Magnetotactic Bacteria - Introduction

Introduction

The first description of magnetotactic bacteria appeared in 1963 in a publication of the Microbiology Institute (Italian: Instituto di Microbiologia) of the University of Pavia written by Salvatore Bellini. While observing bog sediments under his microscope, he noticed a group of bacteria that evidently oriented themselves in a unique direction. He realised these microorganisms moved according to the direction of the North Pole, and hence called them "magnetosensitive bacteria".

The first peer-reviewed article on magnetotactic bacteria appeared in a 1975 article in Science by Blakemore, a microbiologist at the Woods Hole Oceanographic Institution, who had similarly observed bacteria capable of orienting themselves in a certain direction: Blakemore realised that these microorganisms were following the direction of Earth's magnetic field, from south to north, and thus coined the term "magnetotactic".

These bacteria have been the subject of many experiments: They have even been aboard the Space Shuttle to examine their magnetotactic properties in the absence of gravity, but a definitive conclusion was not reached.

The sensitivity of magnetotactic bacteria to the Earth's magnetic field arises from the fact these bacteria precipitate chains of crystals of magnetic minerals within their cells; to date, all magnetotactic bacteria are reported to precipitate either magnetite or greigite. These crystals, and sometimes the chains of crystals, can be preserved in the geological record as magnetofossils. The oldest unambiguous magnetofossils come from the Cretaceous chalk beds of southern England, though less certain reports of magnetofossils extend to 1.9 billion years old Gunflint Chert. There have also been claims of their existence on Mars based on the shape of magnetite particles within the Martian meteorite ALH84001, but these claims are highly contested.