title: Identification of a small molecule signaling factor that regulates the biosynthesis of the antifungal polycyclic tetramate macrolactam HSAF in Lysobacter enzymogenes.
abstract: Lysobacter species are emerging as new sources of antibiotics. The regulation of these antibiotics is not well understood. Here, we identified a small molecule metabolite (LeDSF3) that regulates the biosynthesis of the antifungal antibiotic heat-stable antifungal factor (HSAF), a polycyclic tetramate macrolactam with a structure and mode of action distinct from the existing antifungal drugs. LeDSF3 was isolated from the culture broth of Lysobacter enzymogenes, and its chemical structure was established by NMR and MS. The purified compound induced green fluorescence in a reporter strain of Xanthomonas campestris, which contained a gfp gene under the control of a diffusible signaling factor (DSF)-inducible promoter. Exogenous addition of LeDSF3 in L. enzymogenes cultures significantly increased the HSAF yield, the transcription of HSAF biosynthetic genes, and the antifungal activity of the organism. The LeDSF3-regulated HSAF production is dependent on the two-component regulatory system RpfC/RpfG. Moreover, LeDSF3 upregulated the expression of the global regulator cAMP receptor-like protein (Clp). The disruption of clp led to no HSAF production. Together, the results show that LeDSF3 is a fatty acid-derived, diffusible signaling factor positively regulating HSAF biosynthesis and that the signaling is mediated by the RfpC/RpfG-Clp pathway. These findings may facilitate the antibiotic production through applied genetics and molecular biotechnology in Lysobacter, a group of ubiquitous yet underexplored microorganisms.
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Han
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Simon
authors.initials: S
authors.lastname: Tombosa
authors.forename: Stephen
authors.initials: S
authors.lastname: Wright
authors.forename: Justin
authors.initials: J
authors.lastname: Huffman
authors.forename: Gary
authors.initials: G
authors.lastname: Yuen
authors.forename: Guoliang
authors.initials: G
authors.lastname: Qian
authors.forename: Fengquan
authors.initials: F
authors.lastname: Liu
authors.forename: Yuemao
authors.initials: Y
authors.lastname: Shen
authors.forename: Liangcheng
authors.initials: L
authors.lastname: Du
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D017930:Genes, Reporter; D053528:Lysobacter / Q000201:enzymology* / Q000235:genetics*; D009682:Magnetic Resonance Spectroscopy; D015398:Signal Transduction; D013696:Temperature
chemical_list: D000935:Antifungal Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial