title: 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<0.01). At 3°C, the level of flhA transcripts was also significantly higher than at 25°C (p<0.01). Growth curve analysis showed that at 3°C both the growth rates and maximum optical densities of ΔflhA and ΔmotA strains at 600 nm were significantly lower than those of the wild-type (p<0.001), while no significant differences were observed between the wild-type and the mutants at 37°C, and 25°C. Mutant strains 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.
authors.affiliation: Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland. mirjami.s.mattila@helsinki.fi
authors.forename: Mirjami
authors.initials: M
authors.lastname: Mattila
authors.forename: Miia
authors.initials: M
authors.lastname: Lindström
authors.forename: Panu
authors.initials: P
authors.lastname: Somervuo
authors.forename: Annukka
authors.initials: A
authors.lastname: Markkula
authors.forename: Hannu
authors.initials: H
authors.lastname: Korkeala
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003080:Cold Temperature; D058639:Cold-Shock Response; D005407:Flagella / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D008089:Listeria monocytogenes / Q000235:genetics / Q000254:growth & development*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D001426:Bacterial Proteins; C080688:FlhA protein, Bacteria; D008565:Membrane Proteins; C063010:MotA protein, Bacteria