Yeast Lab

Purpose: The purpose is to demonstrate the contrast between the reproduction of a culture if yeast if all one type and one of a mixture. We are going to observe how much reproduction occurs in a sample of all a type, all alpha type, and a sample of a group with mixed typing. 

Introduction:

Cells communicate by sending and receiving signals that come from other places such as the environment or even other cells. To trigger these responses the signals have to cross the membrane by either crossing itself or using receptor proteins that are in the surface. Yeast are unicellular fungi. Not much is needed for them to survive except for reduced carbon, nitrogen, biotin and salts and trace elements. Yeast is anaerobic and go through alcoholic fermentation. They also reproduce both asexually and sexually. When they reproduce sexually they need an alpha and an "a type" yeast cell. They then will grow towards each other once they receive each others fermone. They then will turn into a zygote and eventually reproduce. In our mixed culture of A and Alpha type you will observe:

Shmoo:

Zygotes:

                                                                           Budding

                                                               Third Image is a single Zygote

Single and Budding Haploids:

                                                       Pink is Single and Blue is Budding

Asci:

Methods: In this lab, a-type and alpha-type yeast cells were used. Using three test tubes, one containing a-type, 2 ml of water, and liquid agar, then two more were made using alpha-type yeast and a mixture of the two. Each culture was observed under a microscope at different time intervals, and the haploids and budding haploids were counted for the solutions containing one type. For he mixed type, haploids, zygotes, and asci were counted. The cells were counted at intervals of thirty minutes, twenty four hours and forty eight hours. The various types of cells were observed, counted, and documented in three different fields of view per culture. 

 Data:

Graphs and Charts:

Discussion:

In our lab, we focused on two types of yeast. A type and alpha type. There were few differences seen between the two types, however, I noticed that the A type seemed to produce asexually a lot more than the alpha type did. Looking at our data this is also supported. Other than the sheer amount of the haploids we could see, very little else is different.

                                                         A Type Yeast at 48 Hours

                                                          Alpha Type Yeast at 48 Hours

 However, when we look at the mixed culture and our two separate cultures, we notice plenty of different things.

Mixed Culture at 48 hours

         Things formed in the mixed culture that we didn't see in the two isolated cultures. We observed not only single and budding haploid cells as we did in the isolated cultures, but we also saw shmoos, single and budding zygotes, and asci. These different things were the result of the mating occurring between the two types. As the time went on the yeast mated more and more producing more yeast molecules as can be seen in our data. They find each other by releasing pheromones that act as a signaling molecule in a G coupled protein receptor. This signal molecule allows the G coupled protein receptor to activate and produce the cellular response of growing towards each other and then mating. Since the two types of mating are very visually different it would be easy to conduct an experiment to determine which type was which if given a blank plate with no label. You could make two samples and add A type to one and Alpha type to another and which ever begins to form the different things such as shmoos, single zygotes etc. then you would know whether it was alpha or A. 

Conclusion:

The yeasts in the mixture had a lot of single haploids instead of having more asci. Even after 48 hours there wasn't that many asci. There was no set ratio that went on in the mixture. But there seemed to alway be more single haploids than anything. There weren't that many shmoos and budding zygotes. What we conclude is that when we looked at the yeast they had already gone through those phases. There were more single zygotes though. There was a difference between the alpha and a type yeast cells. A type produced asexually more than alpha did. Though at each observation we observed vastly more cells, the relative concentrations of each type of cell remained relatively constant.  

References 

http://learn.genetics.utah.edu/content/begin/cells/insidestory/

Also the lab background