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19 Cards in this Set
- Front
- Back
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Microbial Ecology
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-the science of how microorganisms affect and are affected by the environment
-the diversity and activity of microbes in their natural environment -why does it matter? homeostasis on earth |
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Microbial Activity
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sustains life on earth
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Methods in Microbial Ecology
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-culture dependent analysis
-culture independent analysis -measuring microbial activities in nature |
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Enrichment Culture
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-performed when an organism with specific properties is needed for study or an application
-set up media in conditions that will allow growth of the organism : SELECTION and COUNTER SELECTION -obtain an inoculum from an environment where this organism is likely found |
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Martinus Beijerinck
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formulated idea of enrichment
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Enrichment Culture: Azotobacter
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to select for N fixing bacteria, you don't have N2 in the medium. if its in there, there will be no selective pressure for N2 fixation
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Methods to Isolate Culture
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-streak plate
-agar shake -most probably number (MPN) |
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Streak Plate and Agar Shake (to isolate a colony)
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-common practice: need 3 consecutive streaking of isolated colonies
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How to Know a Culture is Pure
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-16S rRNA gene
-microscopy -colony morphology -growth in media that favor contaminants |
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Selective Single Cell Isolation
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-another way to isolate a colony
-laser tweezers: measure forces of interaction: adhesion, attachment during conjugation -flow cytometry: cell sorting |
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Culture Dependent Analysis
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-most microbes in nature cannot be cultured
-enrichments and isolations disrupt microbial interaction |
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Fluorescent Staining
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-non specific; all cells stained
-counting microbial cells -no distinction between live and dead cells -intercalate into nucleic acids |
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Viability Staining
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-live= cells with intact cytoplasmic membranes
-limited use with environmental samples |
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Fluorescence in Situ Hybridization (FISH)
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-fluorescent probes that target 16S rRNA genes
-combined with flow cytometry: enumeration of specific groups of microbes in a large sample |
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CARD-FISH
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modification to detect gene expression (mRNA)
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Methods Based on PCR
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-gel electrophoresis
-clone libraries -DNA sequencing -phylogenetic analysis |
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Clone Libraries
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individual DNA fragments are cloned after RFLP and sequenced
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DGGE (gel electrophoresis)
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separation of individual bands based on differences in sequence composition and size
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Isotopic Fractionation
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biological processes discriminate against heavier isotopes and favor lighter isotopes
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