Mechanisms of iron and haem transport by Listeria monocytogenes

Abstract

Listeria monocytogenes, the causative agent of listeriosis, is a virulent foodborne Gram-positive bacterial pathogen, with 20–30% mortality. It has a broad ability to transport iron, either in the form of ferric siderophores, or by extracting it from mammalian iron binding proteins. In this review we focus on the mechanisms of ferric siderophore and haem transport into the listerial cell. Despite the fact that it does not synthesize siderophores, L. monocytogenes transports ferric siderophores in the wild environment by the actions of cytoplasmic membrane ABC-transporter systems. The bacterium acquires haem, on the other hand, by two mechanisms. At low (nanomolar) concentrations, sortase B-dependent, peptidoglycan-anchored proteins scavenge the iron porphyrin in human or animal tissues, and transfer it to the underlying ABC-transporters in the cytoplasmic membrane for uptake. At concentrations at or above 50 nM, however, haem transport becomes sortase-independent, and occurs by direct interactions of the iron porphyrin with the same ABC-transporter complexes. The architecture of the Gram-positive cell envelope plays a fundamental role in these mechanisms, and the haem acquisition abilities of L. monocytogenes are an element of its ability to cause infectious disease.

Keywords::

• ABC transporter
• bacterial membrane
• iron transport
• mechanism
• membrane structure

Acknowledgements

The research was supported by National Institutes of Health (NIH) grant GM53836 and National Science Foundation (NSF) grant MCB0417694 to PEK and SMN, and funds from Trellis Biosciences, S. San Francisco, CA, USA. The funders had no role in experimental design, data collection and analysis, decision to publish, or preparation of the manuscript.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.