Temporal Regulation of the Transformasome and Competence Development in .

In the ComX-inducing peptide (XIP) pheromone regulates ComR-dependent transcriptional activation of (or ) the regulator of the late competence regulon. The aims of this study were to identify the ComR-regulated genes and in using 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 in , and . 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 gene were not transformable demonstrating that the DNA uptake pilus is indeed required for competence development in . Competence was a transient state with the regulon shut down after ~15 min even when transcription of had not returned to basal levels, indicating other mechanisms control the exit from competence. The ComX regulon also included genes involved in DNA repair including which we showed to be required for high efficiency transformation. In contrast to and the ComX regulon of did not include which converts the transforming DNA into ssDNA, or , which protects the transforming ssDNA from degradation. EndA appeared to be essential in so 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 between pherotypes or and other species. mutants of , the binding subunit of the general oligopeptide transporter were not transformable, suggesting that it is required for the import of XIP.