Where did you obtain your soil sample?Why did you choose this location?
I collected my soil sample between the pyramid and the bank of the Hans Groot Kill. I dug about an inch down, and tried to avoid the grass and roots that were in the soil. I chose this location for two reasons. The first being out of sheer convenience. The location was right on the way to class, so I was able to just wake up 15 min early and be set with collecting my sample. I also chose this location because I thought there would be some interesting bacteria found there due to the activities that happen on and near the pyramid.
Do you expect a lot of isolates? Why or why not? Have you initial observations supported this?
I expected to get a fair amount of isolates due to the location and soil type. The soil was clay-like and as mentioned in class this tends to support more anaerobic microbes. However, since my sample was collected from the top layer of soil, I figured there would still be a good amount of aerobic microbes. I also thought due to the highly trafficked area (and activities that go on there), there would be a lot of different microbes. Also the sample was collected near the creek, and after hearing how there’s lots of stuff in the water during class, I again thought there would be plenty of microbes in my sample. Initial results have proven that my sample has a good amount of microbes in it, yet the diversity is lacking (the majority of colonies are off-white and round with very similar morphologies).
What media did you choose? What dilutions? Will you need to redo any? How did your sample differ on the different media?
I chose LB, R2A, and PDA media. Since I thought there would be lots of microbes in my sample I chose to do two of the less rich media and only the LB rich media. For similar reasons, I used the higher dilutions of 10^-1 through 10^-3 (numbering system in book) for each of the medias. Interestingly, the R2A had very rapid growth of both colonies and mycoides, and needed to be diluted to 10^-4 to obtain accurate counts. As for the different media, it mostly affected the diversity of the colonies rather than the number of colonies. For instance, the R2A tended to have mostly white colonies that pretty much looked the same and mycoides, whereas the PDA had many different morphologies and colors. LB samples tended to be somewhere in the middle regarding morphologies- there were many similar ones, but there were also some unusual/unique looking ones.
It’s interesting to me that you took soil from near the pyramid (given what we all know goes on at the pyramid) and that you ended up with good growth on the R2A plates. I wonder if there could be a connection there? Granted, I’m not really interested in testing that connection, but it’s something to think about as you go through the next steps!
My real question is: did you wear gloves to pick up your soil or did you decide to “play” with it?
I find your results quite interesting as I also obtained similar results. In particular, my PDA plates also contained diverse colonies that differed very significantly in morphology and color. My LB plates also had a lot of colonies, but they didn’t vary that much except for one LB plate that had a numerous amount of colonies that were quite similar to each other but for few colonies that were definitely particular and strange. I wonder if I used R2A plates, I would get comparable results; and I obtained my soil sample from a completely different location.
On my LB and AC plates I didn’t have that much diversity, but my PDA plates did, too. From reading other posts, PDA seems to be one of the better media for getting the most diverse colonies to grow.