Review
The interplay between iron, haem and manganese in Porphyromonas gingivalis

https://doi.org/10.1016/j.job.2014.12.003Get rights and content

Abstract

Background

Transition 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.

Highlight

Anaerobic 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.

Conclusion

P. 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.

Introduction

Chronic periodontitis is the most common of the destructive periodontal diseases amongst adults and its prevalence and severity increase with age. The global age-standardised prevalence of severe periodontitis between 1990 and 2010 was 11%, however the exact percentage varies between and within countries [1], [2], [3]. In the USA, 38% of the adult population 30 years and older and 65% of adults 65 years and older have either severe or moderate periodontitis [4], [5]. Epidemiological surveys have shown that clinical indicators of chronic periodontal disease are associated with a greater risk of certain cancers such as squamous cell carcinoma of the head, neck, and oesophagus [6], cancer of the tongue [7] and pancreatic cancer [8], [9], [10]. There is also a relationship between chronic periodontitis and systemic diseases and disorders such as cardiovascular disease [11], preterm and underweight birth [12], systemic inflammation in solid-organ transplant recipients [13], diabetes and rheumatoid arthritis [11], [14], [15], [16].

The bacterial aetiology of chronic periodontitis is acknowledged to be polymicrobial in nature. Whilst the concepts of the roles of particular oral bacterial species in disease have changed over the past two decades, there is consensus that the anaerobic, proteolytic, amino acid fermenting species Porphyromonas gingivalis plays a significant role in either initiation or progression of disease [17], [18], [19], [20]. Based on animal model data P. gingivalis has recently been proposed to be a “keystone pathogen” that manipulates the host response to favour the proliferation of a pathogenic polymicrobial biofilm (dysbiosis) and development of disease [19]. We have previously demonstrated in a longitudinal human study that the imminent progression of chronic periodontitis could be predicted by increases in the relative levels of P. gingivalis and/or Treponema denticola in subgingival plaque [21], which is consistent with other clinical studies demonstrating that P. gingivalis levels in subgingival plaque are predictive of human disease progression [22], [23], [24]. P. gingivalis is also capable of causing periodontitis in animal models of disease [25], [26].

Section snippets

Divalent metal cations

All living cells acquire transition metal ions to meet their basic cellular needs, with iron, manganese, copper, zinc, nickel and cobalt being of greatest physiological relevance [27], [28]. It has been estimated that about one-third of all proteins require essential transition metal ions to perform catalytic, structural and regulatory functions [29], [30]. Metals such as iron, copper, chromium, manganese and cobalt are capable of redox cycling in which a single electron may be accepted or

Oxidative stress

Stepwise reduction of molecular oxygen (O2) by high-energy exposure or electron-transfer reactions leads to production of highly reactive oxygen species (ROS). The conversion of atmospheric oxygen to ROS occurs inside actively respiring aerobic or facultative bacterial cells [48]. However, few ROS are generated intracellularly by anaerobic bacteria due to the absence of molecular oxygen in their environment. Commensal and pathogenic bacteria can also be exposed to the oxidative burst of

P. gingivalis

P. gingivalis is a Gram-negative, sessile, obligate anaerobe that has an absolute requirement for iron and its growth and virulence are dependent on the availability of iron complexes such as haem [54], [55], [56], [57] or ferrous iron [58]. In addition P. gingivalis cannot synthesise protoporphyrin IX [59], a porphyrin derivative that combines with ferrous iron to form haem, a cofactor for several enzymes, which can be bound transiently [60], or remain bound to the protein permanently [61].

P.

Metal acquisition systems of P. gingivalis

P. gingivalis like most anaerobic bacteria does not produce siderophores to scavenge environmental iron or compete with transferrin or lactoferrin for ferric iron binding [70]. P. gingivalis utilises human transferrin as a source of iron and peptides via proteolytic cleavage by the cell surface Arg- and Lys-specific cysteine proteinases, RgpA/B and Kgp, collectively known as gingipains [71], [72]. In the absence of gingipains P. gingivalis cannot remove the iron from transferrin [71]. The

The polymicrobial biofilm nature of health and disease

P. gingivalis is a normal component of the human oral microbiota and is a late coloniser of polymicrobial oral biofilms, relying on complex interactions with a range of other oral bacteria including Streptococcus gordonii, Fusobacterium nucleatum, Tannerella forsythia and T. denticola [112], [113], [114]. Therefore although much has been learnt by studying P. gingivalis in isolation, its interactions with other bacterial species in the biofilm will have a considerable influence on its role as

Metalloregulatory proteins

To protect against the toxic effect of the Fenton reaction, cells must utilise, store and maintain iron concentrations with careful management of cellular free iron sequestered in high affinity protein-bound forms [125]. Intracellular concentrations of metal ions in living cells are maintained and co-ordinated through a system known as metal ion homoeostasis that involves metal ion influx across the cell membrane depending on the intracellular metal ion concentration, availability and demand.

Walking the tightrope: the nexus between haem, iron, manganese and oxygen

There is interplay between iron and manganese homoeostasis in P. gingivalis as in a FeoB mutant, which had half the cellular iron of wild-type, there was a concomitant three-fold increase in cellular manganese [58]. This increase in cellular manganese content in the P. gingivalis mutant was attributed to manganous ions binding to vacant sites of ferrous ion binding proteins thus lowering the free manganous ion concentration within the cell. Given the link between increased OxyR expression under

Conclusion

The clear interplay between iron, manganese, haem and oxidative stress protection may enable the anaerobic P. gingivalis to maintain a high level of intracellular ferrous iron to maximise growth and virulence using energy efficient iron-dependent metabolism, but to rapidly replace this potentially deadly metal with manganese for survival during oxidative stress by switching to a more protective, but much more restrictive, manganese-based physiology.

Ethical approval

Ethical approval was not required.

Conflict of interest

There are no potential conflicts of interest to be disclosed.

References (165)

  • J. Cadet et al.

    Oxidative damage to DNA: formation, measurement and biochemical features

    Mutat Res – Fundam Mol Mech Mutagen

    (2003)
  • M. Freitas et al.

    Optical probes for detection and quantification of neutrophils׳ oxidative burst. A review

    Anal Chim Acta

    (2009)
  • S. Stohs et al.

    Oxidative mechanisms in the toxicity of metal ions

    Free Radic Biol Med

    (1995)
  • T. Olczak et al.

    Iron and heme utilization in Porphyromonas gingivalis

    FEMS Microbiol Rev

    (2005)
  • S.G. Dashper et al.

    A novel Porphyromonas gingivalis FeoB plays a role in manganese accumulation

    J Biol Chem

    (2005)
  • J.M. Roper et al.

    The enigma of cobalamin (Vitamin B12) biosynthesis in Porphyromonas gingivalis: identification and characterization of a functional corrin pathway

    J Biol Chem

    (2000)
  • A. de Lillo et al.

    Binding and degradation of lactoferrin by Porphyromonas gingivalis, Prevotella intermedia and Prevotella nigrescens

    FEMS Immunol Med Microbiol

    (1996)
  • J.D. Oram et al.

    Inhibition of bacteria by lactoferrin and other iron-chelating agents

    BBA Gen Subj

    (1968)
  • W. Bellamy et al.

    Identification of the bactericidal domain of lactoferrin

    BBA Protein Struct Mol Enzymol

    (1992)
  • Y. Shi et al.

    Genetic analyses of proteolysis, hemoglobin binding, and hemagglutination of Porphyromonas gingivalis: construction of mutants with a combination of rgpA, rgpB, kgp and hagA

    J Biol Chem

    (1999)
  • S. Shizukuishi et al.

    Effect of concentration of compounds containing iron on the growth of Porphyromonas gingivalis

    FEMS Microbiol Lett

    (1995)
  • K.D. Krewulak et al.

    Structural biology of bacterial iron uptake

    BBA Biomebr

    (2008)
  • T. Olczak et al.

    Purification and initial characterization of a novel Porphyromonas gingivalis HmuY protein expressed in Escherichia coli and insect cells

    Protein Expr Purif

    (2006)
  • J.-L. Gao et al.

    Characterization of a hemophore-like protein from Porphyromonas gingivalis

    J Biol Chem

    (2010)
  • T.E. Bramanti et al.

    Effect of porphyrins and host iron transport proteins on outer membrane protein expression in Porphyromonas (Bacteroides) gingivalis: identification of a novel 26 kDa hemin-repressible surface protein

    Microb Pathog

    (1992)
  • N.J. Kassebaum et al.

    Global burden of severe periodontitis in 1990–2010: a systematic review and meta-regression

    J Dent Res

    (2014)
  • B.A. Dye

    Global periodontal disease epidemiology

    Periodontology 2000

    (2012)
  • P.E. Petersen et al.

    Periodontal health and global public health

    Periodontology 2000

    (2012)
  • P.I. Eke et al.

    Prevalence of periodontitis in adults in the United States: 2009 and 2010

    J Dent Res

    (2012)
  • P.N. Papapanou

    The prevalence of periodontitis in the US: forget what you were told

    J Dent Res

    (2012)
  • N. Guha et al.

    Oral health and risk of squamous cell carcinoma of the head and neck and esophagus: results of two multicentric case-control studies

    Am J Epidemiol

    (2007)
  • M. Tezal et al.

    Chronic periodontitis and the risk of tongue cancer

    Arch Otolaryngol Head Neck Surg

    (2007)
  • D.S. Michaud et al.

    A prospective study of periodontal disease and pancreatic cancer in US male health professionals

    J Natl Cancer Inst

    (2007)
  • R.J. Genco et al.

    Prevention: reducing the risk of CVD in patients with periodontitis

    Nat Rev Cardiol

    (2010)
  • A. Spahr et al.

    Periodontal infection and coronary heart disease

    Arch Intern Med

    (2006)
  • E. Ioannidou et al.

    Elevated serum interleukin-6 (IL-6) in solid-organ transplant recipients is positively associated with tissue destruction and IL-6 gene expression in the periodontium

    J Periodontol

    (2006)
  • K. Lundberg et al.

    Periodontitis in RA-the citrullinated enolase connection

    Nat Rev Rheumatol

    (2010)
  • E. Lalla et al.

    Diabetes mellitus and periodontitis: a tale of two common interrelated diseases

    Nat Rev Endocrinol

    (2011)
  • N. Gully et al.

    Porphyromonas gingivalis peptidylarginine deiminase, a key contributor in the pathogenesis of experimental periodontal disease and experimental arthritis

    PLoS One

    (2014)
  • S.S. Socransky et al.

    Microbial complexes in subgingival plaque

    J Clin Periodontol

    (1998)
  • R. Darveau

    Periodontitis: a polymicrobial disruption of host homeostasis

    Nat Rev Microbiol

    (2010)
  • G. Hajishengallis et al.

    The keystone-pathogen hypothesis

    Nat Rev Microbiol

    (2012)
  • S.J. Byrne et al.

    Progression of chronic periodontitis can be predicted by the levels of Porphyromonas gingivalis and Treponema denticola in subgingival plaque

    Oral Microbiol Immunol

    (2009)
  • L.F. Brown et al.

    Incidence of attachment loss in community-dwelling older adults

    J Periodontol

    (1994)
  • A.D. Haffajee et al.

    Relation of baseline microbial parameters to future periodontal attachment loss

    J Clin Periodontol

    (1991)
  • A.L. Griffen et al.

    Prevalence of Porphyromonas gingivalis and periodontal health status

    J Clin Microbiol

    (1998)
  • R.H. Orth et al.

    Synergistic virulence of Porphyromonas gingivalis and Treponema denticola in a murine periodontitis model

    Mol Oral Microbiol

    (2011)
  • R.D. Pathirana et al.

    Kgp and RgpB, but not RgpA, are important for Porphyromonas gingivalis virulence in the murine periodontitis model

    Infect Immun

    (2007)
  • Z. Ma et al.

    Coordination chemistry of bacterial metal transport and sensing

    Chem Rev

    (2009)
  • A. Van Ho et al.

    Transition metal transport in yeast

    Annu Rev Microbiol

    (2002)
  • Cited by (4)

    • Oral biosciences: The annual review 2015

      2016, Journal of Oral Biosciences
    • Lysine acetylation is a common post-translational modification of key metabolic pathway enzymes of the anaerobe Porphyromonas gingivalis

      2015, Journal of Proteomics
      Citation Excerpt :

      Other pathways, such as glycan biosynthesis [50] and metabolism, and the metabolism of terpenoids and polyketides had no detected acetylated proteins, suggesting that under the tested growth condition particular metabolic pathways had been targeted for lysine acetylation. Metabolic pathways of P. gingivalis are tightly regulated at the transcriptional level [51–53] and are likely to be highly regulated at the post-translational level as inferred by the majority of the lysine-acetylated P. gingivalis proteins we detected being metabolic enzymes. P. gingivalis relies on the complex anaerobic fermentation of amino acids, particularly aspartate and glutamate to produce energy (Fig. 3) [1].

    View full text