Improvement to the DspB gene used by Team CMUQ of 2017
Team CMUQ of 2017 used the DspB gene in their project. Our team had found a new research done by the Wuhan University of Technology in March 2021 that also relates to the DspB. The research’s name was Magnetic Immobilization of Dispersin B with Activity in Degradation of Bacterial Biofilm. These two researches both approached DspB function in the same way but used them differently, as we were able to see how one segment of genes could be used to complete so many different works. In this section, I will explain how a previous gene used by an iGEM team was modified and applied to a different research.
Biofilms are formed by an extracellular polymeric matrix, composed of polysaccharides, lipids, and nucleic acids, that surrounds a group of bacteria. They are functioned to reduce the sensibility of the bacteria toward antibiotics. Biofilms are involved in over 65% of bacterial infections and could lead to very serious consequences when not responded correctly. Disperisin B (DspB), from the glycoside hydrolase family, is a catalyst to the degradation of biofilms. When a bacterial cell is released to the external environment to build new biofilms, DspB's function is to degrade the biofilm. Previous methods are usually through chemical and enzyme binding. The new approach used a physical method to make the degradation process more stable and controllable.
Magnetoreceptor (MagR), a fusion partner for the functional immobilization of proteins on a magnetic surface, was inserted into the C-terminus of DspB to form a recombinant protein DspB-MagR. This protein will be then purified by the Ni-NTA affinity chromatography and immobilized on the Fe3O4@SiO2 nanoparticles. The homogeneity of the protein after purification and immobilization was 95%, meaning that theoretically, the loading process did not alter the protein greatly.
The researchers carried out bioactivity tests on the loaded protein and unloaded protein to see the difference. For pH sensitivity, there wasn’t a big change after loading as the highest sensitivity is still at 6. For temperature, the highest activity state raised from 30°C to 37°C after loading. This supports that the loaded protein will be more suited for medical purposes since its highest activity state is at a temperature similar to the regular body temperature. It was also tested that through a long duration, the loaded protein still kept a higher activity state than the unloaded protein.
The degradation function of DspB-MagR, immobilized DspB-MagR and Fe3O4@SiO2 was tested on the biofilm of Staphylococcus aureus. Fe3O4@SiO2 showed no effect on detaching bacterial biofilms, DspB-MagR was able to remove 10% while the loaded DspB-MagR was able to remove 50%. The immobilized protein was also tested for biofilms of other bacteria like the Bacillus Cereus and Staphylococcus sp and showed a significant removal rate. These results proved that using Fe3O4@SiO2 to immobilize the DspB-MagR recombinant protein is an alternative method for biofilm removal.
