A study found that substances released by the probiotic Lactobacillus gasseri can turn off key genes in Helicobacter pylori, making the bacteria less mobile, less able to survive stomach acid, and more vulnerable to the body’s own antimicrobial peptide LL‑37. This means that adding L. gasseri (as a supplement or fermented food) could help your gut fight H. pylori and boost the natural killing power of LL‑37.

<i>Helicobacter pylori</i> infection triggers inflammation that may lead to gastritis, stomach ulcers and cancer. Probiotic bacteria, such as <i>Lactobacillus</i>, have been of interest as treatment options, however, little is known about the molecular mechanisms of <i>Lactobacillus</i>-mediated inhibition of <i>H. pylori</i> pathogenesis. In this work, we investigated the effect of <i>Lactobacillus</i> culture supernatants, so-called conditioned medium (CM), from two gastric isolates, <i>L. gasseri</i> and <i>L. oris</i>, on the expression of transcriptional regulators in <i>H. pylori</i>. Among the four known two-component systems (TCSs), i.e., ArsRS, FlgRS, CheAY and CrdRS, the flagellar regulator gene <i>flgR</i> and the acid resistance associated <i>arsS</i> gene were down-regulated by <i>L. gasseri</i> CM, whereas expression of the other TCS-genes remained unaffected. <i>L. gasseri</i> CM also reduced the motility of <i>H. pylori</i>, which is in line with reduced <i>flgR</i> expression. Furthermore, among six transcription factors of <i>H. pylori</i> only the ferric uptake regulator gene <i>fur</i> was regulated by <i>L. gasseri</i> CM. Deletion of <i>fur</i> 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 <i>H. pylori</i>.