black14 - Symbiosis Symbioses are intimate, relatively...

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Symbiosis Symbioses are intimate, relatively long- term interaction between organisms Typically at least one of the organisms benefits from the relationship We can classify Symbioses in terms of the degree to which the other organism (e.g., the host) benefits or is harmed: 1. Commensalism 2. Mutualism 3. Parasitism
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Commensalism “A Lion's Mane Jellyfish and a commensal fish. The fish lives with the jellyfish and hides in its tentacles for protection.” ( http://www. aquaimages.net/alaska .html ) The fish clearly gains. Does the jellyfish? Does the relationship cost the jellyfish anything? If neither, then this is an example of commensalism!
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Commensalism
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Normal Flora Normal flora are the ~harmless microorganisms found on your body Normal flora are found on every part of your body that normally comes in contact with outside world (deep lungs and stomach are exceptions) Normal flora can be transient or permanent (“transient” vs. “resident” microflora) Note that not all normal flora is always harmless – normal flora includes opportunitic pathogens, e.g., E. coli urinary tract infections
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Normal Flora
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Mutualism (lichen)
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Mutualism (3-way) “A remarkable 3-way mutualism appears to have evolved between an ant, a butterfly caterpillar, and an acacia in the American southwest. The caterpillars have nectar organs which the ants drink from, and the acacia tolerates the feeding caterpillars. The ants appear to provide some protection for both plant and caterpillar. Research of Diane Wagner, American Museum of Natural History Southwestern Research Station” ( http://www.dimijianimages.com/More-page5-mutualisms/3-way-mutualism. htm)
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Normal Flora Doing Good! Normal flora can help the host (e.g., you) by synthesizing vitamins (I.e., vitamin K) Normal flora can help the host by metabolizing materials into useful nutrients (e.g., cellulose digestion in termites, ungulates, and even primates) Normal flora can help the host by effecting Microbial Competition , a.k.a., Microbial Antagonism
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Parasitism Basically, all infectious pathogens are parasites That is, they harm their hosts in the course of stealing space, nutrients, and/or living tissue I.e., normal (and not so normal) flora doing bad!
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Disease Disease is a disturbance in the state of health Microbes cause disease in the course of stealing space, nutrients, and/or living tissue from their symbiotic hosts (e.g, us) To do this, microbes must: 1. Gain access to the host ( contamination ) 2. Adhere to the host ( adherence ) 3. Replicate on the host ( colonization ) 4. Invade tissues ( invasion ) 5. And produce toxins or other agents that cause host harm ( damage )
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Disease 1. Encounter : The agent meets the host 2. Entry : The agent enters the host 3. Spread : The agent spreads from the site of entry 4. Multiplication : The agent multiplies within
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This note was uploaded on 06/03/2011 for the course MCB 205 taught by Professor Abedon during the Spring '11 term at Ohio State.

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black14 - Symbiosis Symbioses are intimate, relatively...

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