Proof of Concept

Bacteriocins – They work!

In the project we designed biobricks, which contain the genes encoding a single bacteriocin or a hybrid bacteriocin. We purified the bacteriocins using the IMPACT method and determined the respective concentrations using a Bradford standard protein assay with Bovine Serum Albumin (BSA). The first key criteria in order to purify the bacteriocins were to correctly incorporate the bacteriocin into the IMPACT vector pTXB1. We identified successful ligation between our bacteriocins and the pTXB1 with colony PCR, thus the first key criteria were achieved. Check out Demonstrate and Results for specification. Let the purification begin!

Purified bacteriocins inhibit the growth of MRSA and P. aeruginosa. Our MIC test shows growth inhibition of the strains MRSA:USA300 (S.aureus), MRSA:CC398 (S.aureus), hetero-VISA (S.aureus) and Pseudomonas aeruginosa. The bacteriocins LacticinQ and the hybrid Laterosporulin-ThuricinS did not elicit their activity towards P. aeruginosa. However, the absence of inhibition could be due to a higher MIC value, i.e. the need of a higher concentration to inhibit growth than used in the MIC test, which still leaves the hybrid as a potential inhibitor of P. aeruginosa.

Synergistic effect of bacteriocins

Compared to traditional antibiotic the bacteriocins has similar or better effect. The bacteriocins shows inhibition of growth towards MRSA strains and P. aeruginosa at concentrations where the traditional antibiotics does not elicit an effect. The bacteriocins thus show promising results to support the idea of bacteriocins being a supplement for traditional antibiotics of which multiresistant bacterias has become less sensitive towards.

The bacteriocins inhibit growth of the respective strains BUT the bacteriocins also showed synergistic effect. The synergistic effect is shown by a decrease in MIC when the bacteriocin Laterosporulin and ThuricinS are combined as a hybrid compared to their MIC value as single proteins. The hybrid LacticinQ-LacticinZ also shows a decreased MIC compared to LacticinQ as a single acting bacteriocin. The absence of inhibition towards P. aeruginosa by Laterosporulin-ThuricinS when in a hybrid, compared to their single protein effect could be stated as a loss of effect. However the MIC values overall decrease towards the S. aureusstrains indicating a stronger effect. The observation leaves the possibility of a gain of effect towards strains not tested in the MIC test. The gain of effect could possible prove another characteristic of the designed hybrid bacteriocins. This leaves the opportunity to design an antimicrobial compound as needed.

Our bacteriocins face AMR

The bacteriocins could serve as a supplement for traditional antibiotics, which bacterias are less sensitive towards. In the case our purified bacteriocins inhibit the growth of methicillin resistant S. aureus strains. It could be hypothesized that a combination of traditional antibiotics with bacteriocins could elicit a synergistic effect towards resistant bacterial strains. This leave us with the opportunity to shift the balance of resistance and face the evolution of antimicrobial resistance (Dan, Y., M. P. Zacharof and R. W. Lovitt (2012)).