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THE EFFECT OF IRON AVAILABILITY ON MYCOBACTERIAL CELL METABOLISM - A GENOMIC AND PROTEOMIC APPROACH. Wilkins ML 1,2, Vaughan J1, Lanigan M1, Beddome G1, Shiell B1, Lea-Smith D3, Crellin P3, Coppel R3, Luke RKJ2, Tizard M1 and Michalski WP1 1 CSIRO Livestock Industries, Australian Animal Health Laboratories Geelong, Australia 2 Department of Agriculture, La Trobe University Bundoora, VIC Australia. 3 Department of Microbiology, Monash University Clayton, VIC Australia Many species within the family Mycobacteriaceae namely M. tuberculosis, M. bovis, M. leprae, M. avium ssp. avium (Maa) and M. avium ssp. paratuberculosis (Mptb) are known causative agents of human and animal diseases. Within the animal host free iron is limited and the availability of iron to infecting mycobacteria is thought to play a major role in the development of pathogenicity. Mycobacteria have developed effective iron acquisition systems that involve the production of siderophores: mycobactin, exochelin and carboxymycobactin. Iron is an essential element for most organisms, and functions as prosthetic groups in components of key metabolic pathways such as electron transport, oxidative metabolism and transmembrane transport. Conditions for iron-deficient cultures were optimised for the fast growing M. smegmatis (non pathogenic mycobacterium) and applied to the slow growing Maa. Confirmation of iron deficiency in cultures was determined using Reverse Transcription Quantitative Real Time PCR and an exochelin bioassay. Our laboratory is utilising both genomic and proteomic technologies to study the effect of iron deprivation on mycobacterial cell metabolism. A small microarray of genes from M. smegmatis is being used to study changes in gene expression profiles at the transcriptional level. Proteomic profiles of iron-deficient cultures have been generated using both one- and two-dimensional electrophoresis and compared with those grown under unmodified conditions. Differentially expressed proteins were analysed using mass spectrometry and N-terminal sequencing. The potential role of genes and proteins found to be regulated in response to iron deprivation will be discussed in relation to the pathogenicity of mycobacteria such as Mptb, the causative agent of Johne’s Disease.