Haem-iron plays a key role in the regulation of the Ess/type VII secretion system of Staphylococcus aureus RN6390

Abstract

The Staphylococcus aureus type VII protein secretion system (T7SS) plays important roles in virulence and intra-species competition. Here we show that the T7SS in strain RN6390 is activated by supplementing the growth medium with haemoglobin, and its cofactor haemin (haem B). Transcript analysis and secretion assays suggest that activation by haemin occurs at a transcriptional and a post-translational level. Loss of T7 secretion activity by deletion of essC results in upregulation of genes required for iron acquisition. Taken together these findings suggest that the T7SS plays a role in iron homeostasis in at least some S. aureus strains.

A membrane-depolarizing toxin substrate of theStaphylococcus aureusType VII secretion system mediates intra-species competition

“…The EsxC substrate 17 was also exclusively detected in the supernatant of the wild type strain, but only two EsxC peptides were detected and it did not meet the p < 0.01 cut-off (Table S1). EsxB, another previously identified substrate 2, 22 , and EsaE, which is co-secreted with EsaD 6 were not detected in any of our analysis.…”

Functional analysis of the EsaB component of the Staphylococcus aureus Type VII secretion system

“…To examine this quantitatively, we undertook RNA-Seq analysis on RNA prepared from three biological repeats of the RN6390 and esaB strains grown aerobically in TSB to an OD 600 of 1. Note that these experiments were performed at the same time as the RN6390 versus essC RNA-Seq analysis described in [ 15 ] and used the same RN6390 dataset. Fig.…”

“…Clones were selected in E. coli and verified by DNA sequencing. Plasmid pRAB11-esaB-YFP was generated by cloning the 0.3 kb Hpa I/ Eco RI restriction fragment into pRAB11-YFP [ 15 ]. Clones were selected in E. coli and verified by DNA sequencing.…”

“…For RNA-Seq analysis, three biological repeats of the S. aureus esaB strain was grown aerobically in TSB up to an OD 600 of 1 at which point mRNA was prepared (in three technical replicates). This experiment was carried out alongside the RN6390 and essC strains [ 15 ] and followed identical methodology.…”

“…Polyclonal antisera were used at the following dilutions: α-EsxA 1 : 2500 [ 12 ], α-EsxB 1 : 1000 [ 15 ], α-EsxC 1 : 2000 [ 12 ], α-EsaB 1 : 500, α-TrxA 1 : 20 000 [ 25 ] and α-SrtA (Abcam) 1 : 3000. Anti-GFP antibody was obtained from Roche and used according to manufacturer’s instructions.…”