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Diaranson, 27 October 2021 AWEMainta.com 21

Single-cell organisms billions of years old are being used to clean

grime from famous works of art and strengthen marble in monuments

Rome may be the eternal city, but its ancient artifacts are under
unrelenting assault by the ravages of time, pollution, acid rain and
the sweat and breath of millions of tourists. The Arch of Septimius
Severus in the Roman Forum, for one, has the grime of 18 centuries
caked onto its surface.

Now, conservator Alessandro Lugari and his colleagues are trying
to salvage the city's treasures using a new technology -- one that
employs one of the oldest forms of life: bacteria

“This marble was almost disintegrating; it was turning to powder,”
he says. “So we needed to intervene with consolidation.”

Standing beneath the arch, Lugari points to a marble block weighing
several metric tons. “Inside, there are billions of bacteria,” he adds.
The block in question served as a test for the rest of the monument.
Its exterior was covered with enzymes, drawing the bacteria --
which naturally reside within the marble -- to the surface. The
resulting calcification strengthened the stone, with the enzymes “They found that they had to remove both organic and inorganic
applied multiple times a day over the course of two weeks. materials,” says Chiara Alisi, a microbiologist with the Italian National
Agency for New Technologies, Energy and Sustainable Economic

“(The bacteria) doesn’t pass through the marble but rather through Development. “But in this case using chemical substances would have
the cracks, and it solidifies,” Lugari explains. “It becomes covered been too aggressive, so (the restorers) asked for our help.”
with calcium carbonate, which is the same substance as marble
and therefore binds, on a microscopic level, the various parts of Alisi and her team search for potentially useful strains of bacteria in
the marble, creating more marble. industrial waste sites, abandoned mines and sites from the distant past,
“We tried this, it worked, so the next step will be to try it on the like ancient tombs.
entire monument,” he adds. “They’ve already been selected by nature to develop potential abilities,
which we can test, and study and apply,” she explains.

Restoring at the molecular level
Silvia Borghini, conservator at the National Roman Museum, said It’s a complicated process -- isolating individual strains that thrive on
that bacteria have an unfair reputation because they are associated the right kinds of filth, sequencing their DNA and then putting them to
with infection, but their functions are much more complex. “Only work.
a very small number of bacteria are pathogens,” she says. “More
than 95 percent of bacteria are not harmful to humans... we live in Borghini demonstrates the results in the garden of the National Roman
the midst of bacteria and live thanks to bacteria.” Museum. With a toothbrush she removes gel suffused with bacteria
from a block of marble, once part of a 4th-century Roman bridge. Out

Increasingly, restoration work is being carried out on a molecular of the test strips, each of which tried different bacteria strains, the
level. But in Italy, the challenge is huge because the country has cleanest was covered for 24 hours with one known as SH7.
archaeological sites on a monumental scale.
Beginning in November 2019, bacterial microbes were used in "(Bacteria is) easy to apply, and afterwards the artifacts stay clean," she
Florence to clean the Medici Chapel, a mausoleum designed by says. "It doesn't harm the environment, it's not toxic for us or the flora
Michelangelo in the 16th-century. in the garden. It's perfect.

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