10.3.2018: Data Analyzation and New Sample

Rationale: Since a spot test and plaque assay were completed on Monday (10/3), it was necessary to obtain and examine results from those tests. However, since both tests showed negative results, it was necessary to discard the plates and begin the process of analyzing a new soil sample. Therefore, Soil Sample E was found and collected from Minglewood Bowl and metadata procedures were performed.

Data from Monday, October 1:

Both the spot test and plaque assay analyzations showed that no plaque had been caused by the samples derived from Soil Sample D. The only disruptions in the lawn growth of arthrobacter were caused by deformities and tears in the plate, and those deformities had been recorded prior to the completion of the test on the plate through dots of blue marker. However, it was also observed that control plates for both the spot test and plaque assay did not contain arthrobacter or any other form of contamination.

Top Row: Plaque assay, Spot Test

Bottom Row: Top Agar Controls

Procedure: Plates from 10/1/18 were analyzed. Soil was collected from a live oak in Minglewood Bowl near Brooks Residential Flats. Tree metadata form completed and submitted. 4mL of soil was placed in Falcon Tube. 8mL DI water was added to Falcon Tube along with 3 drops of soil dispersion liquid. Soil was shaken and vortexed for 30 seconds, then allowed to settle under fume hood to be left overnight. Added 4.15g of soil to a weigh boat (“HMB 10/3/2018”). Placed weigh boat under fume hood to be left overnight. Added roughly 10 drops of soil supernatant from Falcon Tube to pH tube. Filled the remainder of tube with DI water. Held pH paper in sample for 30 seconds to obtain a pH reading.

Observations:

• Soil sample was taken from an area without any grass covering the soil. Soil was still moist, and the sample was taken from approximately 2 inches below surface to avoid overly dry or caked mud.

Data from 10/3/2018:

• pH of sample was 6

Next Steps:

• The soil will need to be washed and prepared to test on Monday. Furthermore, the metadata procedures that were started today will also need to be observed on Monday, and the data will be collected then.

Conclusions:

• Since the plaque assay and spot test for Soil Sample D did not show any plaques, it was concluded that Soil Sample D did not have any phage present.
• As noted earlier, the control plates did not display any evidence of contamination that was prevalently seen in the majority of the samples before this one. This shows that the recent change in Top Agar and LB Broth likely replaced contaminated samples that were causing systematic contamination of samples throughout the class. Therefore, the conclusion can be tentatively drawn that the contamination was caused by old and contaminated LB Broth and Top Agar.