28 November, 2003
Plating Our Samples
While yesterday was spent preparing the lab to process our soil samples, today we started working with our samples. To start, 100g of each soil sample was removed from the sample bag and placed into a sterile flask. If we sampled at twelve different locations and collected three samples at each location, how many flasks were needed? Sterile water was added to the soil, and the soil was then placed in a shaker. A portion of this soil solution will be plated directly on to the LB agar. We plated different concentrations of each soil solution on to 3 LB plates. Some plates were plated very concentrated, while others were diluted. Why would we want to dilute when plating? Rusty gave the 3 LB plates 10ul, 50ul or100ul of soil solution. If all plates were given a total of 100 microliters (ul) of solution, how much water (if any) did he add to each plate?
Before we can plate on to YPD agar, it must be concentrated. To do this, we transfer the soil solution into a falcon tube. This is then spun in a centrifuge, allowing a pellet to form at the bottom. The liquid on top is decanted and the pellet is resuspended in water. This solution is then transferred on to the YPD plate using a pipette. Three plates were given 100ul of solution and three plates were given 200ul of solution. Why would we want to plate multiple plates for each sample?
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