Interruption of the denitrification pathway influences cell growth and magnetosome formation in Magnetospirillum magneticum AMB-1

Lett Appl Microbiol. 2011 Jul;53(1):55-62. doi: 10.1111/j.1472-765X.2011.03063.x. Epub 2011 May 12.


Aims: Intracellular magnetosome synthesis in magnetotactic bacteria has been proposed to be a process involving functions of a variety of proteins. To learn more about the genetic control that is involved in magnetosome formation, nonmagnetic mutants are screened and characterized.

Methods and results: Conjugation-mediated transposon mutagenesis was applied to screen for nonmagnetic mutants of Magnetospirillum magneticum AMB-1 that were unable to respond to the magnetic field. A mutant strain with disruption of a gene locus encoding nitric oxide reductase was obtained. Growth and magnetosome formation under different conditions were further characterized.

Conclusions: Interruption of denitrification by inactivating nitric oxide reductase was responsible for the compromised growth and magnetosome formation in the mutant with shorter intracellular chains of magnetite crystals than those of wild-type cells under anaerobic conditions. Nevertheless, the mutant displayed apparently normal growth in aerobic culture.

Significance and impact of the study: Efficient denitrification in the absence of oxygen is not only necessary for maintaining cell growth but may also be required to derive sufficient energy to mediate the formation of magnetosome vesicles necessary for the initiation or activation of magnetite formation.

MeSH terms

  • Aerobiosis
  • Anaerobiosis
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Denitrification*
  • Ferrosoferric Oxide / metabolism
  • Magnetosomes / metabolism*
  • Magnetospirillum / cytology
  • Magnetospirillum / genetics
  • Magnetospirillum / growth & development*
  • Magnetospirillum / metabolism*
  • Mutagenesis
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism


  • Bacterial Proteins
  • Oxidoreductases
  • nitric-oxide reductase
  • Ferrosoferric Oxide