Hood Kara S, Rizvi Samie A, Hoppe-Elsholz Guillermo A, Streling Ana P, Panesso Diana, Pratap Shivendra, Shamoo Yousif, Arias Cesar A, Miller William R
Center for Infectious Diseases, Houston Methodist Research Institute, Houston, Texas, USA.
Graduate School of Medical Sciences, Weill Cornell Medical College, New York, New York, USA.
bioRxiv. 2025 Jun 19:2025.06.19.660511. doi: 10.1101/2025.06.19.660511.
Enterococci are gastrointestinal commensals that must defend their cell envelope against antimicrobial peptides derived from the host and other members of the microbiota. The signaling systems LiaFSR and MadRS are pivotal for survival in the presence of antimicrobial peptides and antimicrobial peptide-like antibiotics such as daptomycin. Both systems possess a signaling histidine kinase (LiaS, MadS) and cognate response regulator (LiaR, MadR) that activate transcription of distinct sets of effector genes. Using isogenic deletion strains, we noted differences in daptomycin minimum inhibitory concentration (MIC) between the laboratory strain OG1RF (1.5 μg/mL), OG1RFΔ (0.38 μg/mL), and OG1RFΔ (4 μg/mL). Transcriptional analysis of the MadR regulon showed a daptomycin-dependent increase in and gene expression in the OG1RFΔ background, suggesting activation of the LiaFSR system may provide a cross-regulatory role. Deletion of the gene in OG117Δ was associated with a significant decrease in daptomycin MIC and loss of expression, one of the most differentially expressed genes on activation of the MadR regulon. Using microscale thermophoresis, LiaS showed a similar binding affinity to both LiaR (K 2.42 μM) and MadR (K 5.02 μM), while MadS showed higher affinity for its cognate regulator MadR (K 8.08 μM) than for LiaR (K 25.7 μM). Taken together, our findings indicate that the MadR regulon can be expressed independent of MadS-induced signaling, likely through cross-talk between LiaS and MadR. Thus, enterococci have evolved an interconnected network of cell envelope signaling that permits bacterial survival in the presence of antibiotics and antimicrobial peptides.
肠球菌是胃肠道共生菌,必须保护其细胞包膜免受源自宿主和微生物群其他成员的抗菌肽的侵害。信号系统LiaFSR和MadRS对于在抗菌肽和类抗菌肽抗生素(如达托霉素)存在的情况下生存至关重要。这两个系统都拥有一个信号组氨酸激酶(LiaS、MadS)和同源反应调节因子(LiaR、MadR),它们激活不同效应基因集的转录。使用同基因缺失菌株,我们注意到实验室菌株OG1RF(1.5μg/mL)、OG1RFΔ(0.38μg/mL)和OG1RFΔ(4μg/mL)之间达托霉素最低抑菌浓度(MIC)存在差异。对MadR调控子的转录分析表明,在OG1RFΔ背景下,达托霉素依赖性地增加了和基因表达,这表明LiaFSR系统的激活可能起到交叉调节作用。在OG117Δ中缺失基因与达托霉素MIC显著降低以及表达丧失有关,表达是MadR调控子激活时差异表达最大的基因之一。使用微量热泳技术,LiaS对LiaR(K 2.42μM)和MadR(K 5.02μM)显示出相似的结合亲和力,而MadS对其同源调节因子MadR(K 8.08μM)的亲和力高于对LiaR(K 25.7μM)的亲和力。综上所述,我们的研究结果表明,MadR调控子可以独立于MadS诱导的信号传导而表达,可能是通过LiaS和MadR之间的相互作用。因此,肠球菌已经进化出一个相互连接的细胞包膜信号网络,使细菌能够在抗生素和抗菌肽存在的情况下生存。