Supplementary Material for: The Tat Pathway Is Prevalent in <b><i>Listeria monocytogenes</i></b> Lineage II and Is Not Required for Infection and Spread in Host Cells

<i>Listeria monocytogenes</i>, 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 <i>L. monocytogenes</i>, was until now only investigated <i>in silico</i>. In <i>L. monocytogenes</i> strain EGDe two genes constitute this pathway, <i>tatC</i><i>(lmo0361)</i> and <i>tatA</i><i>(lmo0362)</i>. Here we show that <i>tatC</i> and <i>tatA</i> are cotranscribed in a bicistronic- and growth-phase-dependent manner, being downregulated in the stationary phase. An EGDe <i>tatAC</i> mutant strain (EGDe Δ<i>tatAC</i>) was constructed, confirming that the Tat pathway is not essential for <i>L.</i><i>monocytogenes</i> survival or biofilm-forming ability. When compared to the wild-type EGDe, deletion of <i>tatAC</i> did not decrease the virulence potential of EGDe Δ<i>tatAC</i> in HT-29 human epithelial cell line and even increased (p < 0.05) the virulence potential for mice. Moreover, we show that <i>tat</i> genes are prevalent in <i>L. monocytogenes</i> 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 <i>L.</i><i>monocytogenes</i>.