The interplay between iron, haem and manganese in Porphyromonas gingivalis

BackgroundTransition metals including iron and manganese are necessary for life because of their ability to donate and accept electrons. Approximately one-third of all proteins require essential transition metal ions to perform catalytic, structural and regulatory functions. These essential metal ions react differently to the presence of oxygen radicals with iron directly involved in the formation of toxic reactive oxygen species, whilst manganese can protect against oxidative stress.HighlightAnaerobic bacterial species have been poorly studied with regard to transition metal homoeostasis and behave differently in many respects when compared with aerobic or aerotolerant species. To optimise catabolism whilst protecting themselves from unwanted reactions bacterial cells must maintain intracellular metal levels in a very narrow range that varies, dependent on the environment. To maintain metal ion homoeostasis, bacteria have evolved complex regulatory mechanisms of metal uptake, secretion and storage. In this review we examine how iron, haem and manganese availability dictate the lifestyle and virulence of the anaerobic Gram-negative, periodontal pathogen Porphyromonas gingivalis.ConclusionP. gingivalis has novel haem, iron and manganese transporters and metalloregulatory proteins that enable it to switch rapidly between an energy efficient iron-dependent virulent phase and a protective manganese-dependent survival phase.