Two-component systems (TCS) are one of the signal transduction mechanisms, which sense physiological/biological restraints and respond to changing environmental conditions by regulating the gene expression. Previously, by employing a forward genetic screen (INSeq), we identified that cbrA gene is essential for the fitness of Pseudomonas aeruginosa PGPR2 during root colonization. Here, we report the functional characterization of cbrAB TCS in PGPR2 during root colonization. We constructed insertion mutants in cbrA and its cognate response regulator cbrB. Genetic characterization revealed drastic down-regultion of sRNA crcZ gene in both mutant strains which play a critical role in carbon catabolite repression (CCR). The mutant strains displayed 10-fold decreased root colonization efficiency when compared to the wild-type strain. On the other hand, mutant strains formed higher biofilm on the abiotic surface, and the expression of pelB and pslA genes involved in biofilm matrix formation was up-regulated. In contrast, the expression of algD, responsible for alginate production, and its associated sigma factor algU was significantly down-regulated in mutant strains. We further analyzed the transcript levels of rsmA, controlled by the algU sigma factor, and found that the expression of rsmA was hampered in both mutants. The ability of mutant strains to swim and swarm was significantly hindered. Also, the expression of genes associated with type III secretion system (T3SS) was dysregulated in mutant strains. Taken together, regulation of gene expression by CbrAB TCS is intricate, and we confirm its role beyond carbon and nitrogen assimilation.

双组分系统 (TCS) 是信号转导机制之一，它感知生理/生物约束并通过调节基因表达来响应不断变化的环境条件。以前，通过采用正向遗传筛选 (INSeq)，我们确定cbrA基因对于根定植期间铜绿假单胞菌PGPR2的适应性至关重要。在这里，我们报告了根定植期间PGPR2 中 cbrAB TCS的功能表征。我们在cbrA及其同源反应调节器cbrB 中构建了插入突变体。遗传特征显示 sRNA crcZ的显着下调两种突变菌株中的基因，它们在碳分解代谢物抑制 (CCR) 中起关键作用。与野生型菌株相比，突变菌株的根部定植效率降低了 10 倍。另一方面，突变菌株在非生物表面形成更高的生物膜，并且参与生物膜基质形成的pelB和pslA基因的表达上调。相比之下，负责藻酸盐生产的algD及其相关的西格玛因子algU的表达在突变菌株中显着下调。我们进一步分析的转录水平RSMA，由控制algU σ因子，发现的表达rsmA在两个突变体中都受到阻碍。突变株游动和成群的能力受到显着阻碍。此外，与 III 型分泌系统 (T3SS) 相关的基因表达在突变株中失调。综上所述，CbrAB TCS 对基因表达的调控是复杂的，我们证实了它在碳和氮同化之外的作用。