Who/What: In this class, we are studying about bacteria and fungi. Because of that we have had labs that let us grow our own bacteria. In this lab, we will be able to grow some yeast. Before we got started on this lab, we first had to have a basic understanding of yeast and how they develop and colonize. Specifically for this lab, we made potato dextrose agar (PDA) and that is a type of growing medium for growing bacteria and fungi. How: For this lab, Jeff had a couple people peel some potatoes to make agar out of. To make the agar, I believe that Jeff heated up the potatoes with water (I'm not positive about this but that is what it looked like). Meanwhile everyone else continued on with the lab. We had to fill a pitcher with water then used a pipette to grab the amount of water we needed in each of our tubes. In each tube, there had to be 9.9 milliliters of water in each of them. We also labeled each tube with either 0.2, 0.4, and 0.6 because that would be the amount of the raw yeast left in each tube after we are through the experiment. Then we took 0.1 milliliters out from the potato agar that Jeff made and we put it into the 0.2 labeled tube. Then we vortexed the 0.2 tube and then took out 0.1 milliliters out of there and put that into the 0.4 tube. We then took out 0.1 milliliters out of the 0.4 tube and moved it to the 0.6 tube. We didn't have enough class time that day so everything else was set aside for the next day. On the next day, Jeff had put potato dextrose agar gel into our two plates. Then we vortexed the 0.6 tube and removed 0.1 milliliters out of it and into one of the plates, we also took out 0.2 milliliters out of the 0.6 tube and put it into the other plate. we had to spread out the liquid in the plates then we put the plates into the incubator. We had to insert the plates upside down in the incubator so the water that would come out of it would affect the growing of the yeast. We left the plate in the incubator for about 24 hours and then we took it out to count how many colonies of yeast have grown. Unfortunately, water got in our plates which messed up the growth of the colonies. Observations: When we first opened the plates, the one thing that stood out the most was the smell of the yeast plate. The smell wasn't that pleasant. It smelt like bread dough, I realized that it probably smelt like that because yeast is in bread and that it was we are smelling. When I took a whiff of the yeast plate, sometimes it would smell like coconut milk too and the yogurt we made before. The yeast plate looked like what melted cheese looked like on pizza. Since we believe that to much moisture got into the plate, the turn out wasn't great because we weren't able to count the CFU since they weren't clear. It also looked really moist, we didn't touch it so we weren't able to test this theory. Data:
No data could be received with the results we had. Analysis: We believe that our colonies couldn't grow correctly because water got in to the plates which caused distortion for the colonies to grow. Also, the gel in the plates wasn't evenly spread out so that caused the streaking of the colonies. The reason we believe that extra condensation got into our plates was the placement of the plates in the incubator and also because other people opened the incubator while our yeast was growing. If we were to try it again, we would want our plates to be left in the incubator, undisturbed or maybe we will pick a better place for our plate to sit in the incubator. 1. What is a colony and an what does it represent? A colony is a group of fungi or bacteria that are grown from a spore or cell on a culture medium. In our lab, the colonies are represented by the groups of yeast that have grown on our plates. 2. What conditions for growth have we provided for the yeast? For our lab, we put the bacteria into the incubator which was at a certain hot temperature, these conditions are what allows the yeast to grow. 3. If we wanted to check the rate of growth for yeast, what would be a possible experimental design? (e.g. What should we do differently? How many samples should we take?) I believe that if we wanted check on the rate of the growth, we can count the colonies that grew in each hour. By doing that we can find out how many are multiplying by the hour. If taking the plate out each hour will affect the yeast too much than I think we should make multiple plates and take a different one out each hour to see the difference. This last design might not work because each plate might react differently.
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