Antibiotic resistance is a major threat to humanity. Many of us have been taking antibiotics for granted. The emergence of drug-resistant ‘superbugs’ has brought back an ‘old’ class of antibiotic, the polymyxins. Unfortunately, this last-line of defence is breached. In the late 2015, the discovery of a new ‘jumping’ polymyxin resistance gene, called mcr, elevates the global urgency due to its ability to spread easily. This PhD project investigates the role of the mcr gene in bacteria, which can be employed to develop strategic plans to eradicate polymyxin resistance and prolong the lifespan of this last-line antibiotic.