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Infection and Immunity, January 2009, p. 307-316, Vol. 77, No. 1
0019-9567/09/$08.00+0     doi:10.1128/IAI.01194-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Function, Regulation, and Transcriptional Organization of the Hemin Utilization Locus of Bartonella quintana{triangledown} ,{dagger}

Nermi L. Parrow, Jasmin Abbott, Amanda R. Lockwood, James M. Battisti, and Michael F. Minnick*

Division of Biological Sciences, The University of Montana, Missoula, Montana 59812

Received 25 September 2008/ Returned for modification 21 October 2008/ Accepted 27 October 2008

Bartonella quintana is a gram-negative agent of trench fever, chronic bacteremia, endocarditis, and bacillary angiomatosis in humans. B. quintana has the highest known hemin requirement among bacteria, but the mechanisms of hemin acquisition are poorly defined. Genomic analyses revealed a potential locus dedicated to hemin utilization (hut) encoding a putative hemin receptor, HutA; a TonB-like energy transducer; an ABC transport system comprised of three proteins, HutB, HutC, and HmuV; and a hemin degradation/storage enzyme, HemS. Complementation analyses with Escherichia coli hemA show that HutA functions as a hemin receptor, and complementation analyses with E. coli hemA tonB indicate that HutA is TonB dependent. Quantitative reverse transcriptase PCR analyses show that hut locus transcription is subject to hemin-responsive regulation, which is mediated primarily by the iron response regulator (Irr). Irr functions as a transcriptional repressor of the hut locus at all hemin concentrations tested. Overexpression of the ferric uptake regulator (fur) represses transcription of tonB in the presence of excess hemin, whereas overexpression of the rhizobial iron regulator (rirA) has no effect on hut locus transcription. Reverse transcriptase PCR analyses show that hutA and tonB are divergently transcribed and that the remaining hut genes are expressed as a polycistronic mRNA. Examination of the promoter regions of hutA, tonB, and hemS reveals consensus sequence promoters that encompass an H-box element previously shown to interact with B. quintana Irr.

* Corresponding author. Mailing address: Division of Biological Sciences, The University of Montana, 32 Campus Drive, Missoula, MT 59812. Phone: (406) 243-5972. Fax: (406) 243-4184. E-mail: mike.minnick{at}mso.umt.edu

{triangledown} Published ahead of print on 3 November 2008.

{dagger} Supplemental material for this article may be found at http://iai.asm.org/.

Editor: A. Camilli

Infection and Immunity, January 2009, p. 307-316, Vol. 77, No. 1
0019-9567/09/$08.00+0     doi:10.1128/IAI.01194-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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