Functional analysis of luxS in the probiotic strain Lactobacillus rhamnosus GG reveals a central metabolic role important for growth and Biofilm formation
Functional analysis of luxS in the probiotic strain Lactobacillus rhamnosus GG reveals a central metabolic role important for growth and Biofilm formation
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DOI：
10.1128/jb.01394-06
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发表时间：
2007-02-01
影响因子：
3.2
通讯作者：
Vanderleyden, Jos
中科院分区：
文献类型：
--
作者：
Lebeer, Sarah;De Keersmaecker, Sigrid C. J.;Vanderleyden, Jos
群体感应通过小分子通讯参与多细胞行为的调控。鉴于胃肠道微生物群的数量和多样性，假设该群落的成员进行交流以协调各种适应过程。AI-2被认为是由LuxS酶合成的通用细菌信号分子，其形成活化甲基循环的组成部分。我们以前曾报道过，有充分证据证明的益生菌菌株鼠李糖乳杆菌GG，一种人类分离株，产生AI-2样分子。在本研究中，我们鉴定了L.鼠李糖luxS似乎位于一个操纵子与yxjH基因编码一个推定的钴胺素独立的蛋氨酸合酶。计算机模拟分析揭示了推定的yxjH-luxS操纵子的前导序列中的甲硫氨酸特异性T盒。然而，转录分析表明，luxS主要表达为单顺反子转录本。构建luxS基因敲除突变体，证实luxS基因在L.鼠李糖然而，这种突变也导致了多效性的影响，这种挑剔的菌株的生长。半胱氨酸、泛酸、叶酸和生物素可以部分补充生长，表明luxS在L.鼠李糖有趣的是，luxS突变体也表现出单种生物膜形成的缺陷。用化学合成的（S）-4，5-二羟基-2，3-戊二酮、与野生型共培养以及营养补充进行的实验表明，这种缺陷的主要原因具有代谢性质。此外，我们的数据表明，抑制突变很可能发生在luxS突变的L。鼠李糖因此，对luxS相关研究的结果应谨慎解读。
Quorum sensing is involved in the regulation of multicellular behavior through communication via small molecules. Given the high number and diversity of the gastrointestinal microbiota, it is postulated that members of this community communicate to coordinate a variety of adaptive processes. AI-2 is suggested to be a universal bacterial signaling molecule synthesized by the LuxS enzyme, which forms an integral part of the activated methyl cycle. We have previously reported that the well-documented probiotic strain Lactobacillus rhamnosus GG, a human isolate, produces AI-2-like molecules. In this study, we identified the luxS homologue of L. rhamnosus GG. luxS seems to be located in an operon with a yxjH gene encoding a putative cobalamin-independent methionine synthase. In silico analysis revealed a methionine-specific T box in the leader sequence of the putative yxjH-luxS operon. However, transcriptional analysis showed that luxS is expressed mainly as a monocistronic transcript. Construction of a luxS knockout mutant confirmed that the luxS gene is responsible for AI-2 production in L. rhamnosus GG. However, this mutation also resulted in pleiotropic effects on the growth of this fastidious strain. Cysteine, pantothenate, folic acid, and biotin could partially complement growth, suggesting a central metabolic role for luxS in L. rhamnosus GG. Interestingly, the luxS mutant also showed a defect in monospecies biofilm formation. Experiments with chemically synthesized (S)-4,5-dihydroxy2,3-pentanedione, coculture with the wild type, and nutritional complementation suggested that the main cause of this defect has a metabolic nature. Moreover, our data indicate that suppressor mutations are likely to occur in luxS mutants of L. rhamnosus GG. Therefore, results of luxS-related studies should be carefully interpreted.