Friday, December 20, 2013

Cell Communication Lab: Yeast Cells

For this lab, we focused on cellular communication. Cell communication happens between unicellular organisms and inside multicellular organisms. To communicate with their neighbors, cells secrete chemicals to other cells to "switch on" the cell. Organisms communicate via chemical signals to coordinate functions and to respond to the stimuli in their environment. A molecular signal reaches it receptor on the cell, and a series of reactions occur. Cells can communicate by direct contact, local signaling, or long-distance signaling. Yeast cells are unicellular fungi, that can reproduce sexually or asexually. Yeast can be cultured on solid or liquid media. If cells are streaked over a solid medium, they grow in colonies on top of one another while yeast cells that are mixed into a liquid medium grow evenly throughout it. During this experiment we observed yeast cells and their responses in both solid and liquid mediums.

The purpose of this lab was to determine how cells, like yeast cells, communicate with one another. Yeast cells do not have legs and cannot swim to other cells to mate with them, so we wanted to see exactly how that would happen. We were also testing to see how much the yeast cells would reproduce during the time increments we set for them. We counted the different types of cells after 0 minutes, 24 hours, 24 hours and 30 minutes, and 48 hours. The independent variable is the amount of time that the cells had to reproduce. The dependent variable is the percent of the total of the cell that a certain type of cell was, like a single haploid cell. 

First, we labeled each agar plate and corresponding culture tubes "a-type," "alpha-type," and "mixed type". We added about 2ml of water using a pipet to each culture, then used a toothpick swab to pick up a colony from each plate (using a different pick each time). Following this, our lab group observed each yeast Petri dish under the microscope: once at the start, after 24 hours, 24 hours and 30 minutes, and again after 48. We counted to the best of our abilities the cells we observed under the microscope. 
During this lab we were instructed to practice the "sterile technique," meaning handling tools without contamination. By doing so, we did not allow our tools of this lab to touch anywhere that's not a "clean zone". We never used a pipet, swab, or spreader more than one time. If we did, who knows what kind of bacterial growth we would see. We were sure not to let our skin touch the yeast either. 


          Alpha culture after 24 hours 

                         Mixed culture after 48 hours 
            Alpha type after zero minutes 

In this experiment we wanted to test the communication in different strands of yeast. We tested  A type, Alpha type, and mixed type. The  key difference between these types are the different genes in Alpha and A type.. These A and alpha type can combine to make a mixed cell via single transduction pathway. The mixed cells are a combination of A type and Alpha type, these cells can become a haploid, budding haploid, zygote, budding zygote, or a shmoo. A haploid is a single cell. A budding haploid is a single cell with a growth on the side. A zygote is two cells that look like an infinity sign. The budding zygote is 2 cells that are like infinity signs with a growth that looks like a dot. A schmoo looks like a pear, and it the two cells combining together. The mixed type can have shmoos, both haploids, and both zygotes. The A factor and alpha type only have budding haploids and haploids, this is because the A type and Alpha type had nothing to mate with. Single transduction pathways use several steps to produce a cellular response.  The yeast cells use G- protein receptors system to mate. G protein receptors are also single transduction pathway. G proteins consist of a signaling molecule, a g protein, G protein coupled receptors and an enzyme.  The signaling comes to bind to the G protein on the extracellular side. This causes the G protein coupled receptor to change shape on the cytoplasmic side. When the receptor changes shapes a G protein to bind to it. This activates G protein to make a GTP and get ride of the GDP the protein currently was holding. Then the active G protein combines with the enzyme to active the enzyme, to trigger a cellular response. Once the enzyme is activated, the G protein acts like a GTPase enzyme. GTPase use hydrolysis to get ride of the third phosphate. To make the protein inactive and ready for reuse. This yeast cells are able to do this by commicating with secret messages. These secret messages are called pherenomes. In the graphs you can see that the for the first 30 minutes on the A type of Alpha type the number were very high at first but as time progressed to 24 hours the number of haploid and budding haploid started to decreases. This happened because the cells had no one to mate to so they started to die off as time went on.  For the mixed type the numbers increased as time went on. This is because the Alpha and A type were able to mate, and create more yeast cells. 

This experiment can be fixed by wearing gloves. Maybe if we wore gloves it could decrease on contamination. The lab was very sterile but if we had gloves we could make it even more  sterile. This could help prevent other types of bacteria from growing. Also, our lab group was not very accurate when we were counting the different types of cells. The next time we do this lab, we would work on counting them more accurately to get better data. 

Cell communication is required in many different biological functions (sexual reproduction included). In this lab, we observed cells signaling each other in two strains of the yeast Saccharimyces cerevisiae. In the A and Alpha type cultures, we examined the life cycle and mating routines in the yeast and in the mixed cultures, tons of bacteria were living throughout. 

1 comment:

  1. Great Job! Very informative and well put together. next time I would see if you could "zoom" in on the pictures a little more. I know it was tough to just get the picture.

    Nice Job!