils plays an important role in the biogeochemistry of carbon, nitrogen, and phosphorus, in pedogenesis, and in the transport of pollutants in soils. The aim of this review is to summarize the recent literature about controls on DOM concentrations and fluxes in soi

Controls on the dynamics of dissolved organic matter in soils: a review.

The major potential environmental impacts related to landfill leachate are pollution of groundwater and surface waters. Landfill leachate contains pollutants that can be categorized into four groups (dissolved organic matter, inorganic macrocomponents, heavy metals, and xenobiotic organic compounds). Existing data show high leachate concentrations of all components in the early acid phase due to strong decomposition and leaching. In the long methanogenic phase a more stable leachate, with lower concentrations and a low BOD/COD-ratio, is observed. Generally, very low concentrations of heavy metals are observed. In contrast, the concentration of ammonia does not decrease, and often constitutes a major long-term pollutant in leachate. A broad range of xenobiotic organic compounds is observed in landfill leachate. The long-term behavior of landfills with respect to changes in oxidation-reduction status is discussed based on theory and model simulations. It seems that the somewhere postulated enhanced release of accumulated heavy metals would not take place within the time frames of thousands of years. This is supported by a few laboratory investigations. The existing data and model evaluations indicate that the xenobiotic organic compounds in most cases do not constitute a major long-term problem. This may suggest that ammonia will be of most concern in the long run.

/pdf/present-and-long-term-composition-of-msw-landfill-leachate-a-3m0wrwx61g.pdf

Present and long-term composition of msw landfill leachate: a review

Antimicrobial nanomaterials for water disinfection and microbial control: Potential applications and implications

Colloid mobilization and transport in groundwater

Influence of Dissolved Organic Matter on the Environmental Fate of Metals, Nanoparticles, and Colloids George R. Aiken,* Heileen Hsu-Kim, and Joseph N. Ryan U.S. Geological Survey, 3215 Marine Street, Boulder, Colorado 80303, United States Department of Civil and Environmental Engineering, Duke University, Box 90287, Durham, North Carolina 27708, United States Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, Colorado 80309, United States

Influence of Dissolved Organic Matter on the Environmental Fate of Metals, Nanoparticles, and Colloids

The binding of Hg(II) to dissolved organic matter (DOM; hydrophobic acids isolated from the Florida Everglades by XAD-8 resin) was measured at a wide range of Hg-to-DOM concentration ratios using an equilibrium dialysis ligand exchange method. Conditional distribution coefficients (K(DOM)') determined by this method were strongly affected by the Hg/DOM concentration ratio. At Hg/DOM ratios below approximately 1 microg of Hg/mg of DOM, we observed very strong interactions (K(DOM)' = 10(23.2+/-1.0) L kg(-1) at pH = 7.0 and I = 0.1), indicative of mercury-thiol bonds. Hg/DOM ratios above approximately 10 microg of Hg/mg of DOM, as used in most studies that have determined Hg-DOM binding constants, gave much lower K(DOM)' values (10(10.7+/-1.0) L kg(-1) at pH = 4.9-5.6 and I = 0.1), consistent with Hg binding mainly to oxygen functional groups. These results suggest that the binding of Hg to DOM under natural conditions (very low Hg/DOM ratios) is controlled by a small fraction of DOM molecules containing a reactive thiol functional group. Therefore, Hg/DOM distribution coefficients used for modeling the biogeochemical behavior of Hg in natural systems need to be determined at low Hg/DOM ratios.

Binding of mercury(II) to dissolved organic matter: The role of the mercury-to-DOM concentration ratio

The role of ζ-(zeta)potential of mineral grains in the initial deposition kinetics of colloidal particles in geochemically heterogeneous porous media is investigated. Colloid deposition experiments...

Joseph N. Ryan

Papers

Colloid mobilization and transport in groundwater

Influence of Dissolved Organic Matter on the Environmental Fate of Metals, Nanoparticles, and Colloids

Binding of mercury(II) to dissolved organic matter: The role of the mercury-to-DOM concentration ratio

Relative Insignificance of Mineral Grain Zeta Potential to Colloid Transport in Geochemically Heterogeneous Porous Media

The promise of bank filtration.