Where did you obtain your soil sample? Why did you choose this location?
I obtained my soil from a flower bed located outside of my house. I chose this location partially out of convince, but also because it seemed like it would be a fairly rich soil, seeing as it was supporting a substantial amount of plant growth. To obtain my sample, I dug down about 1.5-2 inches, to collect some of the darker and wetter soil, and avoid some of the mulch on top.
Do you expect a lot of isolates? Why or why not?
Seeing as this is fairly rich soil, I was expecting a good amount of isolates to grow. The soil I chose was much more clay like, and was fairly wet since it had just rained. Since we had learned that clay-like soils tends to support the growth of more anaerobic microbes.
Have you initial observations supported this?
So far, I have observed a lot of growth on all of my plates. Each one of my plates produced growth, and there is a lot of diversity of color, shape, and size among the colonies on each plate!
What media did you choose? How did you sample differ on the different media? What dilutions?
Initially, I chose to use LB, AC, and R2A, my reasoning being that the richer and more nutrient dense medias would support the rich and presumed microbe dense soil. I chose to plate my 10^-2, 10^-3, and 10^-4 dilutions on each type of plate. After a few days of incubation, observations indicated that R2A grew the most diversity of microbes, however there was significant growth on the LB and AC plates as well. The 10^-2 plates of all three media were fairly overgrown, but still had some very interesting colonies. The 10^-3 plates were all very diverse and gave me the most useable colonies for my patch plates. The 10^-4 plates all had low amounts of growth, however this allowed my to obtain a definitive colony count, from which the cfu could be calculated.
Will you need to redo any?
I chose to redo all three of my 10^-3 plates to see if I got anymore interesting growth. I also decided to make two more 10^-3 plates, using the PDA and 10% TSA medias, since these are both minimal medias and my R2A plate had yielded the best results. I wanted to see if these media types would result in similar growth.
I like your thought process when selecting media. I had almost the exact opposite idea, that if a soil is rich with microbes a less rich growing medium would allow for a variety of microbes to grow without overgrowth. But I’m happy to see that all of your plates were successful! When you mentioned the amount of colony growth for all three of your plates, it seemed as if they all had similar growth. How did the cfus compare between the medias? Also, I’m curious to hear if the new PDA and 10% TSA plate grew more interesting colonies or had some colonies with similar morphologies as your other plates.
That’s interesting that you have such a diverse spread of colonies because my soil from the lawn in front of the Nott produced colonies with mostly the same shape and color. I had the same thought process when I was choosing my plates except I seemed to have the best growth on AC.
I think it was good that you dug down to get the soil, because it definitely allowed you to get to soil that was less disturbed than the topsoil; there were probably more remote microbes in that area that did not get disturbed often. I am somewhat surprised, though, that you had so much diversity, only because your soil was clay-like! I think it will be interesting, though, to see if the microbes that do end up growing in your soil would be more likely to produce Antibiotics, as their media is more restricted and competitive.