Novel insights into biosynthesis and uptake of rhamnolipids and their precursors

作者：Andreas Wittgens, Filip Kovačić, Markus Michael Müller, Melanie Gerlitzki, Beatrix Santiago‐Schübel, Diana Hofmann, Till Tiso, Lars M. Blank, Marius Henkel, Rudolf Hausmann, Christoph Syldatk, Susanne Wilhelm, Frank Rosenau · 发表于：Applied Microbiology and Biotechnology · 年份：2016 · DOI：10.1007/s00253-016-8041-3 · 被引用次数：132 · 研究领域：Microbial bioremediation and biosurfactants、Bacterial Genetics and Biotechnology、Glycosylation and Glycoproteins Research

The human pathogenic bacterium Pseudomonas aeruginosa produces rhamnolipids, glycolipids with functions for bacterial motility, biofilm formation, and uptake of hydrophobic substrates. Rhamnolipids represent a chemically heterogeneous group of secondary metabolites composed of one or two rhamnose molecules linked to one or mostly two 3-hydroxyfatty acids of various chain lengths. The biosynthetic pathway involves rhamnosyltransferase I encoded by the rhlAB operon, which synthesizes 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) followed by their coupling to one rhamnose moiety. The resulting mono-rhamnolipids are converted to di-rhamnolipids in a third reaction catalyzed by the rhamnosyltransferase II RhlC. However, the mechanism behind the biosynthesis of rhamnolipids containing only a single fatty acid is still unknown. To understand the role of proteins involved in rhamnolipid biosynthesis the heterologous expression of rhl-genes in non-pathogenic Pseudomonas putida KT2440 strains was used in this study to circumvent the complex quorum sensing regulation in P. aeruginosa. Our results reveal that RhlA and RhlB are independently involved in rhamnolipid biosynthesis and not in the form of a RhlAB heterodimer complex as it has been previously postulated. Furthermore, we demonstrate that mono-rhamnolipids provided extracellularly as well as HAAs as their precursors are generally taken up into the cell and are subsequently converted to di-rhamnolipids by P. putida and the native ...