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BIOL125_Ch3 Lecture Notes

BIOL125_Ch3 Lecture Notes - BIOL 125(Microbiology Lecture...

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BIOL 125 (Microbiology) Lecture Notes Chapter 3: Methods For Studying Microorganisms 1. PROBLEMS ASSOCIATED WITH STUDYING MICROORGANISMS a. They are very small; hence, microscopes were developed. b. Live in complex associations with several different microorganisms. As a result, you need to isolate them in the pure form to study them individually. c. Need large quantities to study them. 2. CULTURING MICROBES a. Inoculation – introduction of a sample into a container of media to produce a microbial culture that can be seen with the naked eye. i. Requirements to grow: nutrients and a sterile environment (and equipment). The artificial growth media is prepared under sterile conditions. ii. Culture – macroscopic growth of microorganisms on the growth media (ex. petriplate – colony; broth – turbidity). b. Isolation – separating one species from another. i. Microbes are isolated into a pure colony using morphological differences that are visible (ex. color, shape). After isolation, it is subcultured to make sure that it is a pure colony. ii. Colony – a group of microorganisms arising from a single cell. It consists of one species. iii. I solation techniques include streak plate technique, pour plate technique, and spread plate technique. 1) Streak Plate Technique – A small amount of cells are inoculated on a growth media in a petriplate using an inoculation loop (will be tested on this technique in first practicum). 2) Pour Plate (Loop Dilution) Technique – Specimen is inoculated and serially diluted in a semi-liquid broth, causing the number of microorganisms to decrease in concentration after each dilution. 3) Spread Plate Technique – Specimen is diluted, and using a pipette, place onto a petriplate containing nutrient media. c. Incubation – maintain them under conditions that allow them to grow. i. Incubator – a temperature-controlled chamber set at appropriate temperature and at atmospheric pressure. ii. Time of incubation varies, depending on the microorganism (for bacteria, generally 20-40 ° C). d. Inspection – evaluation of pure cultures periodically to make sure they are pure. i. During inspection, grown is observed (macroscopic and microscopic). 1) Growth in liquid media make the media turbid. File: 5ee97f94f40a3e06a85de909c7e1725fe4f7e520.doc Updated 8/14/09
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Lecture Notes Chapter 3 Page 2 2) Growth on solid media appears as a colony. a) Pure Culture – grows only a single known species of microorganism. b) Mixed Culture – has two or more identified species of microorganisms. c) Contaminated Culture – a pure or mixed culture that has unwanted microbes growing. 3) Maintaining pure cultures is important to study them. Techniques to do this include: aseptic techniques; flaming; alcohol treatment; sterile equipment and media. e. Identification – characterize them using morphology, biochemistry, and genetics.
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BIOL125_Ch3 Lecture Notes - BIOL 125(Microbiology Lecture...

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