chapter_28 - Foundations of Microbial Ecology symbioses...

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1 Chapter 28 Microorganism Interactions and Microbial Ecology Foundations of Microbial Ecology symbioses relationships among organisms in an ecosystem populations assemblages of similar organisms communities mixtures of different populations ecosystems self-regulating biological communities and their physical environment Microbial Interactions physical associations ectosymbiont organism located on surface of another organism (usually larger) consortium physical contact between dissimilar organisms of similar size endosymbiotic organism located within another organism ecto/endosymbiosis organism lives both on inside and outside of another organism
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2 Figure 28.1 Mutualism some reciprocal benefit to both partners relationship with some degree of obligation often partners cannot live separately mutualist and host are metabolically dependent on each other e.g., protozoan-termite relationship termite provides food for protozoan protozoan digests cellulose in wood particles, providing nutrients for termite
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3 Sulfide-based mutualisms Figure 28.4 vent fluids – anoxic with temperatures up to 350°C surrounding sea water up to ~25 °C Figure 28.5 The rumen ecosystem ruminants animals that have stomach divided into four compartments and chew a cud rumen one of compartments contains large, diverse population of microbes Figure 28.6 Ruminant stomach
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4 Cooperation both organisms benefit nonobligatory syntrophic relationship Syntrophism growth of one organism depends on or is improved by growth factors, nutrients, or substrates provided by another organism growing nearby also called crossfeeding or satellite phenomenon Figure 28.7 OM = organic material Examples of cooperation Commensalism one organism benefits and the other is neither harmed nor helped commensal organism that benefits often syntrophic can also involve modification of environment by one organism, making it more suited for another organism
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5 An example of commensalism nitrification NH 3 NO 2 NO 3 carried out by two different bacteria e.g., Nitrosomonas carries out first step e.g., Nitrobacter carries out second step (i.e., it benefits from its association with Nitrosomonas ) More examples nonpathogenic E. coli in human colon E. coli - Bacteroides interaction E. coli consumes oxygen creating suitable anaerobic environment for Bacteroides More examples microbial succession during spoilage of milk fermentative bacteria produce acids that promote growth of acid tolerant species formation of biofilms initial colonizer makes it possible for other microorganisms to attach skin or surface microbes on plants or animals host plant or animal releases volatile, soluble, and particulate organic compounds, which are used by
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This note was uploaded on 01/11/2009 for the course BICS 300 taught by Professor Dr.d.w.smith during the Spring '07 term at University of Dundee.

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chapter_28 - Foundations of Microbial Ecology symbioses...

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