Organisms and Environment Division, Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, UK.
ISME J. 2013 Aug;7(8):1568-81. doi: 10.1038/ismej.2013.36. Epub 2013 Mar 14.
Burkholderia cenocepacia is a Gram-negative aerobic bacterium that belongs to a group of opportunistic pathogens displaying diverse environmental and pathogenic lifestyles. B. cenocepacia is known for its ability to cause lung infections in people with cystic fibrosis and it possesses a large 8 Mb multireplicon genome encoding a wide array of pathogenicity and fitness genes. Transcriptomic profiling across nine growth conditions was performed to identify the global gene expression changes made when B. cenocepacia changes niches from an environmental lifestyle to infection. In comparison to exponential growth, the results demonstrated that B. cenocepacia changes expression of over one-quarter of its genome during conditions of growth arrest, stationary phase and surprisingly, under reduced oxygen concentrations (6% instead of 20.9% normal atmospheric conditions). Multiple virulence factors are upregulated during these growth arrest conditions. A unique discovery from the comparative expression analysis was the identification of a distinct, co-regulated 50-gene cluster that was significantly upregulated during growth under low oxygen conditions. This gene cluster was designated the low-oxygen-activated (lxa) locus and encodes six universal stress proteins and proteins predicted to be involved in metabolism, transport, electron transfer and regulation. Deletion of the lxa locus resulted in B. cenocepacia mutants with aerobic growth deficiencies in minimal medium and compromised viability after prolonged incubation in the absence of oxygen. In summary, transcriptomic profiling of B. cenocepacia revealed an unexpected ability of aerobic Burkholderia to persist in the absence of oxygen and identified the novel lxa locus as key determinant of this important ecophysiological trait.
洋葱伯克霍尔德氏菌是一种革兰氏阴性需氧细菌，属于一组具有不同环境和致病生活方式的机会性病原体。洋葱伯克霍尔德氏菌以其在囊性纤维化患者中引起肺部感染的能力而闻名，它拥有一个 8 Mb 的大型多复制子基因组，编码广泛的致病性和适应性基因。对 9 种生长条件下的转录组谱进行了分析，以确定当洋葱伯克霍尔德氏菌从环境生活方式转变为感染时，其全基因组基因表达的变化。与指数生长相比，结果表明，当生长停滞、静止期和令人惊讶的低氧浓度（6%而不是 20.9%正常大气条件）时，洋葱伯克霍尔德氏菌改变了其基因组的四分之一以上的表达。在这些生长停滞条件下，多种毒力因子上调。比较表达分析的一个独特发现是，鉴定出一个独特的、共同调节的 50 个基因簇，在低氧条件下生长时显著上调。这个基因簇被指定为低氧激活（lxa）基因座，编码六个普遍应激蛋白和预测参与代谢、运输、电子转移和调节的蛋白质。lxa 基因座的缺失导致洋葱伯克霍尔德氏菌突变体在最小培养基中有氧生长缺陷，并在长时间缺氧培养后存活能力下降。总之，洋葱伯克霍尔德氏菌的转录组谱分析揭示了需氧伯克霍尔德氏菌在没有氧气的情况下持续存在的意外能力，并确定了新的 lxa 基因座是这种重要生态生理特征的关键决定因素。
