With BactWars, we build a biological tool that can target specific genes in multiresistant or pathogenic bacteria, and would kill or deactivate them.

To target specific genes we worked with the CRISPR-Cas9 system. By designing the sgRNA, we can target different genes. At first, we targeted the RFP with Cas9 by electroporating our plasmid.


Figure 1: [left] control producing RFP, [right] Transformed strain

After this experiment we knew our CRISPR-Cas9 system was operational.

For the transfer of genes, we worked with conjugative plasmids (pSW23T and pK18mob).

We tried at first, a conjugation without killing. We transferred our conjugative plasmid pK18mob containing the LacZ gene coding for the beta-galactosidase. So The receiver strain, that produces RFP, will then acquire this gene and will appear purple on Xgal media from producing RFP (red) and metabolizing Xgal (blue).


Figure 2: [Red] Receiver strain, [Blue] Donor strain, [purple] Conjugated Receiver strain

We know from now on that our conjugation is working. We can now combine the two tools.
Thus, our next step is to target the RFP gene with our conjugative plasmid containing Cas9.

Cross test 1: [left] overview, [center] close up conjugative donor strain with sgRNA targetting RFP (+), [left] close up conjugative donor strain without sgRNA targetting RFP(-).

We can see that the conjugation line is visible under the microscope and an effective difference between the control, without sgRNA, and the conjugative strain with the sgRNA.

The last step aim at targetting a resistance gene in the receiver strain.


Conjugation in plate test 1: [left] : Donor and recipient strain after conjugation. [right] : control and recipient strain after conjugation.

According to the petri dish on the left, no receiver strain was able to grow on antibiotic containing media after the conjugation. To confirm this result, the experiment should be repeated.
To visualize at the scale of a cell, the effect of the transfer of a mobilizable plasmid, containing Cas9 and its RNA anti RFP guide, by conjugation: we performed a 60-minute time lapse on a mixture containing the donor strain (S17-1 with pK18mob_CAS9_sgRNA anti RFP and pSB4C5_R0010_E0840 (GFP)) and the recipient strain (DH5a with pSB4A5_J04450 (RFP)).

Want to know more about our experiments? See our page Results