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Team:British Columbia/Project DspB
From 2010.igem.org
Introduction
Dispersin B (DspB) is an enzyme that degrades biofilms by catalyzing the hydrolysis of poly-ß-(1,6)-linked N-acetylglucosamine bonds. These bonds exist in the extracellular polymeric substance (EPS), which acts as a polysaccharide adhesin relevant to biofilm formation and integrity in Escherichia coli and Staphylococcus epidermidis. According to Lu and Collins (reference), DspB effectively cleaves these bonds and impedes biofilm formation. The DspB sub-team's goal was to isolate DspB from its natural host Actinobacillus actinomycetemcomitans and incorporate it into a phage to effectively eliminate Staphylococcus aureus biofilms.
Approach
We ordered Actinobacillus actinomycetemcomitans strain HK1651 genomic DNA from ATCC and designed two sets of primers to PCR the sequence for DspB off the genome:
Set (1) Primers with a histidine tag
Set (2) Primers without a histidine tag
The PCR with set (2) primers was successful and we created a standard biobrick part with the appropriate flanking restriction sites, EcoRI, XbaI, SpeI, PstI, on the required chloramphenicol resistant backbone (psb1c3).
In order to express the DspB protein in E. coli, we aimed to build the following construct:
We used the constitutive promoter (insert part number) with a ribosome binding site (insert part number)and relied on the terminator already present in the psb1c3 plasmid. The original plan was to isolate DspB using the histidine tag as well as lyse the cell to obtain crude lysate. However, since only the PCR with set (2) primers worked, we continued our experiments using crude lysate.
To characterize DspB's ability to degrade poly-ß-(1,6)-linked N-acetylglucosamine bonds, we performed SUBSTRATE assays.
Results & Discussion
Future directions include testing DspB's effect on a S. aureus biofilm, as well as incorporating DspB into the phage for exposure to S. aureus biofilms.
