Question

1-5

ASSESSMENT Critical Thinking and Learning Outcomes Review 1. In the streak-plate technique, how are microorganisms diluted and spread out to form indi lluted and spread out to form individual colonies? 2. Which area of a streak plate will contain the greatest amount of growth? The least amount of growth Explain your answers 3. Does each discrete colony represent the growth of one cell? Explain your answer. Why can a single colony on a plate be used to start a pure culture? 4. Why can mannitol salt agar and EMB agar be described as both selective and differential media? 5. How can a streak plate become contaminated? 118 Basic Laboratory and Culture Techniques

Answer 1

Solution :

1 ) After successive streaking out in quadrants from the original streaks ,this technique spreads the microorganisms more with each quadrant

2 ) In streaking plate technique , the 1^st streaking area will have maximum growth but the colonies will be crowded together then the last quadrant streaked should have the least number of colonies , but they should be well separated and easily sampled.

3 ) The streak plate technique is used for the isolation into pure culture of the micro organisms from fixed population .

4 ) Particular organisms have growth in particular selective media favor, the differentiation for media between different groups of micro organisms . Mannitol salt agar and EMB do both of these select and differentiate between themselves.

5 ) The result of streak plate technique involves in formation of pure colonies from mixed sample. This was processed by streaking , a diluted gradient is established on the surface of the plate as cells are deposited on the agar surface.