A hidden layer of the bacterial envelope stress response

Infection diseases caused by viruses and bacteria represent major threats for human health, livestock and agriculture. Gram-negative bacteria of the family Enterobacteriaceae such as pathogenic E. coli, Salmonella and Klebsiella species are of particular concern as resistances against currently used antibiotics are rapidly emerging, demanding for novel therapies. The bacterial cell envelope provides the major line of defense against environmental stresses including many antibiotics. The afore mentioned bacteria are in particular protected by a three- layered envelope structure consisting of a cell wall, which is sandwiched between an inner and an outer membrane. The surface of the outer membrane is covered with lipopolysaccharides (LPS), which provide additional protection against detrimental conditions. Receptor proteins in the envelope monitor the environment and activate intracellular signaling transduction pathways through which the bacteria may adapt to changing conditions. When bacteria are exposed to envelope stress such as antibiotics that target the LPS layer, they activate envelope stress response systems to protect themselves. However, the mechanisms counteracting LPS damage remain largely unclear. In this project, we want to understand how a so far unrecognized envelope stress response system responds to LPS damage and achieves protection and repair.