Differential Expression of Iron Acquisition Genes by Brucella melitensis and Brucella canis During Macrophage Infection (part 2). Brucella canis

Brucella melitensis and Brucella canis differ by ~75 genes yet B. melitensis is highly virulent for humans while B. canis is considered rarely pathogenic. No identified bacterial factors or mechanisms account for this difference in virulence. To identify functional differences of these two bacteria, gene transcription was examined during infection of murine macrophages and compared to bacteria grown in broth. Our analysis identified transcriptional differences in macrophage infection between B. melitensis and B. canis genes involved in iron transport. Increased transcription of the TonB, enterobactin, and ferric anguibactin transport systems were observed in B. canis but not B. melitensis during infection of macrophages. Therefore, iron appears as an important requirement during the first 24h of infection by B. canis but not for B. melitensis and provides strategies for controlling these pathogens. Overall design: Comparison of total bacterial RNA from Brucella canis infected murine macrophages at 5 and 24h

马尔他布鲁氏菌（Brucella melitensis）与犬布鲁氏菌（Brucella canis）之间存在约75个基因的序列差异，但马尔他布鲁氏菌对人类具有高度致病性，而犬布鲁氏菌通常被认为极少引发人类疾病。目前尚无明确的细菌致病因子或机制可阐释二者间的这种毒力差异。为揭示这两种布鲁氏菌的功能差异，本研究检测了它们感染小鼠巨噬细胞（murine macrophages）过程中的基因转录情况，并与液体肉汤培养基中培养的对应细菌进行了对照比较。分析结果显示，在巨噬细胞感染模型中，马尔他布鲁氏菌与犬布鲁氏菌的铁转运相关基因存在显著转录差异：感染巨噬细胞时，犬布鲁氏菌的TonB转运系统、肠杆菌素（enterobactin）以及铁性鳗菌素（ferric anguibactin）转运系统的转录水平均显著上调，而马尔他布鲁氏菌未出现此类转录变化。由此可见，铁是犬布鲁氏菌感染初期24小时内的关键必需营养因子，而马尔他布鲁氏菌则无此需求，该研究结果为这两种病原菌的防控提供了可行策略。总体设计：对感染犬布鲁氏菌的小鼠巨噬细胞在感染后5小时与24小时时提取的总细菌RNA进行比较分析。