Prunty Michael P, Noone David, Devine Kevin M
Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland.
Mol Microbiol. 2018 Apr 12. doi: 10.1111/mmi.13965.
The PhoPR-mediated response to phosphate limitation (PHO response) in Bacillus subtilis subsp subtilis is amplified and maintained by reducing the level of Lipid V composed of poly(glycerol phosphate), a wall teichoic acid (WTA) biosynthetic intermediate that inhibits PhoR autokinase activity. However, the reduction in Lipid V level is effected by activated PhoP∼P, raising the question of how the PHO response is first initiated. Furthermore, that WTA is composed of poly(ribitol phosphate) in Bacillus subtilis subsp spizizenii prompted an investigation of how the PHO response is regulated in that bacterium. We report that the PHO responses of B. subtilis subsp subtilis and subsp spizizenii are distinct. The PhoR kinases of the two B. subtilis subspecies are functionally equivalent and are activated either by the TagA/TarA or TagB/TarB enzyme product. However, they are inhibited by Lipid V composed of poly(glycerol phosphate) but not by Lipid V composed of poly(ribitol phosphate). Therefore, the distinctive PHO responses of these B. subtilis subspecies stem from the differential sensitivity of PhoR kinases to the polyol composition of Lipid V and from the genomic organization of WTA biosynthetic genes and the regulation of their expression.
枯草芽孢杆菌亚种枯草芽孢杆菌中由PhoPR介导的对磷酸盐限制的应答（PHO应答），通过降低由聚（甘油磷酸）组成的脂质V的水平得以增强和维持，脂质V是一种壁磷壁酸（WTA）生物合成中间体，可抑制PhoR自激酶活性。然而，脂质V水平的降低是由活化的PhoP∼P引起的，这就提出了PHO应答如何首先启动的问题。此外，枯草芽孢杆菌亚种斯皮兹森尼氏菌中的WTA由聚（核糖醇磷酸）组成，这促使人们研究该细菌中PHO应答是如何调控的。我们报道，枯草芽孢杆菌亚种枯草芽孢杆菌和亚种斯皮兹森尼氏菌的PHO应答是不同的。这两个枯草芽孢杆菌亚种的PhoR激酶在功能上是等效的，并且可被TagA/TarA或TagB/TarB酶产物激活。然而，它们被由聚（甘油磷酸）组成的脂质V抑制，而不被由聚（核糖醇磷酸）组成的脂质V抑制。因此，这些枯草芽孢杆菌亚种独特的PHO应答源于PhoR激酶对脂质V多元醇组成的不同敏感性，以及WTA生物合成基因的基因组组织及其表达调控。
