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Counting cells using the pour plate method

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Introduction

Unit 3: SCIENTIFIC INVESTIGATION ASSIGNMENT TITLE: INDIVIDUAL INVESTIGATION PLANNING TITLE: COUNTING CELLS USING THE POUR PLATE METHOD KEY EDITED WORK 1ST DRAFT INTRODUCTION: In the start of this assignment, I was told to choose one of seven other experiments to do. I chose the Counting cells using the pour plate method because I find it much easier than the other ones. In addition, I have had past experience therefore; it should be straightforward. I also have more knowledge of it than the other experiments. I will be testing the effects of various items on the growth of bacteria. I will investigate using the pour plate method in which I will be counting the cells of bacteria produced, of which are viable. The pour plate method can be used to establish the amount of microbes/mL or microbes/gram in a sample. It has the benefit of not have need of earlier arranged plate, and is usually used to examine bacterial contamination of foodstuffs. While using the pour plate method, a diluted specimen is pipetted in a sterile Petri plate, and next melted agar is tipped in and combined with the specimen. Using this technique permits for a bigger volume of the diluted specimen. This is normally in the choice of 0.1 - 1.0ml. This technique yields colonies, which produce colonies all over the agar, not only on the surface. ...read more.

Middle

Again, using aseptic technique, carefully pour cooled, but molten, sterile agar medium into each Petri dish. Swirl each Petri dish very carefully to ensure that the samples and the agar are evenly mixed. Gently move each dish in a figure of eight pattern, but do not allow the agar to spill over the edge of the dishes. Allow the agar to set, and then fasten each lid with 2 pieces of adhesive tape. Invert the dishes, and incubate at 30�C. After incubation, count the number of colonies present in a dish containing a suitable dilution. Calculate the number of viable cells present in 1.0cm3 of the original culture. As an alternative to pipetting a 1.0cm3 sample into each Petri dish and then adding molten medium, a 0.1cm3 sample may be transferred to a ready poured agar plate. The sample is then spread uniformly over the surface of the agar medium using an alcohol flammed glass spreader. 1. 2. 3. 4. Following a couple of days, various sorts of microbes grow as divided colonies. Cells from separate colonies could be picked up for a subculture. IMPLEMENTING This was a very quick process in which everything had to be complete straight after another. Therefore, measurements also should have been done quickly during the experiment straight away to put into whichever solution it may have been. My results have been recorded according to how much attempts I made. ...read more.

Conclusion

My replicate values are not very close together; therefore tell I should have done more replicates for accuracy. I think I may have made parallax errors when counting the cells. This means I may have miscounted the results or over counted them. This may have been because of my bad eyesight or due to distraction while counting. This could have been improved to accuracy if I counted each plate 3 times at least. So the correct amount of colonies in each plate would be certain and not doubted on. On the other hand, I could have used a different method to count the cells to make it easier for me, like using a counting meter. To achieve much accurate results I think, other than avoiding contamination, I could have changed around my method a little so it could have been done quicker or much accurately. For example, I could have just left the petri dishes in the incubator for a little longer or lesser period; I could have also used a different culture for counting. If I were to do the experiment again, I would repeat it more than just 3 times so my results can show more accuracy and I can identify where/when I went wrong. Furthermore, the next time I would limit the temperature to see if that would make a difference in allowing my results to be precise and I would also avoid causing any errors. ...read more.

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