Investigating Iron Transport and Utilization Features of Acinetobacter baumannii

<i>Acinetobacter baumannii</i> is an important opportunistic human pathogen that causes severe nosocomial infections. The bacterium must overcome iron starvation and oxidative stress conditions imposed by the host in order to propagate and cause disease. This work further investigates the transport and utilization of iron by <i>A. baumannii</i>, and their involvement in virulence. The transport of iron is an active process and requires energy; <i>A. baumannii</i> ATCC 19606^T contains and expresses three gene loci encoding functions in the TonB energy-transducing complex to provide the energy needed for iron transport. Transformation of <i>Escherichia coli</i> KP1344 with plasmids harboring the TonB components of these <i>A. baumannii</i> TonB systems promoted cell growth under iron-chelated conditions, which shows that these systems provide the necessary energy needed for iron acquisition. Inactivation of <i>tonB</i>₁ and <i>tonB</i>₂ in <i>A. baumannii</i> resulted in growth restriction under iron-chelation, indicating these genes are involved in iron transport. The <i>Galleria mellonella</i> infection model showed that TonB₁ and TonB₂ are involved, but are not essential for bacterial virulence, indicating <i>A. baumannii</i> carries redundant functional TonBs. Furthermore, TonB₂ plays an additional role in the interaction with A549 human alveolar cells. Inactivation of <i>dppA₁A₂</i> and <i>dppBC</i>, components of an inner membrane ABC transporter, did not affect growth under iron-chelation, suggesting alternative transport functions. However, inactivation of <i>cirA</i>, which codes for an iron-regulated outer membrane receptor resulted in reduced growth under iron-chelated conditions, indicating CirA has a role in iron transport. Furthermore, <i>A. baumannii</i> expresses hemin utilization functions independent of production and transport of acinetobactin-siderophore. Following transport, iron must be integrated into the intracellular iron pool. NfuA, a [Fe-S] cluster carrier protein was found to be involved in the ability of cells to respond to iron-limitation and oxidative stress, and is also needed for successful virulence in <i>G. mellonella</i> and within A549 cells. NfuA could be used for the maturation of intracellular [Fe-S] cluster containing proteins needed for the response to stresses encountered in the host. Taken together, the results here demonstrate that <i>A. baumannii</i> has implemented multiple mechanisms for the uptake and utilization of iron to ensure survival and propagation within the human host.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Microbiology

Grantor dc:publisher

Miami University

Year dc:date

2013

Author dc:creator

• Zimbler, Daniel Lawrence

Contributors dc:contributor

• Actis, Luis

• Microbiology
• Acinetobacter baumannii
• Iron Acquisition
• Iron-Sulfur Cluster
• Iron Regulation

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=miami1364395692

OAI identifier oai:identifier

oai:etd.ohiolink.edu:miami1364395692