Lactobacilli Downregulate Transcription Factors in Helicobacter pylori That Affect Motility, Acid Tolerance and Antimicrobial Peptide Survival

infection triggers inflammation that may lead to gastritis, stomach ulcers and cancer. Probiotic bacteria, such as , have been of interest as treatment options, however, little is known about the molecular mechanisms of -mediated inhibition of pathogenesis. In this work, we investigated the effect of culture supernatants, so-called conditioned medium (CM), from two gastric isolates, and , on the expression of transcriptional regulators in . Among the four known two-component systems (TCSs), i.e., ArsRS, FlgRS, CheAY and CrdRS, the flagellar regulator gene and the acid resistance associated gene were down-regulated by CM, whereas expression of the other TCS-genes remained unaffected. CM also reduced the motility of , which is in line with reduced expression. Furthermore, among six transcription factors of only the ferric uptake regulator gene was regulated by CM. Deletion of further led to dramatically increased sensitivity to the antimicrobial peptide LL-37. Taken together, the results highlight that released/secreted factors of some lactobacilli, but not all, downregulate transcriptional regulators involved in motility, acid tolerance and LL-37 sensitivity of .