de Weert Sandra, Dekkers Linda C, Bitter Wilbert, Tuinman Sietske, Wijfjes André H M, van Boxtel Ria, Lugtenberg Ben J J
Institute of Biology, Leiden University, AL Leiden, The Netherlands.
FEMS Microbiol Ecol. 2006 Nov;58(2):205-13. doi: 10.1111/j.1574-6941.2006.00158.x.
Pseudomonas fluorescens strain PCL1210, a competitive tomato root tip colonization mutant of the efficient root colonizing wild type strain WCS365, is impaired in the two-component sensor-response regulator system ColR/ColS. Here we show that a putative methyltransferase/wapQ operon is located downstream of colR/colS and that this operon is regulated by ColR/ColS. Since wapQ encodes a putative lipopolysaccharide (LPS) phosphatase, the possibility was studied that the integrity of the outer membrane of PCL1210 was altered. Indeed, it was shown that mutant PCL1210 is more resistant to various chemically unrelated antibiotics which have to pass the outer membrane for their action. In contrast, the mutant is more sensitive to the LPS-binding antibiotic polymyxin B. Mutant PCL1210 loses growth in competition with its wild type when grown in tomato root exudate. Mutants in the methyltransferase/wapQ operon are also altered in their outer membrane permeability and are defective in competitive tomato root tip colonization. A model for the altered outer membrane of PCL1210 is discussed.
荧光假单胞菌菌株PCL1210是高效定殖于根部的野生型菌株WCS365的一个具有竞争性的番茄根尖定殖突变体，它在双组分传感-反应调节系统ColR/ColS中存在缺陷。在此我们表明，一个假定的甲基转移酶/wapQ操纵子位于colR/colS的下游，并且该操纵子受ColR/ColS调控。由于wapQ编码一种假定的脂多糖（LPS）磷酸酶，因此研究了PCL1210外膜完整性发生改变的可能性。确实，已表明突变体PCL1210对各种化学性质不相关的抗生素具有更强的抗性，这些抗生素必须穿过外膜才能发挥作用。相反，该突变体对LPS结合抗生素多粘菌素B更敏感。当在番茄根分泌物中生长时，突变体PCL1210在与野生型的竞争中失去生长能力。甲基转移酶/wapQ操纵子中的突变体在外膜通透性方面也发生了改变，并且在竞争性番茄根尖定殖方面存在缺陷。本文讨论了PCL1210外膜改变的模型。
