2 items with the tag “extracellular polymeric substances

  • Extra-Cellular Polymeric Substances as Armor Against Cell Membrane Rupture on Mineral Surfaces
    NAI 2009 University of Wisconsin Annual Report

    Our interdisciplinary project examined the hypotheses that bacterial cell membranes are ruptured in contact with specific mineral surfaces, and that biofilm-forming extra-cellular polymeric substances (EPS) may have evolved to shield against membrane rupture (cell lysis). Furthermore, we proposed that mineral reactivity towards membranolysis should depend on its surface properties such as charge, reactive area, or free radicals generated by radiation and impacts on early Earth, Mars, and other worlds. The effect of EPS on preservation in the rock record will also be examined. By understanding the mechanisms for membranolysis, especially under the extreme conditions of high radiation and heavy impacts during early planetary history, the project addresses the NASA Astrobiology Institute’s (NAI) Roadmap goals of understanding the origins of cellularity, the evolution of mechanisms for survival at environmental limits, and preservation of biosignatures, and NASA’s Strategic Goal of advancing scientific knowledge of the origin and evolution of the Earth’s biosphere and the potential for life elsewhere.

    ROADMAP OBJECTIVES: 3.4 5.1 7.1
  • Project 2C: Role of Extracellular Polymeric Substances (EPS) and Bacteria Cell Wall Structure in Shielding Against Specific Mineral Toxicity - Implications for Cell Surface Evolution
    NAI 2011 University of Wisconsin Annual Report

    Our interdisciplinary project examined the hypotheses that (1) bacterial cell membranes are ruptured in contact with specific mineral surfaces, (2) biofilm-forming extra-cellular polymeric substances (EPS) may have evolved to shield against membrane rupture (cell lysis), (3) differences in cell-wall structure of Gram-negative and Gram-positive bacteria may influence the susceptibility of cells to toxic minerals and (4) mineral toxicity depends on its surface chemistry and nanoparticle size.

    Previously, we have examined Gram-negative P. aeruginosa strains, wild-type (PAO1) that is capable of generating copious amount of EPS and producing biofilms, as well as the knock-out mutant (Δ-psl) that is defective in its ability to form EPS and biofilms. In the 2010-2011 year of funding, we have expanded our study to include Gram-positive B. subtilis strains, biofilm-producing wild-type NCIB3610 and biofilm-defective mutant yhxBΔ. We confirmed the hypotheses (1), (2) and (4) for both Gram-negative and Gram-positive bacteria, with toxicity increasing as amorphous β-TiO2 < γ-Al2O3. We also confirmed hypothesis (3) that Gram-positive bacteria are less susceptible to mineral toxicity than Gram-negative because of the most robust cell-wall structure of the former. Finally, we have shown that the mechanisms of toxicity depends on mineral surface charge for initial adhesion of nanoparticles to the cell surface, nanoparticle size which determines whether the particles can enter the intracellular space (e.g., for γ-Al2O3), the presence of surface free radicals (e.g., β-TiO2 ) which would have been generated by UV-radiation and meteorite impacts on early Earth, Mars, and other worlds.

    By understanding the mechanisms for membranolysis, especially under the extreme conditions of high radiation and heavy impacts during early planetary history, the project addresses the NASA Astrobiology Institute’s (NAI) Roadmap goals of understanding the origins of cellularity, the evolution of mechanisms for survival at environmental limits, and preservation of biosignatures, and NASA’s Strategic Goal of advancing scientific knowledge of the origin and evolution of the Earth’s biosphere and the potential for life elsewhere.

    ROADMAP OBJECTIVES: 3.4 5.1 7.1