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01.Isolations

Enterobacter aerogenes produce a bit of acid that

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Enterobacter aerogenes . produce a bit of Acid that precipitates the Eosin, resulting in Pink Colonies. E. coli produces a lot of Acid that precipitates the Methylene Blue, resulting in Purple Colonies surrounded by a Green Metallic Sheen. MacConkey Agar (Light Burgundy Color) MacConkey Agar contains Bile Salts and Crystal Violet that inhibit Gram Positive Bacteria and select for Enteric Bacteria. We’ll use MacConkey Agar when we determine the Number of Bacteria in Ground Beast in Lab 6.
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Lab 1 Page 21 Colony Morphology (Atlas Pages 19-26) We’ll be using our Microscopes to look at individual Bacteria but you can learn a lot by simply looking at the Morphology of Bacterial Colonies. At the very least, you can use Colony Morphology to look-out for Colonies that are Contaminants. Colony Configurations (Forms) Circular The Colonies look like little Dots. This is easily the most common Colony Configuration for our Bacteria. Irregular The Colonies look like Blobs or Amoebae. Bacillus and Azomonas in Lab 5 have irregular Colonies. Filamentous The Colonies look like Fungi. It’s definitely a Contaminant! Concentric The Colonies look like Rings within Rings. It’s a Contaminant. (L= circles within) Colony Margins (Edges) Entire The Edge is smooth, like a Drop of Water. This is a common Edge Morphology for our Bacteria. Undulate The Edge is wavy, like Lasagna. You’ll see several Bacillus sp. like this when we do Soil Isolates. Lobate The Edge is blobby, like a Lava Lamp. This is how Azomonas in Lab 5 looks. Erose The Edge is bayed, like Beach Erosion. Filamenous The Edge looks like a Fungus. Contaminant! Colony Elevations Flat The Colony does not rise above the Agar. Some but not all Bacillus sp. Raised The Colony is like a Mesa. Convex The Colony is like Half of a Lens. This is a very Common Colony Elevation for our Bacteria. Drop-like The Colony is like El Capitan. Azomonas in Lab 5. Umbonate The Colony is like a partially melted Chocolate Chip. (L= shield boss)
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Lab 1 Page 22 Background Information for Lab 1 Exercises Isolation of Bacteria in Pure Culture The Purpose of Bacterial Isolations in an Introductory Microbiology Lab like MIC 101 is two-fold: First, we’d like you to gain Experience in some of the more common Bacteriological Techniques; Second, we’d like you to become acquainted with the Characteristics of four widely-encountered, well-known Bacteria. There are two Fundamental Approaches to isolating a Specific Bacterium from the heterogeneous Population in a Natural Environment, be that Environment a Soil Sample or a “Patient” Sample. Direct Isolation Direct Isolation is used if the desired Bacterium is present as a High Percentage of the Organisms in its Natural Environment. We’ll use Direct Isolation to isolate Bacillus sp. from Soil, and Skin Bacteria (Micrococcus luteus ) from “Patient” Skin Swabs and Enteric Bacteria (E. coli and Enterobacter aerogenes ) from “Patient” Rectal Swabs. Enrichment
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