At the first NEGEM (New England iGEM) meetup, we began talking to the Northeastern iGEM team. After watching their presentation, we learned that they were interested in microbial electrolysis cells, wastewater treatment, and energy, and thought that they would be a good match for us. Their project seeks to improve the efficiency of a microbial electrolysis cell (MEC) by pairing the commonly used MFC/MEC strain Geobacter sulfurreducens with an engineered E. Coli that assists in exporting protons and removing oxygen from the media (since Geobacter sulfurreducens is an obligate anaerobic bacteria).
For our part of the collaboration, we assisted characterization of the Northeastern team’s novel part, BBa_K2182000, which encodes NADPH Oxidase. NADPH Oxidase, or the Nox protein, catalyzes the formation of water from NADPH and O2. In their system, the Nox protein maintains an anaerobic environment for the Geobacter sulfurreducens. After receiving their Nox part, we transformed it into BL21 E. Coli, also provided by the Northeastern team. They requested that we then histag purify the protein and perform a coomassie stain to check for the presence of the protein. Unfortunately, their protein did not appear on the coomassie stain. In our communications, we learned that they were also having difficulties histag purifying and visualizing the Nox protein. One reason they gave for this is that the protein was not under a strong promoter, and was being expressed at low levels in the cell.
For us, the Northeastern team further characterized our PETase and sfGFP parts. We gave them our parts BBa_K201004, BBa_K201005, BBa_K201007 and BBa_K201008 (see here for details) in the plasmid backbone pSB1A3. They expressed PETase-sfGFP in BL21, a different E. Coli strain than the one we used. They then visualized sfGFP fluorescence in a plate reader, comparing fluorescence. Their results are shown below: In this chart, our PETase-sfGFP fusion proteins are on average more fluorescent than the control. By collaborating to replicate each other’s results, including our replicating Northeastern’s difficulty with NOX, we made steps towards achieving more reliable data. In particular, by using the BL21 chassis, Northeastern demonstrated the Plastiback is adaptable to cellular contexts.
In addition to collaborating with the Northeastern iGEM team, we also completed a collaboration with Virginia iGEM by participating in their biocontainment survey. This is the sticker we received from them for collaboration: