Effects of osmotic stress on rhamnolipid synthesis and time-course production of cell-to-cell signal molecules by Pseudomonas aeruginosa.
Effects of osmotic stress on rhamnolipid synthesis and time-course production of cell-to-cell signal molecules by Pseudomonas aeruginosa.
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DOI：
10.2174/1874285800903010128
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发表时间：
2009-08-13
期刊：
影响因子：
--
通讯作者：
Dufour A
中科院分区：
文献类型：
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作者：
Bazire A;Diab F;Taupin L;Rodrigues S;Jebbar M;Dufour A
铜绿假单胞菌对生物表面活性物质鼠李糖脂的生物合成依赖于LASRI和RhLRI两个分级群体感应系统，它们分别合成和感应信号分子N-(3-氧代碘正十一酰)-L-高丝氨酸内酯(3OC12-HSL)和N-丁酰基-L-高丝氨酸内酯(C4-HSL)。假单胞菌喹诺酮信号(PQs)是连接这两个系统的第三个细胞间信号分子，其前体2-庚基-4-喹诺酮(HHQ)也构成信号。测定了在PPGAS培养液中生长过程中信号分子和鼠李糖脂产生的年表。高渗条件(0.5M氯化钠)中度影响生长，并导致胞内亲和溶质的积累。信号分子的产生延迟，除HHQ的最高浓度升高外，其余信号分子的最高浓度比无盐PPGAS低2.5~5倍。氯化钠的存在阻止了鼠李糖脂的合成。当渗透保护剂甘氨酸甜菜碱加入到PPGAS/NaC l培养基中时，甜菜碱被细胞输入而不被代谢。这没有改善生长，但重新建立了HSL和HHQ积累的时间进程，并完全或部分恢复了HSL和PQS水平。它还部分恢复了鼠李糖脂的生产。编码HSL、PQS和鼠李糖脂生物合成相关酶的mRNAs的定量证实了高渗胁迫和甘氨酸甜菜碱在基因表达水平上的影响。
Biosynthesis of biosurfactant rhamnolipids by Pseudomonas aeruginosa depends on two hierarchical quorum sensing systems, LasRI and RhlRI, which synthesize and sense the signal molecules N-(3-oxododecanoyl)-L-homoserine lactone (3OC12-HSL) and N-butyryl-L-homoserine lactone (C4-HSL), respectively. The Pseudomonas Quinolone Signal (PQS) is a third cell-to-cell signal molecule connecting these two systems, and its precursor, 2-heptyl-4-quinolone (HHQ), also constitutes a signal. The chronology of the production of signal molecules and rhamnolipids was determined during growth in PPGAS medium. Hyperosmotic condition (0.5 M NaCl) moderately affected growth, and led to intra-cellular accumulation of compatible solutes. Production of signal molecules was delayed and their highest concentrations were 2.5 to 5 fold lower than in NaCl-free PPGAS, except for HHQ, the highest concentration of which was increased. The presence of NaCl prevented rhamnolipid synthesis. When the osmoprotectant glycine betaine was added to PPGAS/NaCl medium, it was imported by the cells without being metabolized. This did not improve growth, but reestablished the time-courses of HSL and HHQ accumulation and fully or partially restored the HSL and PQS levels. It also partially restored rhamnolipid production. Quantification of mRNAs encoding enzymes involved in HSL, PQS, and rhamnolipid biosyntheses confirmed the effect of hyperosmotic stress and glycine betaine at the gene expression level.