Pseudomonas strains produce rhamnolipid mixtures (RLs) that generally consist of one or two molecules of rhamnose linked to one or two molecules of 3-hydroxyalkanoic acid. This study evaluates carbon source effects (glycerol, glucose, myristic acid, and Brassica carinata oil) on the synthesis of monorhamnolipids (mono-RLs) versus dirhamnolipids (di-RLs) in a human isolate of Pseudomonas aeruginosa PAL05. Spectrophotometry, an emulsifying index (E24) test, and an orcinol assay confirmed the production of RLs by PAL05. Purified RLs were characterized by 1H NMR analysis. PAL05 primarily produces mono-RLs when provided carbon sources containing long chain fatty acids (FAs) (myristic acid and B. carinata oil) and di-RLs when provided glycerol or glucose. qRT-PCR analysis showed that delayed expression of rhlC occurred when B. carinata oil was used, but not glycerol, glucose, or myristic acid. Our data show that the carbon source influenced the transcriptional expression of the rhlC gene and, consequently, the predominance of mono-RLs or di-RLs in PAL05 cultures.

中文翻译：

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碳源对铜绿假单胞菌 L05（一种新的人类呼吸道分离株）产生的单/二鼠李糖脂比的影响

假单胞菌菌株产生鼠李糖脂混合物 (RL)，其通常由一或两分子鼠李糖与一或两分子 3-羟基链烷酸连接而成。本研究评估了碳源（甘油、葡萄糖、肉豆蔻酸和芸苔油）对铜绿假单胞菌 PAL05 人类分离株中单鼠李糖脂 (mono-RLs) 与 dirhamnolipids (di-RLs) 合成的影响。分光光度法、乳化指数 (E24) 测试和地黄酚测定证实了 PAL05 产生的 RL。纯化的 RL 通过 1 H NMR 分析表征。当提供含有长链脂肪酸 (FA)（肉豆蔻酸和 B. carinata 油）的碳源时，PAL05 主要产生单 RLs，当提供甘油或葡萄糖时产生 di-RLs。qRT-PCR 分析表明，当使用 B. carinata 油时，rhlC 的表达延迟，但不是甘油、葡萄糖或肉豆蔻酸。我们的数据表明，碳源影响了 rhlC 基因的转录表达，因此影响了 PAL05 培养物中单 RL 或双 RL 的优势。