The interface between metabolism and virulence in environmental pathogens

环境病原体是生活在人类宿主之外的微生物，但可以进入人体并导致疾病。一个值得注意的例子是洋葱伯克霍尔德氏菌复合体(BCC)，这是一组革兰氏阴性细菌，其特征是多功能分解代谢，能够在不同的环境中定居，并与多种宿主相联系，包括患有遗传性疾病囊性纤维化(CF)的人类。在我之前的NSERC发现计划中，我在氨基酸消耗和细菌毒力之间建立了一个新的联系。我发现苯丙氨酸分解代谢的中间产物苯乙酸(PAA)调节BCC群体感应(QS)反应，进而调节毒力。NSERC的这项研究计划将扩展在感染条件下氨基酸分解代谢的研究，重点放在PAA介导的QS调节的生物学意义上。*我的实验室将使用分子生物学工具和结构分析来研究PAA和其他苯丙氨酸分解代谢中间产物是否与群体感应调节因子结合，以及已发现的相互作用是否改变了它们对毒力基因的调节作用。盲肠弯曲杆菌是基底细胞癌的一种，可在肺脏富含氨基酸的微氧粘液中生长，并形成慢性感染。为了解决PAA相关毒力下调的生物学意义，我们将研究苯丙氨酸降解在低氧条件下对QS介导的致病性的贡献，在低氧条件下，BCC中PAA的降解可能被取消。根结线虫能够在植物模型拟南芥中引起感染，允许在植物-细菌相互作用期间探索苯丙氨酸和PAA的新陈代谢。PAA是一种植物激素，可能作为植物防御机制的一部分在植物中下调。为了探索是否能产生类似PAA的分子来增强植物对感染的敏感性，我们将使用拟南芥的寄主模型，并监测在PAA分解代谢的不同阶段被阻断的突变体感染植物的病情进展。本研究将建立PAA分解代谢调节QS的分子基础，阐明两个保守的细菌特征之间的新联系。基底细胞癌的不同致病相互作用允许使用植物和动物模型。因此，我们的发现将对与动物、人类和植物相关的微生物相互作用过程中的微生物代谢产生广泛的影响。功能基因组学、化学和分子生物学之间的交叉反馈将为工业界和学术界高度需求的跨学科研究提供几个培训机会。识别将营养使用与QS联系起来的分子机制将揭示干预成分可能成为治疗或生物技术干预的目标。***********

Environmental pathogens are microorganisms that live outside the human host but can gain access to the human body and cause disease. A remarkable example is the Burkholderia cepacia complex (Bcc), a group of Gram negative bacteria characterized by versatile catabolism, the ability to colonize diverse environments and associate with several hosts, including humans with the genetic disease cystic fibrosis (CF). In my previous NSERC Discovery program, I established a novel association between amino acid consumption and bacterial virulence. I discovered that an intermediate of phenylalanine catabolism, phenylacetic acid (PAA), modulates the Bcc quorum sensing (QS) response, which in turn regulates virulence. This NSERC research program will expand on amino acid catabolism during infection conditions with a focus on the biological significance of PAA-mediated regulation of QS.******My laboratory will use molecular biology tools and structural analysis to investigate whether PAA and other phenylalanine catabolism intermediates bind to quorum sensing regulators, and whether the identified interactions change their regulatory effect on virulence genes. B. cenocepacia, one of the species of the Bcc, can grow in the microoxic, amino acid-rich mucus of the CF lung and establish a chronic infection. To address the biological significance of PAA-related downregulation of virulence, we will investigate the contribution of phenylalanine degradation to QS-mediated pathogenicity in low oxygen conditions, where PAA degradation in Bcc may be abolished. B. cenocepacia is able to cause infection in the plant model Arabidopsis thaliana, allowing exploration of phenylalanine and PAA metabolism during a plant-bacteria interaction. PAA is a phytohormone and may be downregulated in plants as part of their defense mechanisms. To explore if B. cenocepacia can produce PAA-like molecules that enhance plant susceptibility to infection, we will use the A. thaliana host model and monitor disease progression in plants infected with B. cenocepacia mutants blocked at various stages of the PAA catabolism.******This research will establish the molecular basis of QS regulation by PAA catabolism, elucidating a novel link between two conserved bacterial features. The diverse pathogenic interactions of Bcc allow the use of plant and animal models. Thus, our findings will have broad implications for microbial metabolism during animal, human and plant-related microbial interactions. The cross-feeding between functional genomics, chemistry, and molecular biology will provide several training opportunities for interdisciplinary research, which is in high demand in the industry and academic sectors. Identification of the molecular mechanisms that connect the use of nutrients with QS will expose the intervening components as possible targets for therapeutic or biotechnological interventions. ***********