Role of flhA and motA in growth of Listeria monocytogenes at low temperatures

Abstract While temperature-dependent induction of flagella is a well-characterized phenomenon in Listeria monocytogenes , the essentiality of increased flagellum production during growth at low temperatures remains unclear. To study this relationship, we compared the relative expression levels of two motility genes, flhA and motA , at 3 °C, 25 °C and 37 °C in L. monocytogenes strain EGD-e by using qRT-PCR, and compared the growth curves, motility, and flagellation between the wild-type and flhA and motA deletion mutants. The relative expression levels of flhA and motA at 3 °C were significantly higher than at 37 °C (p  flhA transcripts was also significantly higher than at 25 °C (p  ΔflhA and ΔmotA strains at 600 nm were significantly lower than those of the wild-type (p  ΔflhA and ΔmotA were nonmotile at all three temperatures. At 25 °C, the number of flagellated cells of ΔmotA was notably reduced compared with the wild-type, whereas ΔflhA appeared nonflagellated at all temperatures. The results suggest that flhA and motA play a role in the cold tolerance of L. monocytogenes strain EGD-e, and that motile flagella may be needed for optimal cold stress response of L. monocytogenes .