24 September 2018 ✷ Spot Test #3

Rationale: A spot test will be performed to test for the presence of phage from the third soil sample collected.

Procedure

• The workspace was cleaned with CiDecon and 70% ethanol
• A tube with enough plate mix for two tests was mixed (fourth column) and a control plate mix was made (column 2). The volumes and concentrations of their components can be seen below.

• component	volume (control)	concentration	volume (spot test)	concentration
  2X Top Agar	2.5 mL	1X	5 mL	1X
  LB Broth	2 mL	–	4 mL	–
  1M Calcium Chloride	23 µL	4.5 M	45 µL	4.5 M
  Arthro	0 mL	–	1.0 mL	–

• The plates were poured immediately and were allowed to set for 10 minutes.
• The enriched sample was filtered through a 22 micron syringe filter and stored in a microcentrifuge tube for later use. 5 µL of the filtered enriched sample was added to the designated space on the plate. 5 µL of phage buffer was added to the plate as a control, and 5 µL of the direct sample was added to the plate.
• The excess samples were stored in the refrigerator and the plates were placed in an incubator to sit until needed again.

observations, results, data

Previously, a test for percent sand, silt, and clay was performed for further metadata. 

The solid within the vial reached the 2 mL line. The lowest layer, sand, reached 0.25 mL, silt reached 0.5 mL (0.5-0.25=0.25 mL silt), and clay was the largest (2.0-0.5=1.5 mL).

% Sand = (0.25 mL)/2.0 mL * 100 = 12.5%

% Silt = (0.25 mL)/2.0 mL * 100 = 12.5%

% Clay = (1.5 mL)/2.0 mL * 100 = 75%

UPDATED: the control plate had contamination and the spot test was negative.

interpretations, conclusions, next steps

The positive control plate was also negative, indicating that there was an error with the test. It is likely that there was an issue with the “arthrobacter” used in the test because the results that should’ve been positive were negative. Thus, the same test will be repeated in the next lab period because results from Day 9 are not usable.