School of Biological Sciences, Flinders University, Adelaide, SA 5001, Australia.
BMC Genomics. 2011 Feb 23;12:126. doi: 10.1186/1471-2164-12-126.
Iron acquisition systems are important virulence factors in pathogenic bacteria. To identify these systems in Acinetobacter baumannii, the transcriptomic response of the completely sequenced strain ATCC 17978 under iron limiting conditions was investigated using a genomic microarray that contained probes for all annotated open reading frames.
Under low iron conditions, transcription levels were more than 2-fold up-regulated for 463 genes, including 95 genes that were up-regulated more than 4-fold. Of particular significance, three siderophore biosynthesis gene clusters, including one novel cluster, were highly up-regulated. Binding sites for the ferric uptake regulator were identified in the promoter regions of many up-regulated genes, suggesting a prominent role for this regulator in the Acinetobacter iron acquisition response. Down-regulation under iron limitation was less dramatic as the transcription of only 202 genes varied more than 2-fold. Various genes involved in motility featured prominently amongst the genes down-regulated when iron was less readily available. Motility assays confirmed that these transcriptional changes are manifested at the phenotypic level. The siderophore biosynthesis gene clusters were further investigated by means of comparative genomic analysis of 10 sequenced Acinetobacter isolates. These analyses revealed important roles for mobile genetic elements in shaping the siderophore meditated iron acquisition mechanisms between different Acinetobacter strains.
A. baumannii grown under iron limited conditions resulted in major transcriptional changes of not only many iron acquisition related genes, but also genes involved in other processes such as motility. Overall, this study showed that A. baumannii is well adaptable to growth in an environment which has limiting iron availability.
铁获取系统是病原菌中重要的毒力因子。为了鉴定鲍曼不动杆菌中的这些系统，我们使用基因组微阵列研究了完全测序的 ATCC 17978 菌株在缺铁条件下的转录组反应，该微阵列包含所有注释开放阅读框的探针。
在低铁条件下，463 个基因的转录水平上调了 2 倍以上，其中 95 个基因上调了 4 倍以上。特别重要的是，三个铁载体生物合成基因簇，包括一个新的簇，高度上调。在许多上调基因的启动子区域中鉴定到了铁摄取调节剂的结合位点，这表明该调节剂在鲍曼不动杆菌铁获取反应中起着重要作用。由于只有 202 个基因的转录变化超过 2 倍，因此在铁限制下的下调不那么明显。当铁不易获得时，许多与运动相关的基因在下调的基因中表现突出。运动性测定证实了这些转录变化在表型水平上的表现。通过对 10 株已测序的鲍曼不动杆菌分离株进行比较基因组分析，进一步研究了铁载体生物合成基因簇。这些分析表明，移动遗传元件在塑造不同鲍曼不动杆菌菌株之间的铁载体介导的铁获取机制方面发挥了重要作用。
在缺铁条件下生长的鲍曼不动杆菌不仅导致许多铁获取相关基因的主要转录变化，而且还导致与运动等其他过程相关的基因发生变化。总体而言，这项研究表明，鲍曼不动杆菌能够很好地适应铁有限环境中的生长。
