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Microbial Magnetism: Researchers Discover a New Magnetic Bacterium

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Date: January 18, 2012

 

Nevada, the Silver State, is known for its mining industry. But University of Nevada, Las Vegas (UNLV) microbiologist Dennis Bazylinski and members of his lab search any body of water anywhere to find new forms of microbial magnetism. And in a basin named Badwater within Death Valley National Park, Bazylinski and his postdoctoral associate, Christopher Lefèvre, found what they were looking for.

In the Dec. 23 issue of Science magazine, Bazylinski and an international team of researchers explain how they were the first to identify, isolate and grow a type of magnetic bacterium that could one day contribute to the emerging biotech and nanotech industries.

Magnetotactic bacteria are simple, single-celled organisms that are found in almost all bodies of water. Like their name suggests, they navigate along magnetic field lines like miniature swimming compass needles. This is due to nano-sized crystals of the magnetic minerals magnetite (composed of iron and oxygen) or greigite (composed of iron and sulfur) that they produce inside their cells. The presence of these magnetic crystals makes the bacteria and their internal crystals (called magnetosomes) desirable for a large number of commercial applications including drug delivery and enhancement of medical imaging.

While many magnetite-producing bacteria can be grown and relatively easily studied, Bazylinski and his team were the first to cultivate a greigite-producing species.

"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 more than 30 years experience studying magnetotactic bacteria. "Greigite, which is 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."

The greigite-producing bacterium, called BW-1, was found in water samples collected more than 280 feet below sea level in Badwater Basin. The bacterium was later isolated and grown by Lefèvre and Bazylinski at UNLV.

BW-1 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," said Bazylinski.

The study, "A Cultured Greigite-Producing Magnetotactic Bacterium in a Novel Group of Sulfate-Reducing Bacteria," 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 Lefèvre 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 Pósfai of the University of Pannonia (Hungary); Tanya Prozorov of Ames Laboratory; and Richard B. Frankel of California Polytechnic State University, San Luis Obispo.

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