Lecture notes 10 8 - and parts of cells So when the...

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Lecture Notes: Microbiology October 8, 2008 Summary: Microbial Communities and Habitats, Biofilms, Lichens. Salinity -Higher salt concentration= lower water activity -Other low water activity environments: high sugar concentrations (osmophiles), desert environments - (Xerophiles) -15-30% NaCl required for growth for Halobacterium salinarum. High K+ accumulated inside cell. K+ is a compatible solute. -Other compatible solutes: amino acid=type solutes, carbohydrate, alcohol. These, when synthesized by the cell, will exist within the cell, and protect it from drying. To balance the osmotic difference. -Many of these cells will use a Na+ gradient instead of H+ for metabolism, transport. O2 Concentration Microaerophilic: likes oxygen in only very small amounts. In a test tube, they will make a band farther down in the tube, where the oxygen in approaching 0. When oxygen is present, in anaerobes hydrogen peroxide, superoxide is produced. These break down cell
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Unformatted text preview: and parts of cells. So, when the environment became oxygenic, bacteria had to find a way to break down h202, superoxide, via catalase, superoxide reductase/dismutase. Radiation-Resistance Mechanisms: Carotenoids (UV), DNA repair systems, Genetic redundancy (multiple chromosomes and plasmids, multiple copies of critical genes. -Most damaging radiation is ionizing radiation ( DNA and protein damage)-Highly radiation resistant bacteria: clostridium botulism, deinococcus radiodurans (five times the most resistant endospores). Antimicrobial Chemical Agents-Difference between antiseptic and disinfectant. Antiseptic: living tissue. Disinfectant: inanimate surfaces. Growth factor analogs: stop a certain enzymatic step: Sulfanilimides Microbial Ecology-The study of how microorganism interact with each other and their environments....
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