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Cards In This Set
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What is the differentiation between bacterial growth and increase in bacterial cell size?
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Bacterial growth is plural, referring to the amount of bacteria that are occupying a place An increase in bacterial cell size, is singular, referring to the growth of one cell.
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Why does streaking for isolation allow microbiologists to obtain a pure colony?
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Streaking will allow for cultures to become more and more "diluted" or separated, eventually creating pure colonies
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Process for streaking for isolation
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Separate dish into 4 quadrants. Quadrants 0, I, II, & III. Quadrant 0 where has the most and where you begin. Then streak from 0 into I and then streak to II and then III. Quadrant III should have the least and most isolated bacteria.
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Which quadrant in streaking will have confluent growth? Why?
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Quadrant O and I and will have confluent growth because the most amount of bacteria will be present in those quadrants.
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Which quadrant in streaking will have isolated colonies? Why?
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Quadrants II and III will have the isolated colonies because they have the least amount of bacteria in them.
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Usefulness of streaking for isolation technique to microbiologists
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1) Pure colonies can be used to start a large stock culture (subculture) of a single isolated bacteria. 2) Can be used to separate and isolate individual species of bacteria from mixed inoculum.
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What is the theoretical basis of streaking for Isolation?
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It is a method of dilution.
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Some critical issues to follow for streaking
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1) Start with small amount of inoculum from the stock culture. 2) Use the entire streaking surface of each quadrant. 3) Pick up new inoculums form the quadrant edges with a sterile loop. 4) Sterilize inoculation loop between transfers. 5) Proper aseptic tech should be followed.
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Time for 2 daughter cells to form from 1 mother cell
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About 20 minutes. Then the cells becom 4 and so on until after 50-72 generations in 24 hours.
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What is a pure culture?
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A broth or slant tube that only contains one type of bacteria
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What is confluent growth?
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A lawn of bacterial growth.
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What is a CFU?
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Colony Forming Unit. Individual isolated colony was started by one bacterial cell.
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In the streaking module what bacteria were used?
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Escherichia coli, Serratia marcescens, and Mixed.
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What is the purpose of pasteurization?
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It eliminates pathogens and decreases the overall number of bacteria. This increases shelf life. The FDA establish recommended times and temperatures.
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What are the basic FDA guidelines for milk safety?
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The FDA accepts 20,000 bacteria per mL of milk because the surviving bacteria are non pathogenic. Various temps and times are recommended by the FDA. (63C-30min) (72C-15sec) (89C-1sec) (90C-0.5sec) (94C-0.1sec) (96C-0.05sec) (100C-0.01sec)
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