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In these epidemic days, it’s easy to paint all microbial organisms in a bad light, but some bacteria are chiseling out a reputation in marble restoration. Over the last year, a team of scientists, historians, and art restorers applied the breakthrough cleaning technique of using a bacterium called Serratia ficaria SH7 to eat away at contaminants in the marble statuary, tombs, and architecture of the chapel designed by Michelangelo to house the remains of Italy’s powerful Medici family.
“It was top secret,” said Daniela Manna, one of the art restorers, quoted in the New York Times, of the decision to use SH7 to address particular areas of the tombs that remained stubbornly resistant to cleaning, even after nearly a decade of restoration efforts. Understandably, as the bacteria-driven cleaning might be alienating, falling as it did just prior to and in the midst of a raging pandemic that hit Italy especially hard in its first wave. Though visitors to the chapel might have been equally skeeved out to learn that some of the toughest stains are thought to be the result of Alessandro Medici, a ruler of Florence, whose corpse had apparently been interred in 1537 without a proper preparation, causing human effluvia to penetrate the surrounding marble. The resulting deep stains and “button-shaped deformations” to the original construction have appeared in descriptions of a sarcophagus in the graceful chapel as early as 1595, and remained impervious to all previous efforts to address them. Additionally, centuries of plaster casts used to replicate Michelangelo’s sculptural details from the tombs left residues that proved intractable over time.
Enter SH7, a bacteria that feasts on glue, oil…and presumably the ancient remains of assassinated royals, leaving the decorative surfaces of the chapel and its statuary gleaming and pristine as they’ve never been within the modern era. The brain trust that analyzed the surface conditions of the tomb included Italy’s National Research Council, which used infrared spectroscopy that revealed calcite, silicate and organic remnants on the sculptures, and Anna Rosa Sprocati, a biologist at the Italian National Agency for New Technologies, who surveyed and tested bacteria from a collection of almost 1,000 strains to find one that would eat the offending phosphates and proteins, but leave the Carrara marble untouched.
After delays due to COVID-19, the New Sacristy chapel is finally restored to gleaming glory by some dedicated researchers and their army of bacteria. The power of these strains to restore has already found some additional applications, with Sprocati using bacteria isolated from a Naples industrial site to clean a marble relief of the Meeting of Attila and Pope Leo in St. Peter’s Basilica in Rome, sullied with wax from hundreds of years worth of candles. Because the non-spore-shedding bacteria helps create a safer environment than requiring art workers to do incredibly delicate work at sometimes perilous heights, one images a great future for this bacteria. It’s heartening to think that even a legacy as influential as that of the Medici family shines a little brighter today with the help of a humble germ.