HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplementary data All Versions of this Article: mic.0.031948-0v1 155/11/3683    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Janagama, H. K. Articles by Sreevatsan, S. PubMed PubMed Citation Articles by Janagama, H. K. Articles by Sreevatsan, S. Agricola Articles by Janagama, H. K. Articles by Sreevatsan, S.

Identification and functional characterization of the iron-dependent regulator (IdeR) of Mycobacterium avium subsp. paratuberculosis

¹ Department of Veterinary Population Medicine, University of Minnesota, Saint Paul, MN, USA
² National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA, USA
³ PHRI, UMNDJ-New Jersey Medical School, Newark, NJ, USA
⁴ Foodborne Contaminants Research Unit, Agricultural Research Service, United States Department of Agriculture, Albany, CA, USA
⁵ Department of Veterinary Biomedical Sciences, University of Minnesota, Saint Paul, MN, USA

Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of Johne's disease in cattle and sheep, has unique iron requirements in that it is mycobactin-dependent for cultivation in vitro. The iron-dependent regulator (IdeR) is a well-characterized global regulator responsible for maintaining iron homeostasis in Mycobacterium tuberculosis (MTB). We identified an orthologous segment in the MAP genome, MAP2827, with >93 % amino acid identity to MTB IdeR. Electrophoretic mobility shift assays and DNase protection assays confirmed that MAP2827 binds the 19 bp consensus motif (iron box) on the MAP genome. Sequencing of MAP2827 from multiple isolates revealed a non-synonymous change (R91G) exclusive to sheep strains. Reporter gene assays and quantitative real-time RT-PCR assays in two diverse MAP strains and in an ideR deletion mutant of M. smegmatis (mc²155) suggested that both sheep MAP IdeR (sIdeR) and cattle MAP IdeR (cIdeR) repress mbtB transcription at high iron concentrations and relieve repression at low iron concentrations. On the other hand, bfrA (an iron storage gene) was upregulated by cIdeR when presented with MTB or the cattle MAP bfrA promoter, and was downregulated by sIdeR in the presence of MTB, or sheep or cattle MAP bfrA promoters, at high iron concentrations. The differential iron regulatory mechanisms between IdeR-regulated genes across strains may contribute to the differential growth or pathogenic characteristics of sheep and cattle MAP strains. Taken together, our study provides a possible reason for mycobactin dependency and suggests strong implications in the differential iron acquisition and storage mechanisms in MAP.

Correspondence
Srinand Sreevatsan
sreev001{at}umn.edu

A multiple sequence alignment of MAP2827c, MAP2827, MAV3604 and RV2711 and a table of PRODORIC-predicted putative MAP IdeR regulated genes are available with the online version of this paper.