IBB-Institute for Biotechnology and Bioengineering, Center for Biological and Chemical Engineering, Instituto Superior Técnico, Lisbon 1049-001, Portugal.
Microbial Evolutionary Genomics Group, CNRS URA2171, Institute Pasteur, F-75015 Paris, France.
Microbiology (Reading). 2010 Apr;156(Pt 4):1084-1096. doi: 10.1099/mic.0.032623-0. Epub 2009 Dec 17.
Members of the Burkholderia cepacia complex (Bcc) are respiratory pathogens in patients with cystic fibrosis (CF). Close repetitive DNA sequences often associate with surface antigens to promote genetic variability in pathogenic bacteria. The genome of Burkholderia cenocepacia J2315, a CF isolate belonging to the epidemic lineage Edinburgh-Toronto (ET-12), was analysed for the presence of close repetitive DNA sequences. Among the 422 DNA close repeats, 45 genes potentially involved in virulence were identified and grouped into 12 classes; of these, 13 genes were included in the antigens class. Two trimeric autotransporter adhesins (TAA) among the 13 putative antigens are absent from the other Burkholderia genomes and are clustered downstream of the cci island that is a marker for transmissible B. cenocepacia strains. This cluster contains four adhesins, one outer-membrane protein, one sensor histidine kinase and two transcriptional regulators. By using PCR, we analysed three genes among 47 Bcc isolates to determine whether the cluster was conserved. These three genes were present in the isolates of the ET-12 lineage but absent in all the other members. Furthermore, the BCAM0224 gene was exclusively detected in this epidemic lineage and may serve as a valuable new addition to the field of Bcc diagnostics. The BCAM0224 gene encodes a putative TAA that demonstrates adhesive properties to the extracellular matrix protein collagen type I. Quantitative real-time PCR analysis indicated that BCAM0224 gene expression occurred preferentially for cells grown under high osmolarity, oxygen-limited conditions and oxidative stress. Inactivation of BCAM0224 in B. cenocepacia attenuates the ability of the mutant to promote cell adherence in vitro and impairs the overall bacterial virulence against Galleria mellonella as a model of infection. Together, our data show that BCAM0224 from B. cenocepacia J2315 represents a new collagen-binding TAA with no bacterial orthologues which has an important role in cellular adhesion and virulence.
伯克霍尔德氏菌复合群(Bcc)的成员是囊性纤维化(CF)患者的呼吸道病原体。紧密重复的 DNA 序列通常与表面抗原相关联,以促进病原菌的遗传变异。属于流行谱系爱丁堡-多伦多(ET-12)的 CF 分离株 Burkholderia cenocepacia J2315 的基因组被分析是否存在紧密重复的 DNA 序列。在 422 个 DNA 紧密重复中,鉴定出 45 个可能与毒力有关的基因,并分为 12 类;其中 13 个基因属于抗原类。在这 13 个假定抗原中,有两个三聚体自转运黏附素(TAA)不存在于其他 Burkholderia 基因组中,而是聚集在 cci 岛的下游,cci 岛是可传播的 B. cenocepacia 菌株的标志。该簇包含四个黏附素、一个外膜蛋白、一个传感器组氨酸激酶和两个转录调节剂。通过使用 PCR,我们分析了 47 个 Bcc 分离株中的三个基因,以确定该簇是否保守。这些基因存在于 ET-12 谱系的分离株中,但不存在于所有其他成员中。此外,BCAM0224 基因仅在这个流行谱系中被检测到,可能是 Bcc 诊断领域的一个有价值的新补充。BCAM0224 基因编码一种假定的 TAA,它对细胞外基质蛋白胶原蛋白 I 具有黏附特性。定量实时 PCR 分析表明,BCAM0224 基因的表达优先发生在高渗透压、氧气限制和氧化应激条件下生长的细胞中。BCAM0224 在 B. cenocepacia 中的失活削弱了突变体在体外促进细胞黏附的能力,并损害了细菌对金龟子幼虫作为感染模型的整体毒力。总之,我们的数据表明,B. cenocepacia J2315 的 BCAM0224 代表了一种新的胶原蛋白结合 TAA,没有细菌直系同源物,它在细胞黏附和毒力中起着重要作用。