Timing and localization of rhamnolipid synthesis gene expression in Pseudomonas aeruginosa biofilms
Timing and localization of rhamnolipid synthesis gene expression in Pseudomonas aeruginosa biofilms
复制标题
DOI：
10.1128/jb.187.1.37-44.2005
复制
发表时间：
2005-01-01
影响因子：
3.2
通讯作者：
Greenberg, EP
中科院分区：
文献类型：
--
作者：
Lequette, Y;Greenberg, EP
铜绿假单胞菌生物被膜可形成蘑菇状结构，其茎和帽由离散的细胞亚群组成。自产鼠李糖脂表面活性剂已被证明在蘑菇状结构的发展中起着重要作用。鼠李糖脂的合成需要受群体感应控制的rhlAB操纵子。我们已经在铜绿假单胞菌基因组中的一个中性位置引入了重组人乳糖体蛋白A-GFP融合，以研究鼠李糖脂生物膜中重组人乳糖体B启动子的活性。RhlA-GFP融合蛋白在生物膜中的表达需要群体感应信号丁酰高丝氨酸内酯，但表达还需要其他因素。在生物膜发育的早期，即使在添加丁酰高丝氨酸内酯的情况下，rhlA-GFP的表达也很低。融合的表达在形成深度为20微米的微集落后变得明显，RFP或荧光染料的差异标记表明，rh lA-GFP优先在成熟蘑菇的茎中表达，而不是在菌帽中表达。在生物膜生长培养基中添加丁酰高丝氨酸内酯对rhlA-GFP的表达模式影响不大。我们认为鼠李糖脂的合成发生在茎形成后的生物膜中，但在蘑菇状结构中覆盖之前。Rh lAB的差异表达可能在正常生物膜结构的形成中起作用。
Pseudomonas aeruginosa biofilms can develop mushroom-like structures with stalks and caps consisting of discrete subpopulations of cells. Self-produced rhamnolipid surfactants have been shown to be important in development of the mushroom-like structures. The quorum-sensing-controlled rhlAB operon is required for rhamnolipid synthesis. We have introduced an rhlA-gfp fusion into a neutral site in the P. aeruginosa genome to study rhLAB promoter activity in rhamnolipid-producing biofilms. Expression of the rhlA-gfp fusion in biofilms requires the quorum-sensing signal butanoyl-homoserine lactone, but other factors are also required for expression. Early in biofilm development rhlA-gfp expression is low, even in the presence of added butanoyl-homoserine lactone. Expression of the fusion becomes apparent after microcolonies with a depth of > 20 mum have formed and, as shown by differential labeling with rfp or fluorescent dyes, rhlA-gfp is preferentially expressed in the stalks rather than the caps of mature mushrooms. The rhlA-gfp expression pattern is not greatly influenced by addition of butanoyl-homoserine lactone to the biofilm growth medium. We propose that rhamnolipid synthesis occurs in biofilms after stalks have formed but prior to capping in the mushroom-like structures. The differential expression of rhlAB may play a role in the development of normal biofilm architecture.