lecture 5 spring 09

lecture 5 spring 09 - Microbe-Microbe Interactions Symbiosis

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Microbe-Microbe Interactions
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Symbiosis The living together of two different kinds of organisms Mutualistic- both partners benefit Parasitic – one partner benefits at the expense of the other Term commonly used to denote mutualistic associations
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Simple Interactions Microbes live in communities and metabolize complex compounds in a cooperative manner, i.e., rumen Microbial communities make environments more hospitable for others, e.g. Some microbes can metabolize end products that reach inhibitory concentrations.
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Syntrophy Syntrophy is an interaction between organisms that combine their metabolic capabilities to catabolize substances that individuals cannot catabolize alone. The cell-cell interactions follow favorable thermodynamics even though individual reactions may be unfavorable. Some microbes that form syntrophic interactions are able to metabolize various
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Example: Saccharomyces cerevisiae deacidifies the environment allowing P seudomonas putida to Grapes contain a high concentration of glucose. P. putida can initially grow but because it ferments carbohydrates and acidifies the environment, it cannot survive for extended periods of time. When yeast are present it also metabolizes sugar which results in different end products of metabolism. Aerobically- carbon dioxide and water Anaerobically- carbon dioxide and ethanol
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Interactions are
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An enduring relationship Mitochondria and chloroplasts These organelles were once microbes Result of this symbiosis over years resulted in the development of the eukaryotic cell DNA evidence Mitochondrial DNA has homology with rickettsiae, an intracellular human parasite Chloroplast DNA has homology with photosynthetic cyanobacteria
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Additional evidence Mitochondria and chloroplasts divide by binary fission - Some retain proteins that are required for bacterial division Protein synthesis - Start with formylated methionine rather than methionine as in eukaryotes - Ribosomes resemble those of bacteria - Sensitive to antibiotic that inhibit bacterial protein synthesis
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Organelle-symbiont-
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Click to edit Master subtitle style Partners
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Nitrogen-fixing bacteria Not all organisms can reduce nitrogen, and those that DO NOT depend upon those that do Biological nitrogen fixation is carried out only by PROKARYOTES some living free other in association with plants Such associations found in trees (i.e., alders), shrubs (i.e., bayberry) or ferns Best studied examples in legumes
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between legume plants and
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This note was uploaded on 04/07/2009 for the course MICROBIO 303 taught by Professor Kaspar/escalnte/downs during the Spring '09 term at Wisconsin.

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lecture 5 spring 09 - Microbe-Microbe Interactions Symbiosis

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