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Assmilation of iron by pathogenic Neisseria spp
Abstract:
Iron assimilation by Neisseria meningitidis and Neisseria gonorrhoeae has been shown to be important to their growth and virulence. Iron acquisition in vitro was studied in an agar diffusion assay employing the iron-binding protein conalbumin. The ability of various iron compounds to alter the growth-inhibitory effect of conalbumin was investigated. On an equimolar iron basis, citrate-containing iron compounds were most effective; hemin was slightly less effective; ferrous sulfate and ferrous ammonium sulfate were even less effective; and the ferric compounds, ferric nitrate, ferric chloride, and ferric dextran (Imferon), were least effective. The results suggested that, as with Escherichia coli and certain other bacteria, the Neisseria spp. may utilize a citrate-mediated iron transport system. Microbial siderophores were also tested for their ability to relieve the growth-inhibitory effect of conalbumin. Two phenolate siderophores and Desferal enhanced growth inhibition in the deferrated form, but were inactive in the ferrated form. Several trihydroxamates of the ferrichrome family and coprogen were inactive in either the deferrated or ferrated forms. Of the 12 different siderophores tested, only the dihydroxamates (schizokinen, arthrobactin, and aerobactin) were stimulatory, but then only in the ferrated forms. Apparently, even though those siderophores could be utilized as specific iron transport agents by the Neisseria spp., they could not compete with conalbumin for iron under these assay conditions.
Insights
Neisseria meningitidis and Neisseria gonorrhoeae utilize citrate for iron uptake, outcompeting some siderophores. Iron compounds
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Nutritional Biochemistry
Background:
- Iron assimilation is crucial for Neisseria meningitidis and Neisseria gonorrhoeae growth and virulence.
- Understanding iron acquisition mechanisms is vital for combating these bacterial pathogens.
Purpose of the Study:
- To investigate in vitro iron acquisition mechanisms utilized by Neisseria species.
- To assess the efficacy of various iron compounds and microbial siderophores in overcoming iron-binding proteins.
Main Methods:
- Agar diffusion assay using the iron-binding protein conalbumin.
- Testing the effect of different iron compounds (citrate, hemin, sulfates, ferric compounds) on bacterial growth.
- Evaluating the ability of various siderophores (phenolate, trihydroxamates, dihydroxamates) to relieve conalbumin-mediated growth inhibition.
Main Results:
- Citrate-containing iron compounds were most effective in promoting Neisseria growth against conalbumin.
- Hemin, ferrous sulfate, and ferrous ammonium sulfate showed moderate effectiveness.
- Ferric compounds (nitrate, chloride, dextran) were least effective; certain dihydroxamate siderophores were stimulatory only in ferrated forms but could not outcompete conalbumin.
Conclusions:
- Neisseria species likely employ a citrate-mediated iron transport system.
- While some siderophores can be utilized, they may not effectively compete with host iron-binding proteins like conalbumin under certain conditions.