title: Temporal Regulation of the Transformasome and Competence Development inStreptococcus suis.
abstract: InS. suisthe ComX-inducing peptide (XIP) pheromone regulates ComR-dependent transcriptional activation ofcomX(orsigX) the regulator of the late competence regulon. The aims of this study were to identify the ComR-regulated genes and inS. suisusing genome-wide transcriptomics and identify their function based on orthology and the construction of specific knockout mutants. The ComX regulon we identified, includes all homologs of the "transformasome" a type 4-like pilus DNA binding and transport apparatus identified inStreptococcus pneumoniae, Streptococcus mutans, andStreptococcus thermophilus. A conserved CIN-box (YTACGAAYW), predicted to be bound by ComX, was found in the promoters of operons encoding genes involved in expression of the transformasome. Mutants lacking the major pilin genecomYCwere not transformable demonstrating that the DNA uptake pilus is indeed required for competence development inS. suis. Competence was a transient state with thecomXregulon shut down after ~15 min even when transcription ofcomXhad not returned to basal levels, indicating other mechanisms control the exit from competence. The ComX regulon also included genes involved in DNA repair includingcinAwhich we showed to be required for high efficiency transformation. In contrast toS. pneumoniaeandS. mutansthe ComX regulon ofS. suisdid not includeendAwhich converts the transforming DNA into ssDNA, orssbA, which protects the transforming ssDNA from degradation. EndA appeared to be essential inS. suisso we could not generate mutants and confirm its role in DNA transformation. Finally, we identified a putative homolog of fratricin, and a putative bacteriocin gene cluster, that were also part of the CIN-box regulon and thus may play a role in DNA release from non-competent cells, enabling gene transfer betweenS. suispherotypes orS. suisand other species.S. suismutants ofoppA, the binding subunit of the general oligopeptide transporter were not transformable, suggesting that it is required for the import of XIP.
authors.affiliation: Host-Microbe Interactomics, Animal Sciences, Wageningen University Wageningen, Netherlands.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Zaccaria
authors.affiliation: NIZO Food Research B. V. Ede, Netherlands.
authors.forename: Michiel
authors.initials: M
authors.lastname: Wels
authors.affiliation: Host-Microbe Interactomics, Animal Sciences, Wageningen University Wageningen, Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: van Baarlen
authors.affiliation: Host-Microbe Interactomics, Animal Sciences, Wageningen University Wageningen, Netherlands.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Wells
keywords: DNA transformation; Streptococcus suis; bacteriocins; competence; fratricin; pillus; sigma factor X