Li Yi, Petrova Olga E, Su Shengchang, Lau Gee W, Panmanee Warunya, Na Renuka, Hassett Daniel J, Davies David G, Sauer Karin
Department of Biological Sciences, Binghamton University, Binghamton, New York, United States of America.
Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
PLoS Pathog. 2014 Jun 5;10(6):e1004168. doi: 10.1371/journal.ppat.1004168. eCollection 2014 Jun.
The human pathogen Pseudomonas aeruginosa is capable of causing both acute and chronic infections. Differences in virulence are attributable to the mode of growth: bacteria growing planktonically cause acute infections, while bacteria growing in matrix-enclosed aggregates known as biofilms are associated with chronic, persistent infections. While the contribution of the planktonic and biofilm modes of growth to virulence is now widely accepted, little is known about the role of dispersion in virulence, the active process by which biofilm bacteria switch back to the planktonic mode of growth. Here, we demonstrate that P. aeruginosa dispersed cells display a virulence phenotype distinct from those of planktonic and biofilm cells. While the highest activity of cytotoxic and degradative enzymes capable of breaking down polymeric matrix components was detected in supernatants of planktonic cells, the enzymatic activity of dispersed cell supernatants was similar to that of biofilm supernatants. Supernatants of non-dispersing ΔbdlA biofilms were characterized by a lack of many of the degradative activities. Expression of genes contributing to the virulence of P. aeruginosa was nearly 30-fold reduced in biofilm cells relative to planktonic cells. Gene expression analysis indicated dispersed cells, while dispersing from a biofilm and returning to the single cell lifestyle, to be distinct from both biofilm and planktonic cells, with virulence transcript levels being reduced up to 150-fold compared to planktonic cells. In contrast, virulence gene transcript levels were significantly increased in non-dispersing ΔbdlA and ΔdipA biofilms compared to wild-type planktonic cells. Despite this, bdlA and dipA inactivation, resulting in an inability to disperse in vitro, correlated with reduced pathogenicity and competitiveness in cross-phylum acute virulence models. In contrast, bdlA inactivation rendered P. aeruginosa more persistent upon chronic colonization of the murine lung, overall indicating that dispersion may contribute to both acute and chronic infections.
人类病原体铜绿假单胞菌能够引发急性和慢性感染。毒力差异归因于生长方式：浮游生长的细菌引发急性感染，而在被称为生物膜的基质包裹聚集体中生长的细菌则与慢性持续性感染相关。虽然浮游生长和生物膜生长方式对毒力的影响现已被广泛接受，但关于细菌从生物膜中重新转变为浮游生长方式的扩散过程在毒力方面所起的作用却知之甚少。在此，我们证明铜绿假单胞菌的扩散细胞表现出一种与浮游细胞和生物膜细胞不同的毒力表型。虽然在浮游细胞的上清液中检测到能够分解聚合基质成分的细胞毒性和降解酶的最高活性，但扩散细胞上清液的酶活性与生物膜上清液相似。未扩散的ΔbdlA生物膜的上清液表现为缺乏许多降解活性。相对于浮游细胞，参与铜绿假单胞菌毒力的基因在生物膜细胞中的表达降低了近30倍。基因表达分析表明，扩散细胞在从生物膜扩散并回归单细胞生活方式时，与生物膜细胞和浮游细胞都不同，其毒力转录水平与浮游细胞相比降低了多达150倍。相比之下，与野生型浮游细胞相比，在未扩散的ΔbdlA和ΔdipA生物膜中毒力基因转录水平显著增加。尽管如此，bdlA和dipA的失活导致体外无法扩散，这与跨门急性毒力模型中致病性和竞争力的降低相关。相反，bdlA失活使铜绿假单胞菌在小鼠肺部慢性定植时更具持久性，总体表明扩散可能对急性和慢性感染都有影响。
