title: The Tat pathway is prevalent in Listeria monocytogenes lineage II and is not required for infection and spread in host cells.
abstract: Listeria monocytogenes, a foodborne pathogenic bacterium, remains a serious public health concern due to its frequent occurrence in food products coupled with a high mortality rate. Bacterial pathogenicity depends greatly on the ability to secrete virulence factors to or beyond the bacterial cell surface. The Tat pathway, one of the secretion systems present in L. monocytogenes, was until now only investigated in silico. In L. monocytogenes strain EGDe two genes constitute this pathway, tatC(lmo0361) and tatA(lmo0362). Here we show that tatC and tatA are cotranscribed in a bicistronic- and growth-phase-dependent manner, being downregulated in the stationary phase. An EGDe tatAC mutant strain (EGDe ΔtatAC) was constructed, confirming that the Tat pathway is not essential for L.monocytogenes survival or biofilm-forming ability. When compared to the wild-type EGDe, deletion of tatAC did not decrease the virulence potential of EGDe ΔtatAC in HT-29 human epithelial cell line and even increased (p < 0.05) the virulence potential for mice. Moreover, we show that tat genes are prevalent in L. monocytogenes strains belonging to genetic lineage II and are generally absent from lineage I, which is more associated with human cases, thus excluding the possibility of using the Tat system as a target for novel antimicrobial compounds targeting L.monocytogenes.
authors.affiliation: CBAA/DRAT, Laboratório de Microbiologia, Instituto Superior de Agronomia, Technical University of Lisbon, Lisbon, Portugal.
authors.forename: Henrique
authors.initials: H
authors.lastname: Machado
authors.forename: António
authors.initials: A
authors.lastname: Lourenço
authors.forename: Filipe
authors.initials: F
authors.lastname: Carvalho
authors.forename: Didier
authors.initials: D
authors.lastname: Cabanes
authors.forename: Birgitte H
authors.initials: BH
authors.lastname: Kallipolitis
authors.forename: Luísa
authors.initials: L
authors.lastname: Brito
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D008089:Listeria monocytogenes / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D008088:Listeriosis / Q000821:virology; D014774:Virulence / Q000235:genetics / Q000502:physiology; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors