Team:Macquarie Australia/Results

Aim

We designed and ordered the gBlocks for 4 genes, which encoded for proteins involved in hydrogen production (FDX, FNR, Hyd1, HydEF, HydG) from Chlamydomonas reinhardtii.
Improved gBlock hydG which demonstrated a loss of functionality (2016) due to a point mutation.
Wanted the gBlocks to be inserted into one composite part (known as the Hydrogen Producing Gene Cluster) and transformed into Escherichia coli with lac promoters and chloramphenicol resistance.

Summarised Results:

Improvement of previous part, hydG, to fix point mutation and provide functionality.
Construction and sequence confirmation of composite parts: fer/FNR/hyd1, hydEFG, and Hydrogen Gas Producing Gene Cluster
SDS-PAGE and enzymatic assay of induced protein expression of ferredoxin and ferredoxin reductase.
Successful assembly of composite part - HGPGC in the following order: fer-FNR-hyd1-hydEFG.
Successful production of Hydrogen gas.
Awarded a Gold Medal.
Awarded Best Energy Project 2017.

Results

Summary of parts

All composite parts underwent single (EcoRI) and double (EcoRI with PstI) digests followed by agarose gel (1%) electrophoresis to summarise and validate the successful construction of the parts comprising the Hydrogen Gene Producing Gene Cluster (HGPGC) (see Figure 1). All parts are also sequenced confirmed.

1. Assembly - FDX/FNR/hyd1, electron transporters to power a hydrogenase

This biobrick was created to ligate a ferredoxin (FDX) and ferredoxin reductase (FNR), an electron transporter from NADP⁺ reduction, to a hydrogenase native in C. reinhardtii. The ferredoxin donates electrons to the hydrogenase for the production of hydrogen gas. Standard assembly of verified biobricks FDX/FNR and hyd1 was performed in a CAM backbone (see Notebook, Weeks 7, 8). The biobricks FDX/FNR and hyd1 were successfully ligated together (Figure 1) and sequencing results confirmed this.

2. Assembly – hydEFG, hydrogenase maturation enzymes

The hydG biobrick was constructed by the 2016 Macquarie iGEM, however it was found to have a 1bp mutation which appeared to cause a loss of functionality. This year we have corrected this mutation and following biobrick creation with transformation into competent DH5α cells, the sequenced results prove we have a functioning maturation enzyme. This biobrick was ligated with biobrick hydEF to assist in the formation of the H-cluster in the Hydrogenase.

3. Assembly - Hydrogen gas producing gene cluster

With sequencing of the biobricks FDX/FNR-hyd1 and hydEFG confirmed, all that remained was a final assembly. The Hydrogen Gas Producing Gene Cluster plasmid is a composite part; the total construct of genes FDX/FNR/hyd1/hydEFG (see Figure 1). All promoters are inducible lac promoters with a -35 and -10 consensus sequences of TTTACA and TATGTT respectively. The ribosome binding sites had a sequence of aagaagg following the promoter positioning.

The fer genes are a ferredoxin (FDX) and ferredoxin reductase (FNR) involved in the transportation of electrons which are passed to hyd1 (Hydrogenase). The hydEFG genes act as maturation enzymes that aid hydrogenase activation, so that following IPTG induction, when under anaerobic conditions, the gene cluster will begin to produce hydrogen gas.

Figure 1. Agarose gel (1%) electrophoresis of single (EcoRI) and double (EcoRI with PstI) digests of parts.
Left: Lane 1 contains a 1kb ladder. Lanes 2 and 3 show single (~10,700 bp) and double (~8700 bp with ~2000 bp) digests respectively of the composite Hydrogen Gas Producing Gene Cluster plasmid (HGPGC). Lanes 4 and 5 show single (~7400 bp) and double (faint ~5400 bp with ~2000 bp) digests of hydEFG. Lanes 6 and 7 show single (~5400 bp) and double digests (~3400 bp with ~2000 bp) of fer/hyd1.
Right: Lane 1 contains a 1kb ladder. Lanes 2 and 3 show double digests (~1900 bp with ~2000 bp) and single digest (~3900 bp) of hydG.
These gels validate all constructs of the Hydrogen Gas Producing Gene Cluster composite part.

For more information on our validation, go here.