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BSC242 Lab Exam1 Study Guide

by: Alexandra

BSC242 Lab Exam1 Study Guide BSC 242

Marketplace > University of Alabama - Tuscaloosa > Biology > BSC 242 > BSC242 Lab Exam1 Study Guide
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Lab Exam Study Guide for first exam. Includes table of vocab, pictures from lab manual and procedure steps.
Microbiology and Man
Daryl W. Lam
Study Guide
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This 8 page Study Guide was uploaded by Alexandra on Sunday February 21, 2016. The Study Guide belongs to BSC 242 at University of Alabama - Tuscaloosa taught by Daryl W. Lam in Winter 2016. Since its upload, it has received 101 views. For similar materials see Microbiology and Man in Biology at University of Alabama - Tuscaloosa.


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Date Created: 02/21/16
Vocab Culture A medium that contains living microbes Pure culture Culture containing a single species Aseptic Without contamination Mixed culture Microbial culture consisting of 2 or more species Colonies Groups of cells sufficiently isolated consisting only of the original cell type Free-living Miccroorganisms that do not reside on or in a specific plant or animal host Host Some microorganisms’ place of residence Nonpathenogenic Not known to cause disease Pathogens Known to cause disease Commensal Relationship in which organisms live on host but does not hurt or help Mutualistic 2 organisms exist in a beneficial relationship for both parties Opportunistic pathogens Capable of producing a disease state if introduced into a suitable part of the body Reservoir Any area where a microbe resides and serves as a potential source of infection Chromogen Colored molecule part of a stain (often a benzene derivative) Chromophore Part that gives the chromogen its color Auxochrome The charged portion of a chromogen, allows it to act as a dye through ionic or covalent bonds between the chromogen and the cell Exercises 1-5 Streak Plates always assume bacterial sample is mixed culture streak over surface of agar medium cell density decreases, leaving individual cells to grow into colonies Method: Quadrants  Zig-zig streaking 3-1 pg 125 Intro to Light Microscope 1-4 pg 25 Common Aseptic Transfers and Inoculation Methods never hold a tube by the cap hold inoculating loop or needle like a pencil heat the tube and the loop or needle before and after each use Types of media Broths: used to grow microbes when fresh cultures or large numbers of cells are required Agar Slants: used to grow stock cultures that can be maintained for several weeks Plated Media: used for obtaining isolation of species, differential testing, and quantifying bacterial densities 2-1 Ubiquity of Microorganisms “ubiquitous in nature” means it can be found just about everywhere 3-10 Bacterial Motility: Wet Mount and Hanging Drop Preparations Wet mount: made by placing specimen in a drop of water on slide and covering it with cover slide. Hanging drop: allows longer observation because it doesn’t dry out as quickly. Apply petroleum jelly around well of depression slide. Place drop of water in center of cover glass and add living microbes to water drop. Place depression slide over cover glass without disturbing drop. 3-4 Simple Stains Basic stains: (auxochrome becomes positively charged by picking up H ion or losing hydroxide ion) attracted to the negative charges on the surface of most bacterial cells, thus cells become colored Dyes used: methylene blue, crystal violet, safranin (we used methylene blue in lab) Procedure: 1. Place small drop of water on clean slide with inoculating loop 2. Aseptically add bacteria to water 3. Allow smear to dry, then heat fix it 4. Cover smear with methylene blue for 1 min 5. Rinse with water 6. Blot dry with bibulous paper 3-5 Negative Stains Negative stains: uses a dye solution in which the chromogen is acidic and carries negative charge. Negative charge on the bacterial surface repels chromogen so instead the background is stained. Dyes used: Nigrosin or eosin (we used nigrosin in lab) Procedure: 1. Place drop of acidic stain at 1 end of clean slide 2. Aseptically add organisms to drop 3. Draw a clean slide cover into the drop 4. Once drop flows across width of spreader slide, push spreader slide to other end 5. Allow to dry 3-6 Gram Stain Gram stain: differential stain in which a decolorization step occurs between application of 2 basic stains. Primary stain is crystal violet. Iodine is added as mordant to enhance crystal violet staining. Decolorization with alcohol. Gram-negative cells are decolorized (lose crystal violet stain). Gram-positive cells are not. Counterstain safranin colorizes gram-negative cells. Gram-positive appear purple, Gram- negative appear reddish-pink. Gram-negative cells have outer membrane and thinner peptidoglycan Alcohol makes wall more porous and incapable of retaining crystal violet-iodine complex Gram-positive cells have thicker peptidoglycan and trap the crystal violet-iodine complex Procedure: 1. Aseptically add organism to clean slide, allow dry, heat fix 2. Cover with crystal violet, let stand 1 min 3. Rinse with water 4. Cover with iodine, let stand for 1 min 5. Rinse with water 6. Drip ethanol over slide, ONLY 10 SECONDS 7. Rinse with water 8. Cover with safranin, let stand for 1 min 9. Rinse and blot dry Results from lab: E. Coli= gram negative S. epidermus= gram positive B. cereus= gram positive 3-7 Acid-Fast Stains Presence of mycolic acids in cell walls is basis for acid-fast differential stain. Mycolic acid resists decolorization. Cells are reddish-purple after carbolfuchsin stain. Decolorization with alcohol removes stain from acid- fast negative cells. Methylene blue counterstains acid-fast negative cells. 3-8 Capsule Stain capsules (composed of mucoid polysaccharides or polypeptides) repel most stains. Capsule staining stains around the cells. Congo red or nigrosin is used. A basic stain colors the cell proper. Capsule remains unstained appearing as a white halo between cell and background. 3-9 Endospore Stain endospore: dormant form of bacterium that allows survival of poor environment conditions. Spores are resistant to heat and chemicals because of outer keratin covering. Keratin resists staining so malachite green is forced into the spore by steaming the bacterial emulsion. Vegetative cells and spore mother cells are decolorized and counterstained with safranin. Cell Morphology Lab Results: Proteus: mobile bacteria M. luteus: not mobile Shapes: E. coli: rod shaped S. epidermus: round, glob B. cereus: rod shaped


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