The YtrBCDEF ABC transporter is involved in the control of social activities inBacillus subtilis

Abstract

Bacillus subtilis develops genetic competence for the uptake of foreign DNA when cells enter the stationary phase and a high cell density is reached. These signals are integrated by the competence transcription factor ComK which is subject to transcriptional, post-transcriptional and post-translational regulation. Many proteins are involved in the development of competence, both to control ComK activity and to mediate DNA uptake. However, the precise function they play in competence development is often unknown. In this study, we have tested whether proteins required for genetic transformation play a role in the activation of ComK or rather downstream of competence gene expression. While these possibilities could be distinguished for most of the tested factors, two proteins (PNPase and the transcription factor YtrA) are required both for full ComK activity and for the downstream processes of DNA uptake and integration. Further analyses of the role of the transcription factor YtrA for the competence development revealed that the constitutive expression of the YtrBCDEF ABC transporter in the ytrA mutant causes the loss of genetic competence. Moreover, constitutive expression of this ABC transporter also interferes with biofilm formation. Since the ytrGABCDEF operon is induced by cell wall-targeting antibiotics, we tested the cell wall properties upon overexpression of the ABC transporter and observed an increased thickness of the cell wall. The composition and properties of the cell wall are important for competence development and biofilm formation, suggesting that the increased cell wall thickness as a result of YtrBCDEF overexpression causes the observed phenotypes.

Not Just Transporters: Alternative Functions of ABC Transporters in Bacillus subtilis and Listeria monocytogenes

“…Recent studies suggest that ABC transporters can also have a direct or indirect effect on PG biosynthesis and remodeling. For instance, it has been shown that the overexpression of the YtrBCDEF ABC transporter of B. subtilis leads to the production of a thicker PG layer [ 65 ]. The transporter YtrBCDEF is encoded in the ytrGABCDEF operon and the GntR family repressor YtrA controls its expression [ 66 , 67 ].…”

“…Interestingly, the expression of the ytrGABCDEF operon was not induced in presence of acetoin [ 66 ], suggesting that the YtrBCDEF transporter might only have an indirect effect on acetoin utilization. The absence of the transcriptional regulator YtrA further led to a complete loss of genetic competence [ 65 , 78 ]. The loss of competence of the ytrA mutant could potentially be explained by an inability of the DNA to reach the competence pilus ComG due to the thicker PG layer produced by this strain [ 65 ]; however, further experiments are required to investigate this.…”

“…The absence of the transcriptional regulator YtrA further led to a complete loss of genetic competence [ 65 , 78 ]. The loss of competence of the ytrA mutant could potentially be explained by an inability of the DNA to reach the competence pilus ComG due to the thicker PG layer produced by this strain [ 65 ]; however, further experiments are required to investigate this. In addition, it remains to be elucidated how the function of the ABC transporter YtrBCDEF is linked to PG biosynthesis and acetoin utilization in B. subtilis .…”