Scientists Discover How Bacteria Dispose of Toxic Metals

It’s no mystery that medicine is fighting a losing battle when it comes to bacterial infections. According to a study by the Centers from Disease Control, rates of infection of a particularly nasty bacteria (MRSA) doubled between 1998 and 2007. The trouble is that bacteria multiply very rapidly. The cycle goes something like this. Scientists invent a new antibiotic that seems to work very well; maybe it kills 99% of the bacteria it comes across. That antibiotic is given out in hospitals and pharmacies (sometimes overprescribed for viral infections, against which an antibiotic is useless). The antibiotic does it’s job and kills 99% of the harmful bacteria.

However, 1% of the bacteria lived. They had something in their genetic makeup – a mutated gene, or maybe an adaptation that the others didn’t possess – that allowed them to survive that antibiotic. Those bacteria multiply rapidly. Now, that 1% that was immune to the antibiotic has spread everywhere, and the antibiotic is useless. Scientists have to develop another antibiotic, and maybe this one has more side effects for the patient. The cycle continues.

Very recently however, a publication in the journal Nature – arguably the most prestigious science journal in the world – scored a major victory for pharmaceutical companies who design new antibiotics. Chemists from the Argonne National Laboratory were able to purify and crystallize a portion of some E. Coli bacteria. It was a victory just to reach this goal, as proteins are notoriously difficult to crystallize. The section they crystallized was the membrane that surrounds the bacterium. The chemists then examined the crystalline sample using X-ray crystallography, which gave them a computerized 3-D image of precisely how the bacterial membrane “pumps” out toxic heavy metals like copper and silver that make it into the cell of the bacteria.

Now that we have this knowledge of how the bacteria is able to rid itself of these harmful materials, and we have a picture of the precise “pump” mechanism that is responsible, chemists can design molecules which will “plug up” these pumps from the outside of the bacterial membrane. They can then design antibiotics which contain copper and silver, which are lethal to E. Coli bacteria if the bacteria isn’t able to quickly pump the metal back out of itself. With the exits blocked, the bacterium will die. It’s an entirely new approach to antibiotics, and it’s not something to which the bacteria can easily adapt. It would require a reconfiguration of it’s entire waste disposal system to “get around” this new strategy. It’s definitely a substantial victory for chemists and bacterial researchers everywhere, and it’s certainly worthy of a publication in Nature.

The source of this article can be found at:

Feng Long, Chih-Chia Su, Michael T. Zimmermann, Scott E. Boyken, Kanagalaghatta R. Rajashankar, Robert L. Jernigan, Edward W. Yu. “Crystal structures of the CusA efflux pump suggest methionine-mediated metal transport”. Nature, 2010; 467 (7314): 484.

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