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Lecture 7

MCB 3020 Lecture 7: Microbiology lecture 7 exam one

3 Pages
82 Views
Fall 2017

Department
Microbiology and Cell Science
Course Code
MCB 3020
Professor
Abdolkarim Asghari
Lecture
7

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9/9/2017
Microbiology Lecture 7Exam One
Growth is effected by temperature and pH
Effects of NaCl on Growth
Halophiles: grow optimally at >0.2 M
Extreme halophiles: require >2 Mrequire high salt concentrations
Effects of pH on growth
Aidophiles’ Alkalophiles withstad 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 Minimalfarthest left and low on graph
o Maximalfurthest right side and low on graph
o OptimalGrows 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 anaerobecannot live in presence of oxygen
Obligate aerobecan live in presence of oxygen
Facultativegrow better in presence of oxygen
Sources of Carbon, Energy and Electrons
Cells must have a carbon, energy and electron source
Fix CO2 absorption from environmentAutotrophs
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
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Description
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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