MCRO 224 LAB MIDTERM 1 STUDY GUIDE.docx - MCRO 224 LAB...

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MCRO 224 LAB MIDTERM 1 STUDY GUIDE (Exercises 1-6, 10 &11) NEED TO KNOW CONTROLS: FULL GENUS/SPECIES CELL MORPHOLOGIES/ARRANGMENTS RESULTS (GRAM +/-) PURPOSE FOR EXAMS/PRACITCAL Exercise 1 o Exercise 1A: Bright field microscopy to view cells Image from light that is transmitted through a specimen and utilizes a compound light microscope Condenser: part of a compound light microscope that concentrates the light onto the specimen Parfocal: microscope image should reamin in focus despite changes in magnification of objective lenses Total magnification: magnification from objective lenses’ magnification from ocular lenses Ocular lenses: 10X & ocular lenses: 40X o Total magnification=400X Resolution: the clarity of an image Limit of resolution: the length of 2 points must be away from each other in order to be viewed as separate (light microscopy limit of resolution is 0.2 µm) Rheostat: dial that controls the intensity of the light Numerical aperture: a measure of a lenses ability to capture light coming from the specimen and use it to make the image (indicates the resolving power of the lens) o Exercise 1B: Measure cells Ocular micrometer: ruler inside the microscope eyepiece Ocular micrometer needs to be calibrated for each objective 10X= each o.u. ~10 µm 40X= each o.u. ~2.5 µm 100X= each o.u. ~1 µm Stage micrometer: used to calibrate the ocular micrometer Exercise 2: Environmental Sampling o Purpose: Identifying the 5 main categories of culture medium used in culturing o Culturing: growing organisms on media under controlled lab conditions o Five main categories of culture medium:
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1. Chemically Defined Medium ( Synthetic ) Known amounts of pure chemicals Used to grow specific kinds of organisms 2. Chemically undefined medium ( Complex ) o TSA: Trypticase soy agar; complex rich medium Exact component not known o Variation b/w batches Contains crude digests of plant/animal materials Used to grow different kinds of cultures 3. Selective medium Allows certain microbes to grow while inhibits others Additional components are supplemented for inhibition 4. Differential medium Contains ingredients that make bacterial colonies with certain characteristics appear different from others that are growing 5. Enrichment medium Simple to complex Designed to increase number of desired organisms to detectable levels Exercise 3: Cultivation techniques o Aseptic Technique Critical for cultivating—maintains purity of cultures Use flames (Bunsen burners) to sterilize Loops, mouths of tubes, etc. EVERYTHING is contaminated unless sterilized (this includes you, and even your air!) o Broth culture Most useful for large quantities Immediate use Healthy cultures o Slant culture Stored purified cultures Maintain for longer periods of time Weeks or months o Streak plate Extremely useful for isolating pure samples Mixed or pure cultures Useful for identification Colony morphologies
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