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Growing Magnetotactic Bacteria of the Genus Magnetospirillum: Strains MSR-1, AMB-1 and MS-1
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A magnetosome-associated cytochrome MamP is critical for magnetite crystal growth during the exponential growth phase

Azuma Taoka1, Yukako Eguchi, Shingo Mise

  • 1School of Natural System, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa, Japan; Bio-AFM Frontier Research Center, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa, Japan.

FEMS Microbiology Letters
|July 23, 2014
PubMed

Insights

Magnetotactic bacteria use MamP protein for iron biomineralization. This membrane-bound cytochrome is crucial for normal magnetite crystal growth during bacterial exponential growth.

Area of Science:

  • Microbiology
  • Biochemistry
  • Biomineralization

Background:

  • Magnetotactic bacteria synthesize intracellular magnetic crystals (magnetite or greigite) within organelles called magnetosomes.
  • These bacteria utilize a conserved set of proteins for this biomineralization process.
  • MamP, a novel cytochrome c with iron oxidase activity, is one such magnetosome-associated protein.

Purpose of the Study:

  • To investigate the function of the magnetotactic bacteria-specific protein MamP in magnetite biomineralization.
  • To determine the role of MamP in the growth and size regulation of magnetite crystals in Magnetospirillum magneticum AMB-1.

Main Methods:

  • Studied Magnetospirillum magneticum AMB-1, a model organism for magnetotactic bacteria.
  • Quantified MamP protein levels during different growth phases.
  • Overexpressed wild-type and mutated MamP (lacking heme c-binding motifs) in AMB-1 using plasmids.
  • Analyzed the number and size of magnetite crystals in genetically modified and wild-type cells.

Main Results:

  • MamP is a membrane-bound cytochrome whose expression increases during the exponential growth phase.
  • Overexpression of MamP in wild-type AMB-1 led to an increased number of magnetite crystals of normal size.
  • Mutating the heme c-binding motifs in MamP resulted in smaller magnetite crystals, despite normal crystal numbers.

Conclusions:

  • MamP plays a critical role in regulating the normal growth and size of magnetite crystals during the exponential growth phase in magnetotactic bacteria.
  • The iron oxidase activity of MamP is essential for proper magnetite biomineralization.
Keywords:
Magnetospirillum magneticum AMB-1bacterial organellebiomineralizationheme cironmagnetic particle

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