monocytogenes EGD-e rpoN (σL) mutant [22] (Table 2), supporting their negative regulation by σL. Overall, the 56 proteins identified here as negatively regulated by σL represented 13 role categories (e.g., SHP099 chemical structure energy metabolism, transport and binding

proteins, central intermediary metabolism), including 31 proteins Momelotinib in the energy metabolism role category; statistical analyses showed overrepresentation of the role category “energy metabolism” (p < 0.01; Odds Ratio = 5.6) among these 56 proteins. Specific proteins identified as negatively regulated by σL included flagellin (FlaA), chemotaxis protein CheA, and a glutamate-γ-aminobutyric acid (GABA) antiporter (Lmo2362, GadC, GadT2), which have known roles in stress adaptation or virulence in

L. monocytogenes[1, 27]. σC regulates a small number of proteins Previous studies indicated a role for σC in L. monocytogenes thermal adaptive response as well as in cold adaptation [3, 13], however only a few genes have been identified as part of the σC regulon [7]. Similarly, we were only able to identify one protein, Lmo0096, that showed higher protein levels (FC ≥ 1.5; p c < 0.05) in the presence of σC (i.e., the comparison between the ΔBHL and the ΔBCHL strain; Table 3). Lmo0096 has been previously reported to be induced under cold stress in L. monocytogenes[28], supporting a role of σC in response to temperature stress in the bacterium. By comparison, the transcriptomic study by Chaturongakul et al., 2011 only identified lmo0422, which is in the same operon as sigC (lmo0423), as positively regulated by σC[7]. Table 3 Proteins found Fedratinib to be differentially regulated by σ C , as determined by a proteomic comparison between L. monocytogenes 10403S Δ BHL and Δ BCHL Proteina Fold change ΔBHL/ΔBCHL Description Gene name Role categoryb Sub-Role categoryb Proteins GPX6 with positive fold change ( > 1.5) and p < 0.05 (indicating positive regulation by σ C ) Lmo0096c 3.19 mannose-specific PTS system IIAB component ManL mptA Energy metabolism Pyruvate dehydrogenase         Amino acid biosynthesis Aromatic amino acid family         Transport and binding proteins Carbohydrates, organic alcohols,

and acids Proteins with negative fold change ( < -1.5) and p < 0.05 (indicating negative regulation by σ C ) Lmo2094 −1.82 hypothetical protein lmo2094 Energy metabolism Sugars Lmo1902 −1.61 3-methyl-2-oxobutanoate hydroxymethyltransferase panB Biosynthesis of cofactors, prosthetic groups, and carriers Pantothenate and coenzyme A aProtein names are based on the L. monocytogenes EGD-e locus. bRole Categories and Sub-Role categories are based on JCVI classification [26]. cPreceded by a putative σL promoter; tggcacagaacttgca; -12 and -24 regions are underlined. We also identified two proteins, Lmo2094 and Lmo1902, that showed higher protein levels in the absence of σC, suggesting negative regulation of these proteins by σC (Table 3).