Differential Regulation of Listeria monocytogenes Internalin and Internalin-Like Genes by σ B and PrfA as Revealed by Subgenomic Microarray Analyses

The Listeria monocytogenes genome contains more than 20 genes that encode cell surface–associated internalins. To determine the contributions of the alternative sigma factor σ^B and the virulence gene regulator PrfA to internalin gene expression, a subgenomic microarray was designed to contain two probes for each of 24 internalin-like genes identified in the L. monocytogenes 10403S genome. Competitive microarray hybridization was performed on RNA extracted from (i) the 10403S parent strain and an isogenic ΔsigB strain; (ii) 10403S and an isogenic ΔprfA strain; (iii) a (G155S) 10403S derivative that expresses the constitutively active PrfA (PrfA*) and the ΔprfA strain; and (iv) 10403S and an isogenic ΔsigBΔprfA strain. σ^B- and PrfA-dependent transcription of selected genes was further confirmed by quantitative reverse-transcriptase polymerase chain reaction. For the 24 internalin-like genes examined, (i) both σ^B and PrfA contributed to transcription of inlA and inlB, (ii) only σ^B contributed to transcription of inlC2, inlD, lmo0331, and lmo0610; (iii) only PrfA contributed to transcription of inlC and lmo2445; and (iv) neither σ^B nor PrfA contributed to transcription of the remaining 16 internalin-like genes under the conditions tested.