Gonyar Laura A, Fankhauser Sarah C, Goldberg Joanna B
Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA.
Environ Microbiol Rep. 2015 Apr;7(2):180-7. doi: 10.1111/1758-2229.12217. Epub 2014 Dec 17.
The Burkholderia cepacia complex (Bcc) is a group of Gram-negative bacilli that are ubiquitous in the environment and have emerged over the past 30 years as opportunistic pathogens in immunocompromised populations, specifically individuals with cystic fibrosis (CF) and chronic granulomatous disease. This complex of at least 18 distinct species is phenotypically and genetically diverse. One phenotype observed in a subset of Burkholderia cenocepacia (a prominent Bcc pathogen) isolates is the ability to produce a melanin-like pigment. Melanins have antioxidant properties and have been shown to act as virulence factors allowing pathogens to resist killing by the host immune system. The melanin-like pigment expressed by B. cenocepacia is produced through tyrosine catabolism, specifically through the autoxidation and polymerization of homogentisate. Burkholderia cenocepacia J2315 is a CF clinical isolate that displays a pigmented phenotype when grown under normal laboratory conditions. We examined the amino acid sequences of critical enzymes in the melanin synthesis pathway in pigmented and non-pigmented Bcc isolates, and found that an amino acid substitution of glycine for arginine at amino acid 378 in homogentisate 1,2-dioxygenase correlated with pigment production; we identify this as one mechanism for expression of pigment in Bcc isolates.
洋葱伯克霍尔德菌复合体(Bcc)是一组革兰氏阴性杆菌,在环境中广泛存在,并且在过去30年中已成为免疫功能低下人群(特别是囊性纤维化(CF)患者和慢性肉芽肿病患者)中的机会性病原体。这个由至少18个不同物种组成的复合体在表型和基因上具有多样性。在洋葱伯克霍尔德菌(一种主要的Bcc病原体)的一部分分离株中观察到的一种表型是产生类黑色素的能力。黑色素具有抗氧化特性,并已被证明可作为毒力因子,使病原体能够抵抗宿主免疫系统的杀伤。洋葱伯克霍尔德菌表达的类黑色素是通过酪氨酸分解代谢产生的,特别是通过尿黑酸的自动氧化和聚合作用。洋葱伯克霍尔德菌J2315是一种CF临床分离株,在正常实验室条件下生长时表现出色素沉着表型。我们检查了有色素和无色素的Bcc分离株中黑色素合成途径关键酶的氨基酸序列,发现尿黑酸1,2-双加氧酶第378位氨基酸处的精氨酸被甘氨酸取代与色素产生相关;我们将此确定为Bcc分离株中色素表达的一种机制。