Rodrigues Fiona, Sarkar-Tyson Mitali, Harding Sarah V, Sim Siew Hoon, Chua Hui Hoon, Lin Chi Ho, Han Xu, Karuturi R Krishna M, Sung Ken, Yu Kun, Chen Wei, Atkins Timothy P, Titball Richard W, Tan Patrick
Genome Institute of Singapore, 60 Biopolis Street, no. 02-01, Genome, Singapore 138672, Republic of Singapore.
J Bacteriol. 2006 Dec;188(23):8178-88. doi: 10.1128/JB.01006-06. Epub 2006 Sep 22.
Many microbial pathogens express specific virulence traits at distinct growth phases. To understand the molecular pathways linking bacterial growth to pathogenicity, we have characterized the growth transcriptome of Burkholderia pseudomallei, the causative agent of melioidosis. Using a fine-scale sampling approach, we found approximately 17% of all B. pseudomallei genes displaying regulated expression during growth in rich medium, occurring as broad waves of functionally coherent gene expression tightly associated with distinct growth phases and transition points. We observed regulation of virulence genes across all growth phases and identified serC as a potentially new virulence factor by virtue of its coexpression with other early-phase virulence genes. serC-disrupted B. pseudomallei strains were serine auxotrophs and in mouse infection assays exhibited a dramatic attenuation of virulence compared to wild-type B. pseudomallei. Immunization of mice with serC-disrupted B. pseudomallei also conferred protection against subsequent challenges with different wild-type B. pseudomallei strains. At a genomic level, early-phase genes were preferentially localized on chromosome 1, while stationary-phase genes were significantly biased towards chromosome 2. We detected a significant level of chromosomally clustered gene expression, allowing us to predict approximately 100 potential operons in the B. pseudomallei genome. We computationally and experimentally validated these operons by showing that genes in these regions are preferentially transcribed in the same 5'-->3' direction, possess significantly shorter intergenic lengths than the overall genome, and are expressed as a common mRNA transcript. The availability of this transcriptome map provides an important resource for understanding the transcriptional architecture of B. pseudomallei.
许多微生物病原体在不同的生长阶段表达特定的毒力特征。为了了解将细菌生长与致病性联系起来的分子途径，我们对类鼻疽病的病原体——伯克霍尔德菌的生长转录组进行了表征。通过精细采样方法，我们发现伯克霍尔德菌所有基因中约17%在丰富培养基中生长期间表现出表达调控，呈现为与不同生长阶段和转变点紧密相关的功能相关基因表达的广泛波动。我们观察到毒力基因在所有生长阶段均受到调控，并通过与其他早期毒力基因的共表达鉴定出serC为潜在的新毒力因子。serC基因缺失的伯克霍尔德菌菌株为丝氨酸营养缺陷型，在小鼠感染试验中与野生型伯克霍尔德菌相比毒力显著减弱。用serC基因缺失的伯克霍尔德菌免疫小鼠也能使其免受不同野生型伯克霍尔德菌菌株随后的攻击。在基因组水平上，早期基因优先定位在1号染色体上，而稳定期基因则明显偏向于2号染色体。我们检测到显著水平的染色体簇状基因表达，这使我们能够预测伯克霍尔德菌基因组中约100个潜在操纵子。我们通过计算和实验验证了这些操纵子，结果表明这些区域的基因优先沿相同的5'→3'方向转录，基因间长度明显短于整个基因组，并且作为共同的mRNA转录本表达。这一转录组图谱的可得为理解伯克霍尔德菌的转录结构提供了重要资源。
