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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.