A
Harvard expert in cultural heritage microbiology, investigates a “fingerprint”
left by ancient Egyptian microbes
Cambridge, Mass, June 8, 2011 - In the
tomb of King Tutankhamen, the elaborately painted walls are covered with dark
brown spots that mar the face of the goddess Hathor, the silvery-coated
baboons—in fact, almost every surface.
Despite almost a century of scientific
investigation, the precise identity of these spots remains a mystery, but
Harvard microbiologist Ralph Mitchell thinks they have a tale to tell.
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 of King Tut's death,
Mitchell thinks those brown spots reveal something: that the young pharaoh was
buried in an unusual hurry, before the walls of the tomb were even dry.
Like many ancient sites, Tutankhamen's
tomb suffers from peeling paint and cracking walls. In the oppressive heat and
humidity, throngs of tourists stream in and out of the cave, admiring it but
also potentially threatening it.
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, the Gordon
McKay Research Professor of Applied Biology at Harvard's School of Engineering
and Applied Sciences (SEAS), combines classical microbiology with cutting-edge
genomic techniques. His research team has been culturing living specimens
swabbed from the walls of the tomb as well as conducting DNA sequence analyses.
Meanwhile, chemists at the Getty have been
analyzing the brown marks, which 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," says 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 in 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," explains Mitchell. "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, he says, until the tomb eventually dried out.
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. Nick Konkol, a former postdoctoral research
associate, and Alice DeAraujo, a current research assistant, have developed
rapid new ways to detect mold growing within the paper of historical
manuscripts, paintings, and museum artifacts.
The field is referred to as "cultural
heritage microbiology," and Mitchell literally wrote the textbook on it.
For microbiologists with broad interests,
cultural heritage provides an endless supply of surprising, 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," Mitchell says.
Just a few years ago, he 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 says. "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 says.
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