All known organisms need iron to survive. All except one - Borrelia burgdorferi, the bacteria that causes Lyme disease, has evolved to use manganese instead.

For almost all organisms, iron is essential in processes like making new enzymes and other proteins. Perhaps the most obvious example is its role in haemoglobin, the oxygen-transporting protein found in the red blood cells of almost all vertebrates. Researchers knew that the bacteria B. burgdorferi did not need iron, but have now discovered that it requires high levels of manganese instead.

The bacteria's use of manganese rather than iron helps explain how it can evade the immune system. One of the immune system's responses against invaders is to lower the amount of iron in the blood. This starves the pathogen of the iron it needs (as well as making us feel terrible) and works against almost every pathogen. But if the invader doesn't need iron, like B. burgdorferi, this attack is quite ineffective.

Antibiotics are currently the only treatment for Lyme disease. Penicillin is generally effective if Lyme disease is caught early, but it works by attacking a bacterium's cell walls - something certain forms of Borrelia don't have. The team behind the study hope knowledge of manganese's role will aid the manufacture of new treatments.

"We'd like to find targets inside pathogenic cell that could thwart their growth," Valerie Culotta (John Hopkins University Bloomberg School of Public Health and involved in the study). "The best targets are enzymes that the pathogens have, but people do not, so they would kill the pathogens but not harm people."

The bacteria's manganese mechanism could be a promising target, and the team's next plan is to map the bacteria's metal-containing proteins and find out how it extracts manganese from its environment.

Credit: CDC/ Claudia Molins photo: Janice Haney