Mikkelsen H, Bond N J, Skindersoe M E, Givskov M, Lilley K S, Welch M
Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK.
ChemoMetec A/S, Gydevang 43, DK-3450 Alleroed, Denmark.
Microbiology (Reading). 2009 Mar;155(Pt 3):687-698. doi: 10.1099/mic.0.025551-0.
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes acute and chronic infections in immunocompromised individuals. It is also a model organism for bacterial biofilm formation. Acute infections are often associated with planktonic or free-floating cells, high virulence and fast growth. Conversely, chronic infections are often associated with the biofilm mode of growth, low virulence and slow growth that resembles that of planktonic cells in stationary phase. Biofilm formation and type III secretion have been shown to be reciprocally regulated, and it has been suggested that factors related to acute infection may be incompatible with biofilm formation. In a previous proteomic study of the interrelationships between planktonic cells, colonies and continuously grown biofilms, we showed that biofilms under the growth conditions applied are more similar to planktonic cells in exponential phase than to those in stationary phase. In the current study, we investigated how these conditions influence the production of virulence factors using a transcriptomic approach. Our results show that biofilms express the type III secretion system, whereas planktonic cells do not. This was confirmed by the detection of PcrV in the cellular and secreted fractions of biofilms, but not in those of planktonic cells. We also detected the type III effector proteins ExoS and ExoT in the biofilm effluent, but not in the supernatants of planktonic cells. Biofilm formation and type III secretion are therefore not mutually exclusive in P. aeruginosa, and biofilms could play a more active role in virulence than previously thought.
铜绿假单胞菌是一种革兰氏阴性机会致病菌，可在免疫功能低下的个体中引起急性和慢性感染。它也是细菌生物膜形成的模式生物。急性感染通常与浮游或自由漂浮的细胞、高毒力和快速生长有关。相反，慢性感染通常与生物膜生长模式、低毒力和类似于稳定期浮游细胞的缓慢生长有关。生物膜形成和III型分泌已被证明是相互调节的，并且有人提出与急性感染相关的因素可能与生物膜形成不相容。在先前一项关于浮游细胞、菌落和持续生长的生物膜之间相互关系的蛋白质组学研究中，我们表明在所应用的生长条件下，生物膜与指数期的浮游细胞比与稳定期的浮游细胞更相似。在当前的研究中，我们使用转录组学方法研究了这些条件如何影响毒力因子的产生。我们的结果表明，生物膜表达III型分泌系统，而浮游细胞则不表达。通过在生物膜的细胞和分泌部分中检测到PcrV，但在浮游细胞的部分中未检测到，证实了这一点。我们还在生物膜流出物中检测到III型效应蛋白ExoS和ExoT，但在浮游细胞的上清液中未检测到。因此，生物膜形成和III型分泌在铜绿假单胞菌中并非相互排斥，并且生物膜在毒力方面可能比以前认为的发挥更积极的作用。
