Where did you obtain your soil sample?
I got my soil sample in the manure pile at the barn my aunt rides at, Graystone Stables. I tried to go to the older and farther back part of the pile, and I took my sample from a layer about two inches below the surface of the pile.
Why did you choose this location?
I figured that not many other people have searched through a manure pile, and going to an actively decomposing mix of hay, wood shavings, and horse poop would reveal more than taking a sample from already spread dirt. I went to the back to try to get at a point where the feces was already decomposed to avoid fresh ones. I noticed three distinct layers in the manure pile: a top layer of dry but still presumably nutrient rich stall products, a middle layer of moist, dark, and slightly warm stall products that I assume was actively decomposing, and a bottom layer of dry and crumbly hay and soil. I took my sample from the middle layer.
Do you expect a lot of isolates? Why or why not? Have your initial observations supported this?
Yes, I did. Not only did I know that the results of a manure pile can support a lot of growth, the soil was warm to the touch due to the decomposers (I washed my hands afterwards). My observations have definitely supported this because I have an uncountable number of colonies even on my 10^-3 dilution plate.
What media did you choose? What dilutions?
I selected LB and AC media because they were nutrient rich and I figured the bacteria in my soil sample would like that, and I chose 10% TSA because it would make a good representation of bacteria that didn’t thrive in rich environments. I also didn’t have many others to choose from. Due to a misunderstanding of dilution, I made 10^-1, 10^-2, and 10^-3. I also made a 10^0 dilution just to see what that would look like, and threw it away after realizing it wouldn’t give me much data.
Will you need to redo any?
Over the weekend, I noticed that my 10^-3 dilution plates had a ton of colonies, making it uncountable (or really difficult to count). On Tuesday, I made 2 spread plates at a 10^-4 dilution for each media I used. The plates are in the incubator right now and are growing.
How did your sample differ on the different media?
So far, I’ve noticed that there are more green and blue tinted bacteria colonies on the 10% TSA plates than on the other plates, but the colors could simply be more noticeable due to the whiter color of the media. The 10% TSA plate also had white/grey colonies with rhizoid arms on the border. There were a couple of colonies on the AC plate that appeared to tower over the rest of the bacteria, rising about 0.5 cm above the plate. The LB plate had more fuzzy colonies on it, and I noticed more brighter yellow colonies on the plate compared to AC.
I agree with you about expecting a lot of isolates from manure. It is so rich and I feel like it could produce quite a lot of interesting things. I found a lot of different colors in my less rich media as well, I wonder why that is? Did you find more growth on AC or LB? I found similar growth on both, but rather different types of growth. I found LB had a larger variety of colonies than AC. I think a great thing to try in your case would be further dilutions because you said even 10^-3 had too many to count. I saw that you are trying 10^-4, but maybe even try a 10^-5? I think that is very interesting that you had so much growth.