Esta vez he querido compartir un
artículo muy interesante para profesionales de diferentes áreas (arqueología,
arte, biología). el artículo está copiado textualmente del Blog de Central
Science en el apartado Artful Science (http://cenblog.org/artful-science/2011/06/09/two-faced-microbes-dirty-fungi-and-cleaning-bacteria/).
June 9th, 2011 • 06:06
By Sarah Everts
Microbes can be an ugly
pain-in-the-butt for artifacts.
Even if the bacteria and fungi
growing on heritage buildings, frescoes, space suits and archival documents can
be killed, they often leave behind some rather unpleasant stains that are
really hard to clean off the sensitive surfaces of artifacts. That’s the
situation in King Tut’s tomb, for example, where fungi have left behind dark
brown spots on the beautifully painted walls.
Today the Harvard Gazette
wrote about this issue: At the request of Egyptian heritage officials,
researchers at the Getty
Conservation Institute swabbed the walls of King Tut’s tomb, and sent
samples of the brown muck to Ralph Mitchell, a
Harvard microbiologist who specializes in cultural heritage science. Getty
chemists figured out that the dark spots are actually melanin–the same pigment
that builds up in your skin when you get a tan–while Mitchell’s team figured
out that the fungi are dead and probably won’t be producing any more browny
spots. Mitchell thinks that the fungi initially grew because the tomb was
sealed before the paintings inside were dry, suggesting that the teenage king
was buried in a hurry. The still-wet surface thus provided tempting real-estate
for melanin-producing fungi.
King Tut's tomb with brown spot
stains. © The J. Paul Getty Trust, 2001
It turns out that
melanin-producing fungi have also stained marble in Italian
cathedrals after an ill-advised attempt to protect the marble using acrylic
polymers. The acrylic on the marble attracted the staining microbes who found
the plastic to be a tasty meal. But microbes will also grow on buildings, art
and artifacts that haven’t received unwise “protection.” For example, orangey carotenoid pigments are
often left behind by bacteria on stone buildings, Mitchell says, and frescoes have been stained
rosy red due to the phycoerythrin
pigments produced by cyanobacteria.
The question remains: How does
one remove these unfortunate discolorations?
Mitchell is developing a
technique that uses enzymes to eat away the unpleasant pigments without hurting
the pretty parts below. Think of laundry detergents that advertize enzymes
which can remove stains on your white clothing without doing damage to the
textiles. Mitchell’s strategy obeys the same overall principle… and that’s
about as much information as he was able to give because he’s in the middle of
patenting the enzyme cleaning process.
Cyanobacteria growing on the Luca
Signorelli frescoes in Italy's St. Brizio Chapel caused a rosy discoloration.
Credit: Wikimedia Commons.
So, all this could leave you with
the impression that microbes are only bad for cultural heritage, but here’s a
possible counterpoint: Researchers in Italy and Spain are experimenting
with the idea of using bacteria to clean off the salty crusts that build up
on frescoes.
Sort of weird but true: The
researchers grow Pseudomonas bacteria in a wet gel, and apply it to the
frescoes. The bacteria then get to snacking on the salt scabs found on the
frescoes until there’s no more unsightly crust. You can apparently kill the
bacteria by wiping off the gel. This dries the surface and the bacteria die in
the arid environment.
According to this
press release: They’ve tried it out on frescoes in the 17th century Church
of Santos Juanes in Valencia, Spain, and on Campo Santo di Pisa murals, in
Italy. It’s too early to know whether harnessing microbes as cleaning
work-horses will compete with the other ways to remove salt crusts, such as a
mechanical scraping or nanotechnology.
And the take-home message? The
world of cultural heritage research might be a bit like the human microbiome,
where some of the trillions
of microbes growing in and on you are problem-making pathogens while others
are good guys that help you digest your food.
Using bacteria to clean up
artwork in the Church of Santos Juanes in Valencia. Credit: RUVID
