(Photo courtesy of Arizona State University)

Outcrop of antibacterial blue clay and elemental sulfur (yellow) in a volcanic sulfide deposit.

(Photo courtesy of Arizona State University)

E.coli bacteria cluster, showing attack of the bacterial membrane (yellow).

(Photo courtesy of Arizona State University)

Researchers unearth a natural clay deposit with antibacterial activity.

Clay has long been thought to contain medicinal properties, prompting people to take mud baths at southwest resorts or even ingesting small amounts. But new research suggests particular types of clay containing certain elements may directly kill harmful bacteria.

Unfortunately, much of the red clay abundant in the southwest, which contains oxidized iron giving it a rust color, isn’t the medicinal clay. Rather, ASU researcher Lynda Williams said green and blue clays have chemically reduced iron, something bacteria needs little bits of to survive.

“So what you see exposed at the surface may be a red looking clay in Arizona, but deep underground it might become more reduced," Williams said. "And what we found is that it is the reduced iron that becomes soluble when you add water to the clay. That, along with aluminum, attacks human pathogens.”

Williams said when the reduced iron clays touch bacteria, the iron and aluminum act in tandem to invade the cell, much like a Trojan horse.

“These clays do a double attack using the aluminum to damage proteins  in the cell wall that opens up the pores and allows excess iron to go into these cells," said Williams. "It’s causing an oxidation reaction inside the cell and causes damage to the interior proteins.”

Fortunately, humans cells get mineral nutrients and oxygen from blood while bacteria cells are dependent on external sources, which is why human cells are not hurt from clay applications.  During initial tests, Williams found the clays were performing better than antibiotics.

“They were killing antibiotic resistant bacteria and bacteria that have no antibiotic cure," Williams said. "So clearly they were working by a different mechanism than normal antibiotics and so if we can know this mechanism, we can synthesize it to make, hopefully, a better drug.”

Which is one of the hopes of Enriqueta Barrera from the National Science Foundation, which the funded the research.

“To be able to understand how it is that it promotes healing with the fast application of clay, this has the potential to have a practical application," said Barrera. "But I think that with more trials and more experiments, it could become applicable, maybe even commercial. ”

Barrera said the foundation funded the research because it’s interdisciplinary approach lets scientists better understand the natural formation of the clays and its toxicity to bacteria.

“You borrow from one discipline and the other and you begin to emerge with a new image of how things operate in nature. And there are actually lots of natural substances that have a use in medicine but sometimes the medical profession doesn’t really know how it operates," said Barrera.

By merging geochemistry with health, it may take soaking in a mud bath from a resort activity to an important treatment against antibiotic-resistant bacteria.

Updated 1/12/2016 at 12:20 p.m.