Iron Acquisition in Mycobacterium avium subsp. paratuberculosis.

Area of Science:

• Microbiology
• Genomics
• Bacterial Pathogenesis

Background:

• Mycobacterium avium subsp. paratuberculosis (MAP) is an animal pathogen requiring exogenous mycobactin for laboratory growth.
• MAP exhibits distinct iron uptake and mycobactin production compared to related M. avium subspecies.
• Gene deletions in the mycobactin biosynthesis pathway likely contribute to these unique phenotypes.

Purpose of the Study:

• To investigate the differences in mycobactin production and iron acquisition in MAP.
• To identify alternative iron uptake systems in MAP.
• To understand the role of horizontal gene transfer in MAP evolution.

Main Methods:

• Thin-layer chromatography and radiolabeled iron-uptake studies.
• Analysis of mycobactin synthesis genes and identification of mutations.
• Transposon-mediated mutagenesis screen to identify mycobactin-independent iron uptake systems.
• Genomic analysis of the LSP(P)15 island and gene expression studies.

Main Results:

• MAP demonstrates impaired mycobactin synthesis and iron acquisition.
• Multiple deletions were found in genes responsible for mycobactin synthesis.
• A horizontally acquired genomic island, LSP(P)15, was identified as a potential alternative iron uptake system.
• Mutants with disrupted LSP(P)15 genes showed increased iron uptake and intracellular iron content.

Conclusions:

• Horizontally acquired genes on LSP(P)15 contribute to iron acquisition in MAP.
• This alternative iron uptake system may have facilitated the loss of siderophore production in MAP.
• Horizontal gene transfer plays a significant role in the evolution of MAP.