Copper Homeostasis and Virulence in Listeria Monocytogenes

The project aims to understand copper homeostasis in Listeria monocytogenes and the role of copper homeostasis in infection. Copper is essential for many bacteria being an important prosthetic group for certain enzymes. However at high levels copper is toxic in part due to its ability to redox cycle and catalyse the formation of oxygen derived free radicals. As such bacteria need to be able to maintain copper homeostasis.
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In L. monocytogenes the problem of copper homeostasis is particularly acute. It inhabits a range of environments including soil, effluents and food where it will be exposed to fluctuating copper levels. The use of copper as an anti-microbial in animal feeds, as a disinfectant in factory-based farming and as a biocide in fruit production means L. monocytogenes will have to combat potentially toxic levels of copper during food production and processing.
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Adapting to fluctuations in the level of copper is important during infections. L. monocytogenes replicates in a number of host tissues that will offer different challenges with regard to copper availability. Early in infection L. monocytogenes grows in the gall bladder, where there are high levels of copper, as such it will have to adapt to high levels of copper. In contrast, in the liver and spleen it replicates in an environment in which there will be little free copper and where the acquisition of sufficient copper for growth will be essential. Adapting to these different niches within the host offers a challenge in terms of maintaining a supply of copper for copper requiring enzymes whilst avoiding copper toxicity.
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The proposal has five objectives.

<OL> <LI> To determine the role of the CopC/D protein in copper homeostasis.

<LI> To determine the mechanism of regulation of cueA and copC/D genes in response to copper.

<LI> To use micro-array analyses to show that a wider range of listerial genes are expressed during copper homeostasis and to identify these genes.

<LI> To test the hypothesis that adaptation to a low copper environment copper is essential for intracellular survival or replication in L. monocytogenes

<LI> To elucidate the role of copper homeostasis in the survival and growth of L. monocytogenes during infection in vivo: adaptation to both low and high copper levels in the liver, spleen and gall bladder.