Lactobacilli Downregulate Transcription Factors inThat 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 ofpathogenesis. In this work, we investigated the effect ofculture 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 geneand the acid resistance associatedgene were down-regulated byCM, whereas expression of the other TCS-genes remained unaffected.CM also reduced the motility of, which is in line with reducedexpression. Furthermore, among six transcription factors ofonly the ferric uptake regulator genewas regulated byCM. Deletion offurther 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.