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Lecture 7

MCB 3020 Lecture 7: Microbiology lecture 7 exam one

3 Pages

Microbiology and Cell Science
Course Code
MCB 3020
Abdolkarim Asghari

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9/9/2017 Microbiology Lecture 7—Exam One • Growth is effected by temperature and pH Effects of NaCl on Growth • Halophiles: grow optimally at >0.2 M • Extreme halophiles: require >2 M—require high salt concentrations Effects of pH on growth • Acidophiles’ Alkalophiles withstand high/low pH • Most maintain an internal pH near neutrality o Plasma membrane is impermeable to protons o Some synthesize protective proteins ▪ E.g., acid-shock proteins o Many change pH of their habitat by producing acidic/basic products o Most media contain buffers to prevent growth inhibition Temperature • Organisms exhibit distinch cardinal growth temperatures o Minimal—farthest left and low on graph o Maximal—furthest right side and low on graph o Optimal—Grows best here. Optimum is highest height on graph Oxygen Concentration • Consumption of oxygen can result in toxic by- product like peroxides, super oxides, free radicals • Whoever grows in presence of oxygen must have enzymes like SOD, Catalase (neutralizes peroxides) • Strict anaerobe—cannot live in presence of oxygen • Obligate aerobe—can live in presence of oxygen • Facultative—grow better in presence of oxygen Sources of Carbon, Energy and Electrons • Cells must have a carbon, energy and electron source • Fix CO2 absorption from environment—Autotrophs • Heterotrophs carbon sources are organic • Energy sources: Phototrophs (light), chemotrophs (oxidation of organic inorganic compounds) • Electron sources: Lithotrophs (reduced inorganic molecules), Organotrophs (organic molecules) Nutritional Types of Microorganisms • Major ones: o Photolithoautotroph. Carbon source: CO2. Energy source: light. Electron source: inorganic e- source o Chemolithoautotroph. Carbon source: CO2. Energy source: inorganic molecules. Electron source: inorganic e- donors Biofilms • Ubiquitous in nature • Complex, slime enclosed colonies attached to surfaces • Form on medical devices such as impoants often lead to illness • Microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA-Biofilm is produced • Interactions occur among attached organisms • Extracellular matrix and change in attached organisms, and protects them from UV light and antibiotics • Sloughing off of organisms result in contamination of surroundings Cell deposits and absorb process: 1. Substratum preconditioning to ambient molecules 2. Cell deposition 3. Cell adsorption 4. Desorption 5. Cell-to-cell signaling and onset of exopolymer production 6. Convection and diffusive transport of O2 and nutrients 7. Replication and growth 8. Secretion of polysacch
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