Role of repressor MogR in flagellar biosynthesis of Listeria monocytogenes at low temperatures

Abstract:

[Objective] Listeria monocytogenes (Lm) is a ubiquitous foodborne pathogen causing listeriosis. Lm can grow at low temperatures and thus may cause safety problems of refrigerated food and threaten the public health. The growth of Lm at low temperatures involves the inhibition of flagellar gene expression, which restricts flagellar biosynthesis. MogR is a transcriptional repressor which represses the expression of flagellar genes during intracellular infection and during extracellular growth of Lm at 37 ℃, resulting in no biosynthesis of flagella. Whereas MogR is deprived of repression function and the bacteria produce flagella during growth at 20–30 ℃. Our studies demonstrated that Lm significantly reduced the flagellar production at 4 ℃, but the molecular mechanism of which remained unclear. This study aims to reveal the relationship between the reduction of flagella and MogR repression at 4 ℃. [Methods] We constructed the mogR-deleted mutant ΔmogR and the flagellin gene flaA-deleted mutant ΔflaA (as the control strain with no flagella), and their complementary strains cΔmogR and cΔflaA with the Lm strain ATCC 19115 as the parental strain. Then, we analyzed the swarming motility, flagellar biosynthesis, and transcriptional levels of flagellar genes in above five strains at 4 ℃, 28 ℃, and 37 ℃, respectively. The growth curves of these strains were determined at 4 ℃, 28 ℃, and 37 ℃, respectively. [Results] Compared with the parental strain, ΔmogR showed significantly increased in motility, flagellar biosynthesis, and transcriptional levels of flagellar genes (P<0.01, 0.001, and 0.001, respectively) at 4 ℃. The growth of ΔmogR markedly decreased compared with the parental strain (P<0.05) at 4 ℃. The data of motility, flagellar biosynthesis, and transcriptional levels of flagellar genes in cΔmogR had no significant differences compared with the parental strain. [Conclusion] The reduction in flagellar biosynthesis was associated with the repression function of MogR in Lm at 4 ℃. The reduction in flagellar biosynthesis was of benefit to Lm proliferation at low temperatures. This study enriched our understanding of the mechanism of Lm growth at low temperatures.