Introduction N -acetylglucosamine (GlcNAc) serves as a signaling molecule that triggers a variety of physiological responses in microorganisms. However, its regulatory roles in metabolite biosynthesis and siderophore production in Lysobacter sp. 3655 remain unclear, especially regarding the quorum sensing (QS) signal 4-hydroxybenzoic acid (4-HBA) and the siderophore lysochelin under iron-deficient conditions. This study aimed to explore the regulatory effects of GlcNAc on metabolite profiles and lysochelin biosynthesis in Lysobacter sp. 3655. Methods Lysobacter sp. 3655 was cultured in oligotrophic medium with GlcNAc induction. The induced differential metabolite was isolated and structurally identified by nuclear magnetic resonance and liquid chromatography-mass spectrometry. Gene deletion mutants of GlcNAc catabolic genes ( nagA , nagE2 ), and L-phenylalanine biosynthesis gene (pheA) were constructed, as well as multiple deletion mutants in the lenB2 (4-HBA biosynthetic gene) mutant background. Growth status and lysochelin yield of these mutants were evaluated under iron-deficient conditions. Exogenous complementation assays were performed using 4-HBA, GlcNAc, p -hydroxybenzaldehyde, cinnamic acid, and p-hydroxycinnamic acid to verify their functional effects. Results GlcNAc specifically induced the production of a unique metabolite in Lysobacter sp. 3655, which was identified as p -hydroxybenzaldehyde. Deletion of nagA , nagE2 , or pheA completely abolished GlcNAc-induced p -hydroxybenzaldehyde biosynthesis. The lenB2 mutant showed significant growth defects and remarkably decreased lysochelin production under iron limitation, while exogenous 4-HBA or GlcNAc restored both phenotypes. Further disruption of nagA , nagE2 , or pheA in the lenB2 mutant eliminated the complementation effect of GlcNAc on lysochelin production. p -hydroxybenzaldehyde restored lysochelin biosynthesis by converting to 4-HBA, and the L-phenylalanine catabolic intermediates cinnamic acid and p-hydroxycinnamic acid also rescued the growth and lysochelin production defects of the lenB2 mutant. Discussion Our results reveal that GlcNAc regulates two metabolic pathways in Lysobacter sp. 3655: it promotes p -hydroxybenzaldehyde production through GlcNAc catabolism and L-phenylalanine metabolism, and restores lysochelin biosynthesis in the QS-deficient lenB2 mutant via either 4-HBA converted from p -hydroxybenzaldehyde or alternative pathways mediated by L-phenylalanine catabolites. These findings uncover a novel regulatory network controlling lysochelin biosynthesis in Lysobacter sp. 3655, providing important references for investigating the biocontrol mechanisms of Lysobacter species.
Lin et al. (Fri,) studied this question.