Rizzo lect 10a _11a

Rizzo lect 10a _11a - 1 Functional diversity Positive and...

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Functional diversity Positive and negative interactions with other organisms Global nutrient cycles Shaping earth history Industrial and agricultural uses
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3 acteria and archaea are key pathogens and commensals of any eukaryotes
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Microbes run global cycles http://www.fossweb.com/resources/pictures/16327852.gif
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Microbes run global cycles
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7 Based primarily on rRNA
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1) Spirochetes Gram-negative Motile Chemoheterotrophic Unique rotating, axial filaments (modified flagella) Many are pathogens: ± Syphilis ± Lyme disease Others free-living
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2) Chlamydias Gram-negative Cocci or rod-shaped Extremely small Live only as parasites within cells of other organisms Some are pathogens: ± Trachoma ± Multiple sexually transmitted diseases C. trachomatis
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3) High-GC Gram Positives (Actinobacteria) High G+C/A+T ratio in DNA Elaborate branching Some reproduce by forming chains of spores at tips of filaments Most antibiotics are from this group Causative agents of many diseases
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4) Cyanobacteria Photoautotrophic using chlorophyll a Contain internal membrane system for photosynthesis Chloroplasts are derived from endosymbiotic cyanobacteria Colonies can differentiate into vegetative cells,
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5) Low-GC Gram Positives (Firmicutes) Low G+C/A+T ratio in DNA Most Gram-positive Some produce endospores which are resistant “seeds” that germinate when conditions are good Many agents of diseases (e.g., anthrax, MRSA, Streptococcus, botulism, tetanus) Mycoplasmas
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6) Proteobacteria Largest group of bacteria – high diversity of metabolic phenotypes Gram-negative E. coli : important for genetic engineering, human pathogen Includes some nitrogen-fixing genera such as Rhizobium Includes many human
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Archaea: 2 major clades
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Orange: some members culturable Blue: known only from environmental samples Archaea
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Creanarchaeota Most are both thermophilic (heat loving) & acidophilic (acid-loving) Sulfolobus lives in hot sulfur springs (70–75°C, pH 2-3) One species of Ferroplasma lives at pH near 0
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Euryarchaeota: Methanogens Only known methanogens (produce methane (CH 4 ) by reducing CO 2 ) - form of chemoautotrophy Methanogens release 2 billion tons of methane per year Many live in the guts of grazing mammals Increased cattle farming and rice growing contributes methane to the atmosphere Many such as Methanopyrus live in deep-ocean hydrothermal vents
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Euryarchaeota: Halophiles (Salt lovers) Pink carotenoid pigments – very visible Have been found at pH up to 11.5. They live in the most salty, most alkaline environments on Earth Many have Bacteriorhodopsin which uses energy of light to synthesize ATP
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21 How to study microbes Some questions many people ask about microbes found in various places: ± Who are they? (i.e., what kinds of microbes are they) ± What are they doing ? (i.e., what functions and processes do they possess) The principles here apply to bacteria, archaea and eukaryotic microbes
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22 Extremophiles
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This document was uploaded on 08/21/2011.

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Rizzo lect 10a _11a - 1 Functional diversity Positive and...

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