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Title: Transcriptional Response of Leptospira interrogans to Different Iron Sources

Author
item LO, MIRANDA - MONASH UNIV.
item ELLIS, KATHERINE - MONASH UNIV.
item MURRAY, GERALD - MONASH UNIV.
item HAAKE, DAVID - UCLA
item MATSUNAGA, JAMES - UCLA
item Zuerner, Richard
item ADLER, BEN - MONASH UNIV.

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/8/2008
Publication Date: 4/8/2008
Citation: Lo, M., Ellis, K., Murray, G., Haake, D., Matsunaga, J., Zuerner, R.L., Adler, B. 2008. Transcriptional Response of Leptospira interrogans to Different Iron Sources [abstract]. GENOMES 2008: Functional Genomics of Microorganisms. Poster No. L16.

Interpretive Summary:

Technical Abstract: Australian Bacterial Pathogenesis Program, Department of Microbiology, Monash University, Victoria 3800, Australia (1), Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Department of Microbiology, Monash University, Victoria 3800, Australia (2), David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA (3), Division of Infectious Diseases, Veteran Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073, USA (4), Bacterial Diseases of Livestock Research Unit, National Animal Disease Center, USDA Agricultural Research Service, Ames, Iowa 50010, USA (5), Victorian Bioinformatics Consortium, Monash University, Victoria 3800, Australia (6). Leptospirosis is a globally important zoonotic disease. Humans can become infected via exposure to infected animals or contaminated water or soil. Iron is an essential element for many cellular processes and its sequestration in the host environment constitutes an immune defence mechanism. Pathogens have evolved complex iron acquisition and response mechanisms to control iron uptake and storage and to regulate expression of virulence factors upon entering the host. Heme is the most abundant form of iron in the host and is likely to be an important source of iron for L. interrogans during infection. Leptospires can utilise heme as a sole iron source and virulent strains demonstrate chemotaxis towards hemoglobin (Hb). However, relatively little is known about iron regulation and components of iron transport and metabolism in pathogenic Leptospira spp. Previous work in our laboratory showed that growth of L. interrogans varied under the different iron conditions tested; growth was most rapid when hemoglobin was the sole iron source, but not when hemoglobin and ferrous iron were present in the medium together. Therefore, this study used whole genome microarrays to investigate differences in gene expression during growth in EMJH medium with ferrous iron only, Hb only, or with both ferrous iron and Hb. During growth in EMJH with Hb only compared with ferrous iron only, a total of 44 genes was found to be differentially expressed. In Hb only compared with ferrous iron and Hb, 32 genes were differentially expressed, while in ferrous iron and Hb compared with ferrous iron only, 102 genes were differentially expressed. The gene encoding a putative heme oxygenase was up-regulated in the presence of Hb, with expression increasing when Hb was the sole iron source. Genes encoding heme biosynthetic pathway proteins were down-regulated in the presence of Hb, and their levels of expression decreased when Hb was the sole iron source. Expression of a number of other genes, including those involved in motility and chemotaxis and TonB dependent receptors, was found to vary depending on the iron source(s) present, suggesting the presence of distinct regulatory and signalling pathways in response to ferrous iron and Hb.