Figure 1.

Disparity between RNA-Seq data and those obtained at the protein level for the ecgA (STM1940) gene of S. Typhimurium. (A) expression profiles obtained by RNA-Seq for the genomic region in which ecgA is located. These profiles were obtained from intracellular bacteria following infection of macrophages (see Srikumar et al.)¹⁰ and from bacteria grown in media mimicking different infection-relevant conditions (see Kröger et al.)⁸ The image was mounted from the publicly available S. Typhimurium gene expression compendium (http://bioinf.gen.tcd.ie/cgi-bin/salcom.pl?db = salcom_mac_HL); (B) EcgA protein levels detected in bacteria grown in LB medium up to late stationary phase (LSP) or medium exponential phase (MEP); (C) EcgA levels in bacteria grown in ISM minimal medium to LSP and MEP. Protein extracts were prepared from wild-type (WT) and a ΔphoP mutant. Note the absence of reads in the RNA expression profile for ecgA (STM1940) in the LB medium-LSP and in low Mg²⁺ medium, conditions in which the EcgA protein is produced (see also Rico-Pérez et al.).¹² In concordance with transcriptomic data obtained from intracellular S. Typhimurium isolated from fibroblasts³¹ and the RNA-Seq data obtained in bacteria infecting macrophages,¹⁰ EcgA protein levels increase notoriously in intracellular bacteria by a regulation mediated by the PhoP-PhoQ two-component system (see Rico-Pérez et al.)¹².