Koch A K, Käppeli O, Fiechter A, Reiser J
Institute for Biotechnology, ETH-Hönggerberg, Zürich, Switzerland.
J Bacteriol. 1991 Jul;173(13):4212-9. doi: 10.1128/jb.173.13.4212-4219.1991.
We isolated transposon Tn5-GM-induced mutants of Pseudomonas aeruginosa PG201 that were unable to grow in minimal media containing hexadecane as a carbon source. Some of these mutants lacked extracellular rhamnolipids, as shown by measuring the surface and interfacial tensions of the cell culture supernatants. Furthermore, the concentrated culture media of the mutant strains were tested for the presence of rhamnolipids by thin-layer chromatography and for rhamnolipid activities, including hemolysis and growth inhibition of Bacillus subtilis. Mutant 65E12 was unable to produce extracellular rhamnolipids under any of the conditions tested, lacked the capacity to take up 14C-labeled hexadecane, and did not grow in media containing individual alkanes with chain lengths ranging from C12 to C19. However, growth on these alkanes and uptake of [14C]hexadecane were restored when small amounts of purified rhamnolipids were added to the cultures. Mutant 59C7 was unable to grow in media containing hexadecane, nor was it able to take up [14C]hexadecane. The addition of small amounts of rhamnolipids restored growth on alkanes and [14C]hexadecane uptake. In glucose-containing media, however, mutant 59C7 produced rhamnolipids at levels about twice as high as those of the wild-type strain. These results show that rhamnolipids play a major role in hexadecane uptake and utilization by P. aeruginosa.
我们分离出了铜绿假单胞菌PG201的转座子Tn5 - GM诱导突变体，这些突变体无法在以十六烷作为碳源的基本培养基中生长。通过测量细胞培养上清液的表面张力和界面张力发现，其中一些突变体缺乏细胞外鼠李糖脂。此外，通过薄层色谱法检测突变菌株的浓缩培养基中是否存在鼠李糖脂，并检测其鼠李糖脂活性，包括溶血和对枯草芽孢杆菌的生长抑制作用。突变体65E12在任何测试条件下都无法产生细胞外鼠李糖脂，缺乏摄取14C标记十六烷的能力，并且在含有链长从C12到C19的单烷烃的培养基中不能生长。然而，当向培养物中添加少量纯化的鼠李糖脂时，其在这些烷烃上的生长以及对[14C]十六烷的摄取得以恢复。突变体59C7无法在含有十六烷的培养基中生长，也不能摄取[14C]十六烷。添加少量鼠李糖脂可恢复其在烷烃上的生长以及[14C]十六烷的摄取。然而，在含葡萄糖的培养基中，突变体59C7产生的鼠李糖脂水平约为野生型菌株的两倍。这些结果表明，鼠李糖脂在铜绿假单胞菌摄取和利用十六烷过程中起主要作用。
