1. What is one advantage of utilizing the pour plate technique over the streak plate technique ?
2. Why must the agar pours be cooled to 45C before use in the pour plate technique?
3. Explain the consequences if a group removed all the agar pours from the water bath at one time and allowed them to sit on the bench for several minutes before using them.
4. Why can the agar pour tubes be rinsed in the sink after the agar is transferred to the Petri plate ? Could you rinse the tubes if the bacteria had been pipetted into the agar pour tubes rather than in the plates? Explain.
5. What would be the result if a student dipped his / her loop in the stock culture during inoculations of each quadrant ? Explain .
part B
1. The introduction stated that microbes are mechanically separated or diluted over the surface of the medium . How is this accomplished ?
2. Go to https://commons.wikimedia.org/wiki/File:MacConkey_agar_with_LF_and_LF_colonies . . Which side of the plate (left or right) indicates an organism capable of fermenting lactose Explain your answer fully .
3. What would be the result if a student dipped his / her loop in the stock culture during inoculations of each quadrant ? Explain .
4. Compare the three methods for achieving isolated colonies and list the advantages and disadvantages of each.
Answer: THERE ARE THREE TYPES OF CULTURE METHODS
1. POUR PLATE TECHNIQUE
2. STREAK PLATE TECHNIQUE
3. SPREAD PLATE TECHNIQUE
1.1 POUR PLATE TECHNIQUE : This is a serial dilution method , when the amount of inoculum is transferred from the stock culture to consecutive test tubes containing distilled water. test tubes are made at different dilutions and the last 2-3 dilution pour in the petri plates. In this method colonies appear throughout the depth and surface of medium. It is also used to estimate viable count, recommended method for quantitative urine cultures.
2.2 STREAK PLATE TECHNIQUE : This is a surface streaking method, when a loop dipped into the culture media and streak back and forth over the agar surface on petri plate. we should not use force while streaking it would break the agar and make the gaps inbetween. In this method the colonies found on the surface of the agar medium. Isolated colonies then can be pick and be studied and sub culture cab be done. The most important thing while streaking is that we must sterilize the loop before streaking this will avoid the contamination.
3.3 SPREAD PLATE TECHNIQUE: This is a culture spreading method, in which the petri plate first made with required agar and leave for solidifying , and then take a loop of culture from stock and add (mix) in the test tube containing lb broth. after mixing throughly and gently and drop the some amount of broth containing sample on the agar petri plate. and then immediately with the help of spreader , spread the drop all around the petri plate. and allow to incubate. The colonies appear on the surface of the petri plate.
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