Overuse of broad-spectrum antibiotics leads to an increasing number of bacteria developing resistance, which seriously threatens our ability to treat infections and perform medical procedures that require prophylactic antibiotic treatment. At the same time, broad-spectrum antibiotics disrupt the natural bacterial flora, negatively affecting human health. There is therefore an urgent need for new medicines that selectively target disease-causing bacteria. My research group has recently identified several new antibiotic molecules with selective activity against Chlamydia trachomatis, a common bacterium that causes sexually transmitted infections and eye infections, which in turn can lead to infertility and blindness, respectively. This bacterium has a unique ability to grow and multiply inside human cells, but our molecules were able to eliminate it from infected laboratory cells without harming beneficial bacteria. The aim of the project is to elucidate the mechanisms behind this selectivity. We aim to identify the bacterial - or human - structures that the molecules bind to and block. Furthermore, we will evaluate whether our most potent candidate is effective in a living organism, by investigating whether it can cure the infection in an infection model without affecting the normal microbiota. It is hoped that this work will contribute to the development of more precise and sustainable treatment strategies against infections caused by Chlamydia trachomatis.