17 September 2018 ✷ Third Try’s a Charm?

Within Lab Group 6, two spot tests and one plaque assay were run, and all yielded negative results (see below). Thus, it was decided it was highly improbable that the sample was positive, so new soil was collected (again) in the same fashion as the previous time in order to try and locate a phage.

Lathan’s Questions

1. The sample Justin used likely had a higher phage concentration in it (a stronger titer).
2. 

Procedure

• As in the previous attempt at locating a phage, a soil sample was collected from a red oak outside of the Baylor Science Building (the difference from the last collection is the location of the tree).
• Soil was collected from 2 ft away from the base of the tree, but no specific data was collected other than photos of the tree. Circumference, crown diameter, and tree damage data were collected.  These data and images of the tree can be seen below.
• Upon returning to the lab, a small sample of the newly collected soil was set aside in a previously weighed weighboat to perform a test for percent water. It was left to dry under the fume hood until Wednesday’s lab period.
• The remaining soil was refrigerated until Wednesday.

Observations/results/data

• Circumference of tree: 102 cm; crown spread: 375 cm; some broken branches

• component	mass (g)
  empty weigh boat	2.41
  weigh boat + wet soil	6.66
  wet soil (6.66-weigh boat)	4.25
  dry soil + weigh boat	6.39
  dry soil (___-2.41)	3.98
  Water (wet soil – dry soil)	0.27
  % water (water/wet soil)	6.4% water

• Unlike the last tree, the most recent tree had more grass covering the base of the tree/roots. The correlation between this and phage presence is unknown, but hopefully it leads to the discovery of a phage.

Interpretations/conclusions/next steps

• The soil collected today will be enriched next time and then spot tested in order to hopefully isolate a phage. The percent mass test will be concluded and more metadata, including percent sand, silt, and clay will also be conducted.
• The soil collected today is significantly less sticky (less clay) than the last soil sample. Again, the correlation is not known at this time, but this may possibly be a better environment for phages to infect arthrobacter and yield a positive spot test for presence of phage.