The bacterium Pseudomonas aeruginosa negatively regulates denitrification under anerobic conditions by two acyl-homoserine lactone quorum-sensing (QS) systems called las and rhl . However, it is unknown whether these systems have the same effect on denitrification in aerobic conditions. In this study, we investigated the regulation of las and rhl systems on aerobic denitrification. We showed that the removal of nitrate in P. aeruginosa PAO1 was repressed by both the las and rhl systems. The las and rhl systems had negative effects on activities of denitrifying enzymes NAP, NIR, NOR, and NOS. At the level of transcription, both QS systems inhibited the expression of target genes napA , nirS , norB , norC , and nosZ . Furthermore, the addition of an acylase, which degrades the acyl-homoserine lactone signals (AHLs), to wild type resulted in an increase in the removal of nitrate. Additionally, in aerobic denitrification process, the transcription factor DNR, which controls denitrification, was repressed by both QS systems. The results implied that modulation of QS in denitrifying bacteria, possibly through quorum quenching or QS inhibition, could help to improve the reduction of nitrate in wastewater treatment.

中文翻译：

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las和rhl群体感应对铜绿假单胞菌PAO1好氧反硝化作用的调控

铜绿假单胞菌在厌氧条件下通过两个称为 las 和 rhl 的酰基高丝氨酸内酯群体感应 (QS) 系统负向调节反硝化作用。然而，尚不清楚这些系统是否对好氧条件下的反硝化具有相同的影响。在这项研究中，我们研究了 las 和 rhl 系统对好氧反硝化的调节。我们发现 las 和 rhl 系统都抑制了铜绿假单胞菌 PAO1 中硝酸盐的去除。las 和rhl 系统对反硝化酶NAP、NIR、NOR 和NOS 的活性有负面影响。在转录水平上，两个 QS 系统都抑制了目标基因 napA、nirS、norB、norC 和 nosZ 的表达。此外，添加酰基高丝氨酸内酯信号 (AHL) 的酰基转移酶，野生型导致硝酸盐去除增加。此外，在好氧反硝化过程中，控制反硝化作用的转录因子 DNR 被两个 QS 系统抑制。结果表明，在反硝化细菌中调节 QS，可能通过群体淬灭或 QS 抑制，有助于改善废水处理中硝酸盐的还原。