Identification of key factors for anoxic survival of B. cenocepacia H111

Burkholderia cenocepacia is an opportunistic pathogen that can lead to severe infections in patients suffering from cystic fibrosis (CF) and chronic granulomatous disease. Being an obligate aerobe, B. cenocepacia is unable to grow in the absence of oxygen. In this study, we show that the CF isolate B. cenocepacia H111 can survive in the absence of oxygen. Using a transposon sequencing (Tn-seq) approach we identified 71 fitness determinants involved in anoxic survival, including a Crp-Fnr family transcriptional regulatory gene (anr2), genes coding for the sensor kinase RoxS and its response regulator RoxR, the sigma factor for flagella biosynthesis (FliA) and subunits of a cytochrome bd oxidase (CydA, CydB and the potentially novel subunit CydP). Individual knockouts of these fitness determinants significantly reduced anoxic survival and inactivation of both anr copies is shown to be lethal under anoxic conditions. We also show that the two-component system RoxS/RoxR and FliA are important for virulence and swarming/swimming, respectively.

洋葱伯克霍尔德菌（Burkholderia cenocepacia）是一种机会致病菌，可引发囊性纤维化（CF）与慢性肉芽肿病患者出现严重感染。作为专性需氧菌，该菌无法在无氧环境中生长。本研究发现，囊性纤维化分离株洋葱伯克霍尔德菌H111可在无氧环境下存活。通过转座子测序（Tn-seq）技术，我们鉴定出71个参与无氧存活的适合度决定因子，包括Crp-Fnr家族转录调控基因anr2、编码感应激酶RoxS及其应答调节蛋白RoxR的基因、鞭毛生物合成相关σ因子（sigma factor）FliA，以及细胞色素bd氧化酶的亚基CydA、CydB与潜在新型亚基CydP。上述适合度决定因子的单基因敲除均会显著降低该菌的无氧存活能力，且两个anr拷贝的失活在无氧条件下被证实具有致死性。本研究同时证实，双组分系统（two-component system）RoxS/RoxR与σ因子FliA分别对毒力与群集运动、泳动运动至关重要。