MD simulations have played a crucial role in advancing our understanding of how polymyxins interact with LPS. A study by demonstrated that the rigidity of the cyclic polymyxin scaffold is key for its activity by inducing deformations in the Lipid A portion of the LPS. Additionally, the introduction of phosphate-attached ethanolamine (pEtN) groups contributes to polymyxin resistance by establishing strong salt bridges and hydrogen bonds with the phosphate of the adjacent Lipid A molecule and by further increasing the affinity of Lipid A for Ca 2+ ions by providing two closely tethered phosphate groups . These two phenomena result in the dehydration of the phosphate groups [112], rendering them 2.2 Inhibition of cell wall synthesis: (Not) another brick in the wall less accessible to the positively charged groups of the polymyxins. The energetic penalty of breaking this intricate web of salt bridges and hydrogen bonds underpins the mechanism of mcr-1-mediated colistin resistance observed in Gram-negative species of the ESKAPEE group .