On October 25th, we performed an organic extraction of our isolates. I had two isolates that I attempted extractions on. After letting the extraction vials dry, a residue was present which was weighed and subsequently resuspended in methanol. Not all of the residue dissolved, but 20 microliters of this resuspended methanol/extract solution was put on little circles to put on tester strains to see if they inhibited tester strains. If the tester strains were inhibited, it would mean we were successful in extracting an antibiotic from the bacteria!
We tested our extractions on two Gram positive and two Gram negative tester strains. Both of my isolates had inhibited at least one Gram positive and one Gram negative tester strain. To test extractions, I chose testers 1, 3, 4, and 5 (Staphylococcus epidermidis, Erwinia carotovura, Enterococcus raffinosus, and Actinetobacter baylyi, respectively). Testers 1 (Gram positive) and 5 (Gram negative) were previously inhibited by isolate number 11 and testers 3 (Gram negative) and 4 (Gram positive) were previously inhibited by isolate number 18.
Below are pictures of the results of testing the extracts on testers 3 and 4 (Erwinia carotovura and Enterococcus raffinosus). Extract from isolate number 18 inhibited both testers as seen by the clearing of growth of the tester bacteria around the 18 extract circle. This is interesting because I chose these two testers based on inhibition that I saw from isolate number 11, not isolate 18, but extract 18 showed inhibition while isolate 11 did not. However, extract 18 also inhibited testers 1 and 5 (Staphylococcus epidermidis and Actinetobacter baylyi), albeit not as robustly. Extract 11 did not show inhibition of any tester strains. The fact that extract 18 inhibited tester strains indicates that an antibiotic was successfully extracted!
Tester 3 – Erwinia carotovura – with organic extractions. The extraction from my isolate 18 shows a clearing of growth around it, indicating inhibition of the tester.
Tester 4 – Enterococcus raffinosus – with organic extractions. The extraction from my isolate 18 shows a small inhibition of tester growth around it.
