Functional analysis of luxS in Staphylococcus aureus reveals a role in metabolism but not quorum sensing
Functional analysis of luxS in Staphylococcus aureus reveals a role in metabolism but not quorum sensing
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DOI：
10.1128/jb.188.8.2885-2897.2006
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发表时间：
2006-04-01
影响因子：
3.2
通讯作者：
Winzer, K
中科院分区：
文献类型：
--
作者：
Doherty, N;Holden, MTG;Winzer, K
AI-2在许多细菌中的功能以及产生AI-2的酶LuxS的生理作用仍存在争议。本研究表明，在金黄色葡萄球菌中，luxS基因在sigma（70）依赖性启动子的控制下形成单顺反子转录单元。该基因在多种条件下的生长过程中转录，包括在MAC-T细胞的细胞内生长。AI-2在好氧和厌氧条件下的富培养基中产生，在过渡到固定阶段时达到峰值，但在限定硫的培养基中几乎检测不到。在葡萄糖存在或厌氧条件下，培养物在进入固定相后仍保持相当大的AI-2活性。在各种金黄色葡萄球菌菌株中，luxS的失活并不影响毒力相关的性状，如溶血素和细胞外蛋白酶的产生、生物膜的形成和agr信号系统。相反，在agr突变体中，AI-2的产生保持不变。然而，在限硫培养基中生长的luxS突变体表现出生长缺陷。当与野生型在混合培养中一起生长时，各种金黄色葡萄球菌菌株的luxS突变体在这些条件下竞争生长的能力降低。相比之下，一个互补的luxS突变体和亲本菌株一样生长，这表明观察到的生长缺陷是细胞内的，不是由第二位点突变或缺乏扩散因子引起的。然而，LuxS/AI-2系统似乎对金黄色葡萄球菌RN6390B在上皮细胞内生长的整体适应性没有贡献：野生型和LuxS突变体在被MAC-T细胞内化后表现出非常相似的生长模式。
The function of AI-2 in many bacteria and the physiological role of LuxS, the enzyme responsible for its production, remain matters of debate. Here, we show that in Staphylococcus aureus the luxS gene forms a monocistronic transcriptional unit under the control of a sigma(70)-dependent promoter. The gene was transcribed throughout growth under a variety of conditions, including intracellular growth in MAC-T cells. AI-2 was produced in rich media under aerobic and anaerobic conditions, peaking during the transition to stationary phase, but was hardly detectable in a sulfur-limited defined medium. In the presence of glucose or under anaerobic conditions, cultures retained considerable AI-2 activity after entry into stationary phase. Inactivation of luxS in various S. aureus strains did not affect virulence-associated traits, such as production of hemolysins and extracellular proteases, biofilm formation, and the agr signaling system. Conversely, AI-2 production remained unchanged in an agr mutant. However, luxS mutants grown in a sulfur-limited defined medium exhibited a growth defect. When grown together with the wild type in mixed culture, luxS mutants of various S. aureus strains showed reduced ability to compete for growth under these conditions. In contrast, a complemented luxS mutant grew as well as the parent strain, suggesting that the observed growth defect was of an intracellular nature and had not been caused by either second-site mutations or the lack of a diffusible factor. However, the LuxS/AI-2 system does not appear to contribute to the overall fitness of S. aureus RN6390B during intracellular growth in epithelial cells: the wild type and a luxS mutant showed very similar growth patterns after their internalization by MAC-T cells.