Part:BBa_K2273000
PsrfA: a ComA-dependent promoter of Bacillus subtilis
Usage and Biology
Figure 1: The regulatory system for competence development in Bacillus subtilis. The development of genetic competence is stimulated by quorum sensing due to the secretion of the ComX pheromone and its accumulation in the surrounding medium. (Modified from: Jung et al.) This promoter is part of the well-studied regulatory system for competence development in Bacillus subtilis (Figure 1).
B. subtilis constantly secretes the ComX pheromone (BBa_K2273003), a 9- to 10-amino acid oligopeptide, as a signalling molecule (a). By rising cell-density, the ComX-concentration in the surrounding medium increases until it reaches a threshold and activates ComP, a membrane-spanning protein kinase (b). This mechanism is called quorum sensing.
The kinase reacts to the accumulation of ComX by phosphorylating the response regulator ComA (c) which then works as a transcription factor by binding to several promoters and enhancing their activity (d).
The most important promoter regulated by ComA and involved in competence development is the promoter of the srfA operon (PsrfA). This operon contains not only genes for the production of the antibiotic surfactin (e) but also for ComS (f), another small peptide that prevents the degradation of the autoregulated transcription factor ComK (g). Figure 2: Growth (A) and promoter activity of PsrfA (B) in different media. Wild type (WT, pink) and comX-knockout strains (ΔcomX, dark blue) contain a PsrfA-luxABCDE fusion.
Since the promoter is not only dependent on quorum sensing but also on nutritional conditions, we evaluated the influence of different media (Figure 2). We tested full medium (LB) as well as minimal media (MNGE, MCSE).
Furthermore, we studied the influence of ComX-overproduction on the promoter activity by integrating an inducible copy of comX.
Growth (A) and promoter activity of PsrfA (B) in dependence of xylose-induction. Wild type (WT, pink and light blue) and comX-knockout strain (ΔcomX, black and dark blue) contain a PsrfA-luxABCDE fusion. After 1 hour of incubation (dashed line) the cultures were induced with 1% xylose (light blue and black) or with distilled water (dH2O, pink and dark blue).
The promoter was created and used by TU_Dresden 2017. All assays have been conducted with B. subtilis W168 carrying the promoter fused to the lux operon. Other promoters that haven been evaluated regarding their ComX-dependent activity:
| PsrfA | BBa_K2273000 |
| PrapA | BBa_K2273001 |
| PrapF | BBa_K2273002 |
| PcomG | BBa_K2273012 |
| PcomK mut | BBa_K2273013 |
| None |