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Microbiology Lab Midterm Review Wednesday, October 08, 2008 10:41 PM Experiment 1- Media Preparation and Sterilization 1. Solid medium contains agar (from red algae) Melts @ 100C, Solidifies @ 40-42C 2. Types Plate - isolation Slant - maintenance Broth - liquid Deep anaerobic growth 3. Complex medium composed of digests of chemically undefined substances such as yeast and meat extracts 4. Defined medium medium whose precise chemical composition is known Sterilization : killing or removal of all living organisms 5. Autoclave: 121C (for media, glass) 6. Dry heat: flaming, hot air (for loops, glass) 7. Filtration: for heat-sensitive liquids (antibiotics) 8. Radiation: UV, gamma rays (for surfaces) 9. Cold sterilization: ethylene oxide (for heat-sensitive materials) 10. Experiment 2- Culturing Microorganisms from the environment 1. Minority of microorganisms are pathogenic- disease causing agent 2. Nosocomial means hospital-acquired Purpose : This experiment will demonstrate the ubiquitous nature of microorganisms. Materials needed: 3. 1 Trypticase Soy (TS) broth 4. 2 TS agar plates 5. 2 sterile swabs Experiment 3- Hand Washing 6. Resident (normal) microbiota/flora occur naturally on or in body 7. Transient flora temporary on body, cant grow on skin because skin is too dry and acidic 8. Nosocomial infection hospital-acquired infection 9. Infectious dose number of microorganisms required to establish an infection Purpose : This experiment will evaluate effectiveness of different soaps & hand washing times. Experiment 4- Colony Morphology 10. colony - a group of genetically identical bacteria, arising from a single cell on an agar plate 11. colony morphology - colony characteristics; see next slide 12. contaminant - an unwanted organism which has been accidentally introduced into the culture 13. Purpose : To observe the colony morphology of several organisms and become familiar with the terms used to describe colony morphology 14. Organism Color Colony shape Margin shape Elevation Optical properties Surface charact-eristic Escherichia coli Beige Round Smooth Flat/ convex translucent Shiny Bacillus cereus White Rhizoid Lobate/ filament Flat opaque Dull Micrococcus luteus Yellow Round Smooth Convex opaque Shiny Saccharomyces cerevisiae White Round Smooth Convex/ umbonate opaque Shiny Streptomyces coelicolor Purple/ white Irregular/ round Smooth/ lobate Flat opaque Dull Serratia marcescens red round smooth convex opaque shiny Experiment 5- Asceptic Technique See p. 20-21 for proper technique Experiment 6- Pure Culture 15. Pure culture - one that contains only one kind of microorganism; an isolated colony is one example of this 16. Streak plate - technique for diluting bacteria on agar plates; can be used to isolate individual bacteria from a mixture Purpose : To isolate a pure culture (in the form of an isolated colony) from a mixed culture using the dilution technique known as streak plating 17. Important to use proper aseptic technique in lab to avoid contaminants17.... View Full Document

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