Conaway Amy, Mould Dallas L, Todorovic Igor, Hogan Deborah A
Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
J Bacteriol. 2025 May 14:e0018924. doi: 10.1128/jb.00189-24.
The LasR transcription factor plays a role in quorum sensing (QS) across phylogenetically distinct lineages. However, isolates with loss-of-function mutations in (LasR- strains) are commonly found in diverse settings, including infections where they are associated with worse clinical outcomes. In LasR- strains, the LasR-regulated transcription factor RhlR can also be stimulated by the activity of the two-component system PhoR-PhoB in low-inorganic phosphate (Pi) conditions. Here, we demonstrate a novel link between LasR and PhoB in which the absence of LasR increases PhoB activity at physiological Pi concentrations and increases the Pi concentration necessary for PhoB inhibition. PhoB activity was also less sensitive to repression by Pi in mutants lacking different QS regulators (RhlR and PqsR) and in mutants lacking genes required for QS-induced phenazine production, suggesting that decreased phenazine production is one reason for increased PhoB activity in LasR- strains. In addition, the CbrA-CbrB two-component system, which can be more active in LasR- strains, was necessary for increased PhoB activity in LasR- strains, and loss of the CbrA-CbrB-controlled translational repressor Crc was sufficient to activate PhoB in LasR+ . Phenazines and CbrA-CbrB affected PhoB activity independently. The ∆ mutant also had PhoB-dependent growth advantages in the Pi-deplete medium and increased virulence-associated gene expression at physiological Pi, in part through reactivation of QS. This work suggests PhoR-PhoB activity may contribute to the fitness and virulence of LasR- and subsequent clinical outcomes.IMPORTANCELoss-of-function mutations in the gene encoding the quorum sensing (QS) regulator LasR occur frequently and are associated with worse clinical outcomes. We have found that LasR- have elevated PhoB activity at physiological concentrations of inorganic phosphate (Pi). PhoB activity promotes Pi acquisition as well as the expression of QS and virulence-associated genes. Previous work has shown that PhoB induces RhlR, another QS regulator, in a LasR- mutant in low-Pi conditions. Here, we demonstrate a novel relationship wherein LasR represses PhoB activity through the production of phenazines and Crc-mediated translational repression. This work suggests PhoB activity may contribute to the increased virulence of LasR- .
LasR转录因子在系统发育上不同的谱系中参与群体感应（QS）。然而，在多种环境中普遍发现存在功能丧失突变的分离株（LasR-菌株），包括在感染中，它们与更差的临床结果相关。在LasR-菌株中，LasR调控的转录因子RhlR在低无机磷酸盐（Pi）条件下也可被双组分系统PhoR-PhoB的活性刺激。在此，我们证明了LasR与PhoB之间的一种新联系，即LasR的缺失在生理Pi浓度下增加了PhoB的活性，并增加了抑制PhoB所需的Pi浓度。在缺乏不同QS调节因子（RhlR和PqsR）的突变体以及缺乏QS诱导吩嗪产生所需基因的突变体中，PhoB活性对Pi抑制的敏感性也较低，这表明吩嗪产生减少是LasR-菌株中PhoB活性增加的一个原因。此外，在LasR-菌株中可能更活跃的CbrA-CbrB双组分系统，对于LasR-菌株中PhoB活性的增加是必需的，而CbrA-CbrB控制的翻译阻遏物Crc的缺失足以在LasR+菌株中激活PhoB。吩嗪和CbrA-CbrB独立影响PhoB活性。∆突变体在Pi耗尽培养基中也具有PhoB依赖性生长优势，并且在生理Pi条件下增加了毒力相关基因的表达，部分是通过QS的重新激活。这项工作表明PhoR-PhoB活性可能有助于LasR-菌株的适应性和毒力以及随后的临床结果。
重要性
编码群体感应（QS）调节因子LasR的基因中的功能丧失突变频繁发生，并且与更差的临床结果相关。我们发现LasR-菌株在无机磷酸盐（Pi）的生理浓度下具有升高的PhoB活性。PhoB活性促进Pi摄取以及QS和毒力相关基因的表达。先前的研究表明，在低Pi条件下，PhoB在LasR-突变体中诱导另一种QS调节因子RhlR。在此，我们证明了一种新的关系，其中LasR通过吩嗪的产生和Crc介导的翻译抑制来抑制PhoB活性。这项工作表明PhoB活性可能有助于LasR-菌株毒力的增加。
