Project description:Antimicrobial resistance is a leading mortality factor worldwide. Here we report the discovery of clovibactin, a new antibiotic, isolated from uncultured soil bacteria. Clovibactin efficiently kills drug-resistant Gram-positivebacterial pathogens without detectable resistance. Using biochemical assays,solid-state NMR, and atomic force microscopy, we dissect its mode of action. Clovibactin blocks cell wall synthesis by targeting pyrophosphate of multiple essential peptidoglycan precursors (C55PP, Lipid II, LipidWTA). Clovibactin uses anunusual hydrophobic interface to tightly wrap aroundpyrophosphate, butbypasses the variable structural elements of precursors, accounting for the lack of resistance. Selective and efficient target binding is achieved by the sequestration of precursors into supramolecular fibrils that only form on bacterial membranes that contain lipid-anchored pyrophosphate groups.Uncultured bacteria offer a rich reservoir of antibiotics with new mechanisms of action that could replenish the antimicrobial discovery pipeline.
Project description:The human liver contains multiple cell types whose epigenetic patterns are undetermined. We examined the promoter methylome of purified and uncultured hepatic stellate cells (HSCs), hepatocytes (HEPs) and liver sinusoidal endothelial cells (LSECs), by methylated DNA immunoprecipitation (MeDIP) and array hybridization. Uncultured HSCs, LSECs and Heps show ~7000-8000 methylated promoters, with 60-70% similarity between all cell types. GO analysis for commonly methylated genes reveals involvement in germ cell development, segregating germ-line from somatic lineage methylation. HSCs, LSECs and HEPs also contain ~500-1000 uniquely methylated promoters; these are implicated in signaling and biosynthetic processes (HSCs), lipid transport and metabolism (LSECs), and chromatin assembly (HEPs). The promoter methylome of culture-activated HSCs deviates from that of their uncultured (quiescent) counterparts. HSC culture-induced activation also enhances methylation differences between individual donors; however this does not necessarily relate to changes in gene expression. HSc activation results in a net gain of promoter DNA methylation, despite the demethylation and de novo methylation of thousands of promoters. Our data provide to our knowledge the first genome-wide maps of promoter DNA methylation in human purified and uncultured liver cell types. Although methylation profiles are largely similar between HSCs, LSECs and hepatocytes, the detection of cell type-specific methylation patterns suggests a differential epigenetic programming of these cell types in the liver.