Center for Biological and Chemical Engineering, Instituto Superior Técnico, Lisbon, Portugal.
PLoS One. 2012;7(7):e41747. doi: 10.1371/journal.pone.0041747. Epub 2012 Jul 25.
Burkholderia cepacia complex (Bcc) bacteria are a problematic group of microorganisms causing severe infections in patients with Cystic Fibrosis. In early stages of infection, Bcc bacteria must be able to adhere to and colonize the respiratory epithelium. Although this is not fully understood, this primary stage of infection is believed to be in part mediated by a specific type of adhesins, named trimeric autotransporter adhesins (TAAs). These homotrimeric proteins exist on the surface of many gram negative pathogens and often mediate a number of critical functions, including biofilm formation, serum resistance and adherence to an invasion of host cells. We have previously identified in the genome of the epidemic clinical isolate B. cenocepacia J2315, a novel cluster of genes putatively encoding three TAAs (BCAM0219, BCAM0223 and BCAM0224). In this study, the genomic organization of the TAA cluster has been determined. To further address the direct role of the putative TAA BCAM0223 in B. cenocepacia pathogenicity, an isogenic mutant was constructed via insertional inactivation. The BCAM0223::Tp mutant is deficient in hemagglutination, affected in adherence to vitronectin and in biofilm formation and showed attenuated virulence in the Galleria mellonella model of infection. Moreover, the BCAM0223::Tp mutant also showed a significant reduction in its resistance to human serum as well as in adherence, but not in invasion of, cultured human bronchial epithelial cells. Altogether these results demonstrate that the BCAM0223 protein is a multifunctional virulence factor that may contribute to the pathogenicity of B. cenocepacia.
洋葱伯克霍尔德氏菌复合体（Bcc）是一组引起囊性纤维化患者严重感染的问题微生物。在感染的早期阶段，Bcc 细菌必须能够附着并定殖在呼吸道上皮。尽管这尚未完全了解，但人们认为这种感染的初始阶段部分是由一种特定类型的黏附素介导的，这种黏附素名为三聚体自转运黏附素（TAAs）。这些三聚体蛋白存在于许多革兰氏阴性病原体的表面，通常介导多种关键功能，包括生物膜形成、血清抗性和对宿主细胞的附着。我们之前在流行临床分离株洋葱伯克霍尔德氏菌 J2315 的基因组中鉴定了一个假定编码三个 TAAs（BCAM0219、BCAM0223 和 BCAM0224）的新基因簇。在这项研究中，确定了 TAA 簇的基因组组织。为了进一步确定假定的 TAA BCAM0223 在洋葱伯克霍尔德氏菌致病性中的直接作用，通过插入失活构建了一个同源突变体。BCAM0223::Tp 突变体在血凝、对玻连蛋白的附着以及生物膜形成方面均存在缺陷，并且在感染蜡螟的模型中表现出毒力减弱。此外，BCAM0223::Tp 突变体对人血清的抗性以及附着能力（但不包括入侵）也显著降低，但对培养的人支气管上皮细胞的附着和入侵能力没有影响。总之，这些结果表明，BCAM0223 蛋白是一种多功能毒力因子，可能有助于洋葱伯克霍尔德氏菌的致病性。
