Team:Cornell/testing/notebook/wetlab/4

Daily Details:

September 1

Conjugating nah into Shewy: Due to the mysterious failings of our attempts to ligate the nah operon, Tina tried to start fresh by re-digesting the nah operon-containing plasmid and the oriT-containing backbone.

Synthetic River Media: Mark and Chie created synthetic river media based on information on the mineral content of the Athabasca River, and started overnight cultures of numerous strains to test how sodium lactate supplemented river water would grow the cells.

Site-directed mutagenesis: Swati transformed both her mutagenic PCR and her DpnI digest into DH5a after desalting on a membrane. She also ran both of the aforementioned samples on a gel without purifying, in order to check if either the digestion or purification steps were problematic. The gel was yet again blank, suggesting that the PCR itself was the problem.

September 2nd

Conjugating nah into Shewy: Tina tried ligating an older digestion of the nah operon into the oriT backbone using a molar ratio or 3:1 and 6:1 for nah:backbone. She then de-salted and transformed the ligations into conjugation strain WM3064. Tina then ran a gel of the digested nah operon-containing plasmid and the oriT-containing backbone and extracted the nah operon and oriT backbone bands.

Synthetic River Media: Mark set up a 96-well plate to test growth of the engineered strains in sodium lactate at varying concentrations, in synthetic river media.

Site-directed mutagenesis:The third transformation attempt yielded no colonies on the plate of DpnI-digested DNA, but three colonies on the PCR only plate, suggesting that these were just excess template. Nonetheless, Swati set up cultures to miniprep the following day. She also realized that she had been using a template that was 10x more concentrated than it was supposed to be. She proceeded to set up a fourth attempt at a mutagenic PCR, this time with the correct template concentration, primers for mutating a different cutsite than she had previously been attempting, and a higher annealing temperature.

September 3rd

Conjugating nah into Shewy: Tina extracted the nah operon digest and the oriT backbone from yesterday's gel. Tina and Dylan had an epiphany - we forgot to dephosphorylate the backbone! No wonder we kept seeing self-ligations! With a renewed spirit, Tina dephosphorylated the digested oriT backbone then started a sixteen hour 16 degrees Celsius ligation of the extracted digests. Tina tried nah to backbone ratios of 1:1, 3:1, and 6:1.

Synthetic River Media: Mark returned to the lab to discover that the growth assay went wrong. Numerous issues were identified with the original protocol to explain the failed result, and the protocol was changed.

Site-directed mutagenesis: Swati miniprepped the three suspicious PCR only colonies from the previous day, and digested with PstI to check for successful mutagenesis. She also did a DpnI digest and transformation of the PCR from the previous day. She ran the new PCR & DpnI digest, along with the PstI-digested minipreps of the three earlier colonies, on a gel, but to no avail. The new things showed nothing (again), and the digested minipreps produced completely incorrect bands.

September 4th

Conjugating nah into Shewy: Tina desalted yesterday's ligations then transformed them into our conjugation strain WM3064. WM3064 is E. coli that is auxotrophic for DAP (diaminopimelic acid epimerase).

Site-directed mutagenesis: The latest transformation did not work. Thus concludes this subproject!

September 5th

Conjugating nah into Shewy: Caleb and Tina checked the transformation plates - some colonies were visible on all three ligation ratio pltaes, but the colonies were so tiny we decided to wait another day before trying colony PCRs or starting liquid cultures.

September 6th

Conjugating nah into Shewy: Caleb decided the transformation colonies were large enough to colony PCR and start liquid cultures from. 13 total colony PCRs were performed on colonies from all three ligation mixtures and one positive control was run in parallel to be sure the PCR conditions were correct. Tina ran a gel of the the colony PCRs and the positive control. As can be seen in the gel pictures, colonies 3, 4, and 8 definitely had the nah operon and many other colonies had matching middle bands. These matching middle bands likely indicate some sort of mispriming. Colony 5 was clearly the product of an oriT backbone self-ligation. Caleb and Tina started 15 mL liquid cultures of apparently nah containing colonies 3, 4, and 8 and non-nah-containing colony 5 to Miniprep from tomorrow.

Fluorescence tests: This week started late as Claire was getting over a massive cold. However, with new vim and vigor and her trusty labmate Swati, they set forth to decide the details of how they will run fluorescence tests. To get ready for this, they set up cultures of JG700 and E. coli constitutively producing mRFP under the control of Anderson series promoters.

Daily Details:

September 9th

Conjugating nah into Shewy: Caleb checked the miniprep yields today - all but colony 5 had yields below 90 ug/uL. Colony 5 had a yield of over 500 ug/uL. Our hypothesis as to why the E. coli was growing so slowly was that the E. coli was stressed from having to express the many nah operon proteins. Evidence suuporting our hypothesis includes - colony 5 had a much larger colony, grew in liquid much faster, came out as lacking the nah operon, and yielded a lot more DNA from miniprepping than the colonies that supposedly had the nah operon.

Synthetic River Media: Again, the result of the growth assay was failure. This time, it appeared that the only issue was blanking, as the negative controls were reading higher than the inoculated samples. After some discussion with Dr. Archer, a better blanking method was determined, as well as the addition of longer mixing to the protocol.

September 10th

Fluorescence tests: We dephosphorylated SAL2 digested with SpeI and PstI for one hour, then heat killed at 65degC for 10min. We then ligated overnight with mRFP (also digested with SpeI and PstI) at 16degC in the thermocycler. However, JG700 and p41k didn’t grow, so we moved the plates to Riley Robb in the hopes that a more controlled incubator meant for Shewenella will help them thrive.

September 11th

Fluorescence tests: Swati transformed 2uL of SAL2_mRFP ligation mixture into WM3064. We also made cultures of JG700, WM3064, and p39k, p40k, and p41k in both JG700 and WM3064. We are hoping to run a plate with both strains on it to get an idea of whether we can see mRFP constitutively produced in JG700 (which is naturally red and may have some background signal), and compare that fluorescence to constitutively produced mRFP in WM3064. Once we have this control data we hope to be able to correlate fluorescence in JG700 with promoter strength.

September 12th

Conjugating nah into Shewy: Caleb and Tina started cultures of colony #3 from original transformation plate and cultures of JG700 + SAL and JG700. JG700 is Shewanella oneidensis with a ΔmtrB genotype. SAL refers to a plasmid with our reporter system that responds to the presence of salicylate by upregulating expression of mtrB.

Fluorescence tests: Cultures of JG700 p39k and p41k didn’t grow. We made new cultures with giant swabs of cells from the plates to see if the plates are dead, and subcultured from all the other cultures started yesterday. There are also two colonies on our SAL2_mRFP transformation plate, so we made 25mL cultures from these to see if we ligated successfully.

September 13th

Conjugating nah into Shewy: Caleb started liquid cultures of colonies #3 and #4 from the original transformation plate. Caleb also started a conjugation of JG700 + SAL with colony #3 and JG700 + colony #3. The conjugation was at room temperature on a DAP plate for 16.5 hours.

Fluorescence: Swati miniprepped the SAL2_mRFP cultures, and Claire set up a PCR to confirm whether SAL2_RFP was ligated successfully. Unfortunately it doesn’t look like the ligations worked, as neither band is ~4.5kb, which should be the length for SAL2 with mRFP. We think that the old digestions we are using may not be good, so we will start from scratch next time.

September 14th

Conjugating nah into Shewy: Caleb checked the liquid cultures from yesterday and noted there was no growth, as expected, due to the nah operon stressing the cells. Caleb streaked new plates from the conjugation - the LB agar plates had kanamycin and chloramphenicol for the JG700 + SAL and colony #3 conjugation and just chloramphenicol for the JG700 and colony #3 conjugation. The plasmid in the SAL strain confers kanamycin resistance and the plasmid in colony #3 with the nah operon confers chloramphenicol resistance. The strain of E. coli in colony #3 was auxotrophic for DAP, so the E. coli couldn't grow on the newly streaked plates.

Synthetic River Media: Cultures of only JG700 and Sal1 containing cells were started today, for another attempt at the growth assay.

September 15th

Running Reactors: Because maximal current production did not increase, Dylan took down reactors with working electrodes poised at 0.35V with respect the the Ag/AgCl reference electrode in order to free up potentiostat channels so that we can begin characterizing our arsenic reporter strains.