A two-component system signaling hub controls enterococcal membrane remodeling in response to daptomycin

Daptomycin resistance in Enterococcus faecalis is due to consecutive acquisition of two types of mutation: a primary mutation that constitutively activates the LiaFSR two component system followed by secondary mutations in phospholipid biosynthetic genes. Here, we study how E. faecalis remodels its membrane composition in response to the antibiotic as part of a cell envelope stress response. We show that cell membrane remodelling is due to LTA synthesis by LtaS1. LTA production is under the control of the two component systems LiaFSR, SapRS, and BsrRS and contributes to baseline daptomycin resistance. We propose an updated model of how E. faecalis responds to daptomycin and provide a framework to understand the sequential acquisition of mutations that lead to clinical high-resistance daptomycin resistance. Overall design: We wanted to understand a) if membrane remodelling in wild-type E. faecalis is regulated on the transcriptional level, and b) uncover the LiaFSR regulon during daptomycin stress. Thus, we determined transcriptional changes in wild-type, ?liaR, and ?liaFSR strains exposed to daptomycin. We included three biological replicates of each strain and treated with a subinhibitory concentration of daptomycin for 15 min prior to RNA-Seq analysis. Untreated cultures were used as controls.