Huber Birgit, Riedel Kathrin, Hentzer Morten, Heydorn Arne, Gotschlich Astrid, Givskov Michael, Molin Søren, Eberl Leo
Lehrstuhl für Mikrobiologie, Technische Universität München, Am Hochanger 4, 85350 Freising, Germany1.
Department of Microbiology, DTU, Building 301, 2800 Lyngby, Denmark2.
Microbiology (Reading). 2001 Sep;147(Pt 9):2517-2528. doi: 10.1099/00221287-147-9-2517.
Burkholderia cepacia and Pseudomonas aeruginosa often co-exist as mixed biofilms in the lungs of patients suffering from cystic fibrosis (CF). Here, the isolation of random mini-Tn5 insertion mutants of B. cepacia H111 defective in biofilm formation on an abiotic surface is reported. It is demonstrated that one of these mutants no longer produces N-acylhomoserine lactones (AHLs) due to an inactivation of the cepR gene. cepR and the cepI AHL synthase gene together constitute the cep quorum-sensing system of B. cepacia. By using a gene replacement method, two defined mutants, H111-I and H111-R, were constructed in which cepI and cepR, respectively, had been inactivated. These mutants were used to demonstrate that biofilm formation by B. cepacia H111 requires a functional cep quorum-sensing system. A detailed quantitative analysis of the biofilm structures formed by wild-type and mutant strains suggested that the quorum-sensing system is not involved in the regulation of initial cell attachment, but rather controls the maturation of the biofilm. Furthermore, it is shown that B. cepacia is capable of swarming motility, a form of surface translocation utilized by various bacteria to rapidly colonize appropriate substrata. Evidence is provided that swarming motility of B. cepacia is quorum-sensing-regulated, possibly through the control of biosurfactant production. Complementation of the cepR mutant H111-R with different biosurfactants restored swarming motility while biofilm formation was not significantly increased. This result suggests that swarming motility per se is not essential for biofilm formation on abiotic surfaces.
洋葱伯克霍尔德菌和铜绿假单胞菌常以混合生物膜的形式共存于囊性纤维化（CF）患者的肺部。在此，报道了从洋葱伯克霍尔德菌H111中分离出在非生物表面形成生物膜有缺陷的随机mini-Tn5插入突变体。结果表明，其中一个突变体由于cepR基因失活而不再产生N-酰基高丝氨酸内酯（AHLs）。cepR和cepI AHL合酶基因共同构成了洋葱伯克霍尔德菌的cep群体感应系统。通过基因置换方法，构建了两个确定的突变体H111-I和H111-R，其中cepI和cepR分别被失活。这些突变体用于证明洋葱伯克霍尔德菌H111形成生物膜需要功能性的cep群体感应系统。对野生型和突变株形成的生物膜结构进行的详细定量分析表明，群体感应系统不参与初始细胞附着的调节，而是控制生物膜的成熟。此外，研究表明洋葱伯克霍尔德菌具有群体游动能力，这是多种细菌用于快速定殖于合适底物的一种表面移位形式。有证据表明，洋葱伯克霍尔德菌的群体游动能力受群体感应调节，可能是通过控制生物表面活性剂的产生来实现的。用不同的生物表面活性剂对cepR突变体H111-R进行互补可恢复群体游动能力，而生物膜形成没有显著增加。这一结果表明，群体游动本身对于在非生物表面形成生物膜并非必不可少。
