Magnetotaxis in Prokaryotes

Abstract

Magnetotaxis refers to the behaviour of some motile, aquatic, bacteria that orient and swim along magnetic field lines. These microorganisms, called magnetotactic bacteria (MTB), contain intracellular structures known as magnetosomes, which are nano‐sized, magnetic, iron‐mineral crystals, each enveloped by a biological (phospholipid bilayer) membrane. Magnetosomes are usually arranged in chains within the cell, providing it with a permanent magnetic dipole moment that facilitates location and retention in the cell's preferred habitat at or below the oxic–anoxic interface in the water column or sediment. Although all MTB are motile by means of flagella and have a cell wall structure characteristic of Gram‐negative bacteria, their diversity is reflected by the large number of different morphotypes found in environmental samples of water or sediment, and by phylogenetic analysis of both cultured and uncultured organisms. Key Concepts: Prokaryotes (bacteria), like eukaryotes, internally compartmentalise and contain organelles. The prokaryotic flagellum rotates clockwise and counter clockwise thereby propelling the cell during swimming. Magnetotaxis is bacterial motility directed by a magnetic field. Magnetotactic bacteria contain intracellular, nano‐scale, membrane‐enveloped, magnetic iron‐mineral crystals called magnetosomes. Magnetosomes impart a permanent magnetic dipole moment to cells of magnetotactic bacteria causing them to behave as miniature, motile, compass needles. Magnetotaxis works in conjunction with aerotaxis to increase energy transduction in magnetotactic bacteria. Genes for magnetosome formation are clustered in a region of the genomes of magnetotactic bacteria known as a magnetosome gene or genomic island. Magnetotactic bacteria are important in the cycling of a number of important elements including carbon, iron, nitrogen and sulfur.

Diversity and ecology of and biomineralization by magnetotactic bacteria

“…Magnetotactic bacteria (MTB) are motile prokaryotic organisms that biomineralize intracellular, single magnetic domain crystals of magnetite (Fe 3 O 4 ) and/or greigite (Fe 3 S 4 ) in lipid bilayer membranous vesicles called magnetosomes (Bazylinski et al ., ; Uebe and Schüler, ). Magnetosomes impart a permanent magnetic dipole moment to the cell causing it to align along magnetic field lines as it swims, a behaviour called magnetotaxis (Lefèvre et al ., ). Although MTB represent a diverse group in many ways, MTB are ubiquitous in most aquatic environments and global in distribution though appearing to be confined phylogenetically to the Domain Bacteria at this time (Lin et al ., ).…”

Looking for a needle in a haystack: magnetotactic bacteria help in “rare biosphere” investigations

“…that determine the magnetosome shape and size [9]. Bacterial cells use magnetosomes to align along magnetic field lines as they swim using their flagella in a behavior called magnetotaxis [10]. Magnetotaxis is believed to work with both chemotaxis and aerotaxis to assist MTB in maintaining an optimal position at the oxic-anoxic interface in chemically stratified water columns or sediments [11].…”