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Type: Journal article
Title: Investigation of the human pathogen Acinetobacter baumannii under iron limiting conditions
Author: Eijkelkamp, B.
Hassan, K.
Paulsen, I.
Brown, M.
Citation: BMC Genomics, 2011; 12(1):126-1-126-14
Publisher: BioMed Central
Issue Date: 2011
ISSN: 1471-2164
Statement of
Bart A Eijkelkamp, Karl A Hassan, Ian T Paulsen, and Melissa H Brown
Abstract: BACKGROUND: 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. RESULTS: 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. CONCLUSIONS: 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.
Keywords: Acinetobacter baumannii; Iron; RNA, Bacterial; Siderophores; Oligonucleotide Array Sequence Analysis; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Binding Sites; Base Sequence; Genome, Bacterial; Multigene Family; Open Reading Frames; Promoter Regions, Genetic; Comparative Genomic Hybridization
Rights: © 2011 Eijkelkamp et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
RMID: 0030012722
DOI: 10.1186/1471-2164-12-126
Appears in Collections:Microbiology and Immunology publications

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