Listeria monocytogenesσ^BModulates PrfA-Mediated Virulence Factor Expression

Abstract

Listeria monocytogenes

Refinement of the Listeria monocytogenes σB regulon through quantitative proteomic analysis

“…opuCC (i) is also preceded by a putative s B -dependent promoter and (ii) belongs to the four-gene opuC operon that has been identified in (Fraser et al, 2003;Sue et al, 2003). lmo0265, which had a significant P c value and a FC of 8.0 reported in the Oliver et al (2010) microarray study, did not show evidence for differential expression in the two other array studies (Ollinger et al, 2009;Raengpradub et al, 2008), which used an EGD-e array that had an lmo0265 probe with low (71 %) homology to the 10403S lmo0265 gene, likely leading to a false-negative result in these two studies.…”

“…A meta-analysis of three published microarray studies was performed to identify genes that showed differential transcript levels between the L. monocytogenes parent strain 10403S and an isogenic DsigB strain. Two of these studies used 10403S and an isogenic DsigB strain (Oliver et al, 2010;Raengpradub et al, 2008), while one study (Ollinger et al, 2009) used an L. monocytogenes 10403S prfA* strain, which constitutively expresses an active form of the virulence gene transcriptional activator PrfA, and an isogenic prfA*DsigB strain. Two of these studies (Ollinger et al, 2009;Raengpradub et al, 2008) used the same set of microarray probes, which were designed based on the genome sequence of strain EGD-e, while the other study (Oliver et al, 2010) used a set of microarray probes designed based on four different genomes.…”

“…The other proteins with lower expression levels were Lmo0427 (fructose-specific PTS system IIB component), Lmo0484 (haem-degrading monooxygenase, IsdG) and Lmo2648 (similar to phosphotriesterase), which showed FC of 21.56, 21.53 and 21.60, respectively. The genes encoding these six proteins also had significant P c values in the microarray meta-analysis and displayed negative FC ranging from 21.6 to 21.1 in three (lmo2648; lmo1998; lmo2002) or two (lmo0484; lmo0427; lmo1997) microarray studies in DsigB stationary phase cells (Oliver et al, 2010;Ollinger et al, 2009;Raengpradub et al, 2008). No genes were identified as negatively regulated by s B in the RNA-Seq study (Oliver et al, 2009).…”

“…A microarray study by Raengpradub et al (2008), comparing transcript levels in L. monocytogenes 10403S and an isogenic DsigB null mutant grown to stationary phase or exposed to salt stress, identified 168 genes as positively regulated by s B [P,0.05; fold change (FC) ¢2.0]. A microarray study by Ollinger et al (2009) characterized transcript levels in stationary phase cells of L. monocytogenes 10403S and DsigB mutant strains with a constitutively active PrfA protein, which forms a regulatory network with s B that contributes to virulence gene expression and host infection by L. monocytogenes. In this study .200 genes were identified as having significant s B effects with FC ¢1.5 between the parent and mutant strain.…”

The arsenal of virulence factors deployed byListeria monocytogenesto promote its cell infection cycle

“…188 It is interesting to note that a significant subset of PrfA-regulated genes have potential σ B promoter sequences. 180 In addition, recent evidence has arisen suggesting that σ B fine-tunes prfA expression inside host cells to avoid overexpression of virulence genes, 189 which could result in excessive host cell damage and thus impair the success of bacteria in establishing infection. This finding highlights the overlap that exists between the control of the general stress response and the control of virulence-related functions.…”