The BfmRS stress response protects <i>Acinetobacter baumannii</i> against defects in outer membrane lipoprotein biogenesis

As the cell's surface, the outer membrane (OM) of bacteria, such as <i>Acinetobacter baumannii</i>, is continuously under assault from the environment or host. OM integrity is needed for cell survival, and envelope stress responses (ESRs) act to detect and repair any defects. ESRs are well-defined in <i>Escherichia coli</i> but are poorly conserved. We sought to identify an ESR for the essential process of OM lipoprotein biogenesis in <i>A. baumannii</i>. We found that the BfmRS two-component system performs this function and does so without relying on its NlpE sensor homolog, suggesting a novel mechanism of stress sensing is involved in <i>A. baumannii</i>. Our work identifies a key cellular role for BfmRS.