Pseudomonas aeruginosa infections represent an important health problem that has been recognized by the World Health Organization as a research priority. A complex regulatory network called the quorum sensing (QS) regulates several P. aeruginosa virulence-related traits, including production of elastase, rhamnolipids and pyocyanin. The avirulent P. aeruginosa strain ATCC 9027 belongs to clade 3, which is the more distant phylogroup in relationship to the other four clades of this species. This strain does not produce QS-regulated virulence factors such as elastase and rhamnolipids when cultured in rich LB medium. We report here that ATCC 9027 harbors a defective LasR protein, presumably due to the presence of an aspartic acid in position 196 instead of a glutamic acid which is the amino acid present in this position in functional LasR proteins of the type strains PAO1 (clade 1) and PA7 (also belonging to clade 3), among others. In addition, we report that ATCC 9027 and PA7 strains present differences compared to the PAO1 strain in lasB which encodes elastase, and in the rhlR regulatory sequences that modify las-boxes, and that these mutations have a little effect in the expression of these genes by a functional LasR transcriptional regulator.

中文翻译：

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离群的铜绿假单胞菌菌株ATCC 9027包含有缺陷的LasR群体感应转录调控因子。

铜绿假单胞菌感染是重要的健康问题，已被世界卫生组织确认为研究重点。一个称为群体感应（QS）的复杂调控网络可调控多种铜绿假单胞菌的毒力相关性状，包括弹性蛋白酶，鼠李糖脂和绿脓素的产生。无毒铜绿假单胞菌菌株ATCC 9027属于进化枝3，与该物种的其他四个进化枝相比，它是较远的系统群。在丰富的LB培养基中培养时，此菌株不会产生QS调节的毒力因子，例如弹性蛋白酶和鼠李糖脂。我们在这里报告ATCC 9027包含有缺陷的LasR蛋白，大概是由于在位置196中存在天冬氨酸，而不是在菌株PAO1类型的功能性LasR蛋白中该位置中存在的氨基酸谷氨酸）和PA7（也属于进化枝3）。此外，我们报告相比，在PAO1菌株ATCC 9027和PA7菌株本差异lasB编码弹性蛋白酶，而在rhlR调节序列，其修改LAS-框，并且这些突变通过功能性LasR转录调节子对这些基因的表达几乎没有影响。