“Do you expect a lot of isolates? Why or why not? Have your initial observations supported this?”
I didn’t really know what to expect when I collected the soil. It was close to the compost, which likely has a lot of microbes. However, the soil under the tree is rather protected. My initial observations showed less robust growth than I expected. My CFU was only 4.5-1.2 10^6 colonies / gram of soil.
When I let the plates grow for several days there was more growth, but there appear to be only a few different types of colonies.
“What media did you choose? What dilutions? Will you need to redo any? How did you sample differ on the different media?”
I decided to use 2 “rich” medias-LB and AC, and 1 “less rich” media-PDA. I chose the 2 rich medias because I was unsure how rich my soil sample was in microbes. I chose the PDA because it was mentioned in class lecture that several microbes that produce antibiotics like to grow on PDA. I originally plated 10^0,1, and 2 dilutions of media in PBS. I had to redo a few because I waited 5 days (I was away over the weekend) to look at my plates, and they were all too dense to collect a CFU and patch colonies. I then plated more of the 10^2 and 10^3 dilutions on all 3 types of media, so individual colonies were more identifiable. My PDA plates were also covered in a thick slime, which was potentially hazardous so I threw it away. The AC and LB plates showed similar growth–mostly small, white, gray, and yellow, round colonies.
(P.S.) if I accidentally replied to people my apologies! it took me a few tries to get this is the right spot
Love that we both chose samples underneath a tree on a rainy day. My samples showed too many colonies to count in the first round as well – but my replated dilutions were countable now – hovering around 10*10^6 CFUs per gram – with LB having lower CFUs than R2A or PDA! Like you said, I got mold on my PDA’s too…probably because we both got our samples under a tree. My replated PDA with 10^-3 dilution still shows some mold growing though not as much. My R2A and LB plates resembled what sounds like your LB plate – mostly small, white, gray, and yellow, round colonies. I also replated all of mine at 10^-3 and more countable and diverse colonies. Were you able to patch from PDA? My PDA patch plate became overgrown with fuzzy mold… so watch out for that!