Assembly Plasmids
Parts of an Assembly Plasmid
Assembly plasmids contain an antibiotic resistance gene, origin of replication, origin of transfer, barcode sequence, and a 1-5 bridge part, which contains a colored reporter protein coding sequence. The plasmids are made from 5 different part plasmids: a 1-5 bridge connector and part plasmids 6-8b, using a single BsaI golden gate reaction. The same promoters, terminators, and origins of transfer are used within all assemblies. Each 1-5 bridge connector has a different reporter protein coding sequence making it easy to determine which plasmid each colony contains. Each plasmid also contains a unique Barcode, that is paired to a specific origin of replication. This design eliminates as many variables as possible, allowing the origin of replication to be the single largest factor determining whether the bacteria sustain and express the plasmid.
We currently have 8 completed assembly plasmids and continue to make more. Table 1 shows the completed assemblies along with which reporter gene, antibiotic resistance gene, origin of replication, and barcode is on the plasmid. All assemblies have the same origin of transfer, assembly connectors, promoter/RBS, and terminator.
p15A Assembly Plasmid
Our lab has created a total of eight assembly plasmids and are constantly working to add more to the kit. Eventually each 1-5 bridge connector, with an assigned chromoprotein reporter and barcode, will be assigned to a specific origin of replication. We currently have created three 1-5 bridge connectors with the GFP, RCP, and E2C reporters. The plate shown below demonstrates in E. coli cells what a successful assembly plasmid transformation looks like with a GFP reporter. While a successfully created part-plasmid does not exhibit any chromoprotein, assembly plasmids do exhibit the chromoprotein from the 1-5 bridge connector part.
In figure 2, assembly BHR904 has the 1-5 bridge connector with GFP (901.1) as you can see the single green fluorescent colony on a plate of other non-fluorescent colonies.These non-fluorescent colonies did not pick up the BHR904 plasmid but still have CAM resistance possibly from picking up other undigested part plasmids (all part plasmids have CAM resistance). It is normal to only see a few colony that are transformed with the assembly plasmid and express the chromoprotein
Shuttle Vector Assembly
Broad Host Range assemblies encoding a shuttle vector, pAMBI, were assembled using standard Golden Gate assembly protocols. BHR 925 (E2-Crimson + pAMBI Origin + CRB resistance), 920 (E2-Crimson + pAMBI Origin + KAN resistance), and 922 produced darker, bluish colonies under visible light. When viewed under a UV light, the colonies were red, indicating the successful expression of E2-Crimson
Minpreps of the BHR 922 assemby, which produced colonies but was shown to be only the E2-Crimson 1 – 5 bridge, was re-transformed into E. coli along with BHR 920 and BHR 925 to better view expression