Essential metal ions act as co-factors that enable enzymes to catalyse a wider range of chemical transformations than would be achievable using solely organic catalysts. The precise metal requirements of organisms vary between species, environmental niches, metabolic states and circadian rhythms.
Metals are required cofactors for numerous processes that are essential to both pathogen and host. They are coordinated in enzymes responsible for DNA replication and transcription, relief from oxidative stress, and cellular respiration. However, excess transition metals can be toxic due to their ability to cause spontaneous redox cycling and disrupt normal metabolic processes. Vertebrates have evolved intricate mechanisms to limit the availability of some crucial metals while concurrently flooding sites of infection with antimicrobial concentrations of other metals.
Both pathogens and hosts have complex regulatory systems for metal homeostasis. Understanding these provides strategies for fighting pathogens, either by excluding essential metals from the microbes, by delivery of excess metals to cause toxicity, or by complexing metals in microorganisms.