The methylome is acid-responsive due to regulation by the two-component system ArsRS and the type I DNA methyltransferase HsdM1 (HP0463).

In addition to its role in genome protection, DNA methylation can regulate gene expression. In this study, we characterized the impact of acidity, phase variation, and the ArsRS TCS on the expression of the Type I m6A DNA methyltransferase HsdM1 (HP0463) of 26695 and their subsequent effects on the methylome. Transcription of 1 increases at least fourfold in the absence of the sensory histidine kinase ArsS, the major acid-sensing protein of 1 exists in the phase-variable operon 1-1.