DNA methyltransferase HP1208 antagonizes Fur-mediated repression of GlmU to modulate β-lactam susceptibility in Helicobacter pylori

ABSTRACT DNA methyltransferases in Helicobacter pylori regulate processes beyond genome defense, but whether they directly modulate β-lactam susceptibility has remained unclear. Here, we identify the conserved CATG methyltransferase M.HpyAI (HP1208) as a key determinant of cell wall homeostasis and antibiotic response. Deletion of hp1208 in strain 26695 caused a marked increase in β-lactam susceptibility and impaired growth under osmotic stress, consistent with defective peptidoglycan biogenesis. Transcriptomic profiling revealed coordinated repression of cell wall biosynthetic genes, with glmU emerging as the dominant functional target. Ectopic glmU expression restored peptidoglycan content and β-lactam MICs to wild-type values, establishing GlmU as the principal downstream effector of HP1208. Mechanistically, HP1208 methylates a CATG motif in the glmU promoter that resides within a Fur-responsive regulatory segment adjacent to the −10 element. This methyl mark reduces Fur occupancy at the glmU promoter, thereby relieving Fur-mediated repression and sustaining basal glmU transcription. When methylation is lost, Fur occupancy increases, glmU expression declines, and cell wall integrity is impaired. Thus, HP1208 modulates β-lactam susceptibility not simply by broadly remodeling the methylome, but by antagonizing a metal-responsive repressor at a critical peptidoglycan node. We further show that β-lactam exposure lowers intracellular iron availability, promotes the conversion of holo-Fur to apo-Fur, and partially derepresses glmU under methylation-deficient conditions. These findings uncover a coupled epigenetic-iron homeostasis circuit in which HP1208 and Fur coordinate cell-wall precursor production, intrinsic β-lactam susceptibility, and adaptive recovery from antibiotic stress.