June 9, 2011

Ancient Microbes Reveal Speedy Burial Of King Tut

A Harvard expert in cultural heritage microbiology reports that a "fingerprint" left behind by ancient Egyptian microbes might indicate that King Tut's burial was conducted hastily.

The pharaoh's tomb includes elaborately painted walls covered with dark brown spots that mar almost every surface.  However, despite nearly a century of scientific investigation, the precise identity of these spots remains a mystery. 

So Harvard microbiologist Ralph Mitchell set out to find an explanation.

Nobody knows why Tutankhamen, the famed "boy king" of the 18th Egyptian dynasty, died in his late teens.  Various investigations have attributed his early demise to a head injury, an infected broken leg, malaria, sickle-cell anemia, or perhaps a combination of several misfortunes.

Whatever the cause, Mitchell believes those brown spots reveal that the young pharaoh was buried in an unusual hurry, before the walls of the tomb were even dry.

Like many ancient sites, King Tut's tomb suffers from peeling paint and cracking walls due to oppressive heat and humidity and streams of tourists.

Concerned about the tomb's preservation, the Egyptian Supreme Council of Antiquities approached the Getty Conservation Institute for help. The Getty, in turn, had questions for Mitchell.

What are the brown spots? Are visiting tourists making them worse? Most importantly, do they present a health hazard?

In his investigation, Mitchell, Professor of Applied Biology at Harvard's School of Engineering and Applied Sciences, combined classical microbiology with leading-edge genomic techniques.  His research team cultured living specimens swabbed from the walls of the tomb and conducted DNA sequence analyses.  Meanwhile, chemists at the Getty analyzed the brown marks that have seeped into the paint and the plaster at the molecular level.

So far, the chemists have identified melanins, which are characteristic byproducts of fungal (and sometimes bacterial) metabolism, but no living organisms have yet been matched to the spots.

"Our results indicate that the microbes that caused the spots are dead," said Archana Vasnathakumar, a postdoctoral fellow in Mitchell's lab.

"Or, to put it in a more conservative way, 'not active.'"

Further, analysis of photographs taken when the tomb was first opened in 1922 shows that the brown spots have not changed at all during the past 89 years.

While the identity of the ancient organism remains a mystery, all of this is good news for tourists and Egyptologists alike, because the evidence suggests that not only are the microbes not growing"”they're actually part of the history, offering new clues to the circumstances of King Tut's death.

"King Tutankhamen died young, and we think that the tomb was prepared in a hurry," Mitchell said.

"We're guessing that the painted wall was not dry when the tomb was sealed."

That moisture, along with the food, the mummy, and the incense in the tomb, would have provided a bountiful environment for microbial growth, until the tomb eventually dried out, he said.

Exotic as the project may sound, investigations like this are typical of Mitchell's research in applied microbiology.

In past years, his lab has studied the role of bacteria in the deterioration of the USS Arizona at Pearl Harbor, Hawaii, and the microorganisms living within limestone at Mayan archaeological sites in southern Mexico.

The field is referred to as "cultural heritage microbiology," and it is providing an endless supply of new applications, crossing disciplines and cultures and providing important insight into modern environmental problems.

"This type of research is typical of the interactive activity of SEAS, where modern scientific and engineering techniques are integrated to solve complex problems," said Mitchell, who literally wrote the textbook on the field.

Just a few years ago, Mitchell was called down to the Smithsonian National Air and Space Museum to investigate the collection of Apollo space suits.  In the heat and humidity of the museum's Maryland storage facility, black mold was chewing through the many-layered polymers, damaging the priceless suits.

The relatively simple solution in that case was the installation of a climate control system.  Unfortunately, however, there is a difference between prevention and treatment. Once a historical artifact has begun to deteriorate, the damage is usually irreversible.

Mitchell points to the example of the cathedral in Cologne, Germany. Built over the course of 632 years and listed as a UNESCO World Heritage site, the walls of the magnificent cathedral feature angels and historical figures carved out of stone.

In just the past 100 years, the angels' faces have been eaten away by air pollution.

"I always use the analogy of cancer," Mitchell said.

"You want to get to it early enough that it isn't doing major destruction."

But what to do about King Tut's 3000-year-old microbial vandalism?

The damage is already done, so Mitchell predicts that the conservators will want to leave the spots alone, particularly as they are unique to that site.

"This is part of the whole mystique of the tomb," he said.


Image 2: Ralph Mitchell in his lab at the Harvard School of Engineering and Applied Sciences. Mitchell, an expert in cultural heritage microbiology, believes that a "fingerprint" left by ancient Egyptian microbes may reveal a new secret about King Tut's burial. Credit: Eliza Grinnell, Harvard School of Engineering and Applied Sciences


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