Microbial Exopolysaccharide Research Group, Department of Microbiology, Faculty of Pharmacy, Cartuja Campus, University of Granada, 18071 Granada, Spain.
Microbiology (Reading). 2011 Dec;157(Pt 12):3378-3387. doi: 10.1099/mic.0.052167-0. Epub 2011 Oct 20.
Quorum sensing is a cell density-dependent gene expression mechanism found in many Gram-negative bacteria which involves the production of signal molecules such as N-acylhomoserine lactones (AHLs). One significant group of micro-organisms in which quorum sensing has not been previously studied, however, are the moderate halophiles. We describe here the results of our studies of the quorum-sensing system in Halomonas anticariensis FP35(T), which is composed of luxR/luxI homologues: hanR (the putative transcriptional regulator gene) and hanI (the autoinducer synthase gene). To understand how the hanR/hanI system is organized and regulated we conducted RT-PCR and quantitative real-time PCR assays. Transcriptional analysis indicated that the hanR and hanI genes are on the same transcript and that their transcription is growth phase-dependent. HanI seems to be the only autoinducer synthase responsible for the synthesis of AHLs by the bacterium, since the inactivation of hanI resulted in the complete loss of its AHLs. We also found that the hanI gene appears to be transcribed from its own promoter and that its expression does not depend upon HanR. This finding was supported by the fact that the FP35hanR mutant showed AHL-producing activity and hanI expression similar to that of the wild-type strain, the latter being measured by RT-PCR. Moreover, hanR is expressed from its own promoter and appears to be independent of the AHL signalling molecules produced by HanI.
群体感应是一种在许多革兰氏阴性细菌中发现的细胞密度依赖性基因表达机制，涉及信号分子的产生，如 N-酰基高丝氨酸内酯 (AHLs)。然而，在以前的研究中，有一种微生物群体并没有研究过群体感应，那就是中度嗜盐菌。我们在这里描述了我们对 Halomonas anticariensis FP35(T) 群体感应系统的研究结果，该系统由 luxR/luxI 同源物组成：hanR（假定的转录调节基因）和 hanI（自动诱导合成酶基因）。为了了解 hanR/hanI 系统的组织和调节方式，我们进行了 RT-PCR 和定量实时 PCR 检测。转录分析表明，hanR 和 hanI 基因位于同一转录本上，它们的转录依赖于生长阶段。HanI 似乎是唯一负责细菌 AHLs 合成的自动诱导合成酶，因为 hanI 的失活导致其 AHLs 完全丧失。我们还发现，hanI 基因似乎从其自身的启动子转录，其表达不依赖于 HanR。这一发现得到了以下事实的支持：FP35hanR 突变体表现出与野生型菌株相似的 AHL 产生活性和 hanI 表达，后者通过 RT-PCR 进行测量。此外，hanR 从其自身的启动子表达，似乎独立于 HanI 产生的 AHL 信号分子。
