ROS-induced allosteric modulation of NikR promotes Helicobacter pylori biofilm formation by attenuating FlgR-dependent inhibition of the molybdate transport system.

Helicobacter pylori biofilm formation is crucial for its persistence and transmission, constituting a notable public health concern. Understanding the regulatory mechanisms driving biofilm initiation is vital for developing effective control strategies. This study reveals a previously uncharacterized regulatory mechanism where reactive oxygen species (ROS) promote H. pylori biofilm formation by modulating the key flagellar regulator FlgR and the molybdate transport system ModABD. We demonstrate that FlgR acts as a repressor of biofilm development. Mechanistically, FlgR inhibits the transcription of the modABD operon, essential for biofilm formation, by suppressing the activity of sigma factor σ28. Crucially, we identify the nickel-responsive regulator NikR as a repressor of flgR expression. ROS induces a conformational change in NikR, converting it to its DNA-binding holo-form, which directly binds the flgR promoter and represses its expression. This repression alleviates FlgR-mediated inhibition of σ28, thereby de-repressing the modABD operon and facilitating the transition from planktonic to biofilm growth. Our findings uncover a previously unknown ROS-NikR-FlgR-σ28-ModABD signaling axis governing H. pylori biofilm formation.