: The bacterium BW-1 swimming toward magnetic field.
In the Dec. 23 issue of Science magazine, 51³Ô¹ÏºÚÁÏ microbiologist Dennis Bazylinski and an international team of researchers explain how they were the first to identify, isolate and grow a type of magnetic bacteria that could one day contribute to the emerging biotech and nanotechnology industries.
Magnetotactic bacteria are simple, single-celled organisms that are found in almost all bodies of water. As their name suggests, they orient and navigate along magnetic fields like miniature swimming compass needles. This is due to nano-sized crystals of the minerals magnetite or greigite that they produce.
The presence of these magnetic crystals makes the bacteria and their internal crystals (called magnetosomes) desirable for commercial applications like drug delivery and enhancement of medical imaging.
While many magnetite-producing bacteria can be grown and easily studied, Bazylinski and his team were the first to cultivate a greigite-producing species. The greigite-producing bacterium, called BW-1, was found in water samples collected more than 280 feet below sea level in Death Valley National Park's Badwater Basin.
"Because greigite-producing bacteria have never been isolated, the crystals haven't been tested for the types of biomedical and other applications that currently employ magnetite," said Bazylinski, who has been studying magnetotactic bacteria for more than 30 years. "Greigite, an iron sulfide, may be superior to the iron oxide magnetite in some applications due to its slightly different physical and magnetic properties, and we'll now have the opportunity to find out."
After the BW-1 was collected, it was isolated and grown at 51³Ô¹ÏºÚÁÏ by Bazylinski and then-postdoctoral associate Christopher Lef?vre. The bacterium was found to produce both greigite and magnetite.
A detailed examination of its DNA revealed that BW-1 has two sets of magnetosome genes, unlike others that produce only one mineral and have only one set of magnetosome genes. This suggests that the production of magnetite and greigite in BW-1 is likely controlled by separate sets of genes. This could be important in the mass production of either mineral for specific applications.
According to Bazylinski, the greigite-producing bacteria represent a new, previously unrecognized group of sulfate-reducing bacteria that breathe with the compound sulfate rather than oxygen as most living organisms do.
"It is surprising that given how much is known about the sulfate-reducing bacteria, that no one has described this group," Bazylinski said.
The study, "," was funded in part by a grant from the U.S. National Science Foundation, the U.S. Department of Energy and the French Foundation for Medical Research.
Partnering with Bazylinski were Christopher Lef?vre and David Pignol of the Institute of Biology and Biotechnology, French National Center of Scientific Research and University of Aix-Marseille II (France); Nicolas Menguy of Pierre and Marie Curie University (France); Fernanda Abreu and Ulysses Lins of the Federal University of Rio de Janeiro (Brazil); Mihaly Posfai of the University of Pannonia (Hungary); Tanya Prozorov of Ames Laboratory; and Richard B. Frankel of California Polytechnic State University, San Luis Obispo.
