This post is lazily reposted from Wired…
“There’s a voracious bacterium nibbling on Italy’s priceless cultural relics — and historians are shouting, “Bravo!” Over the centuries, air pollution has formed a thin black crust on the stone surfaces of statues and buildings, and Desulfovibrio vulgaris vulgaris is being used to remove that crud in a very Italianate fashion: by eating it. Unleashed on works of art and architecture, the bacteria metabolize the sulfate in the crust, converting some of it into — oh, please excuse them — gasses. So far, microbiologist Claudia Sorlini and her team at the University of Milan have applied the biotreatment to parts of their home city’s gothic Duomo and Michelangelo’s Pietà Rondanini. Next, Sorlini says, she’s itching to let her peckish little friends gorge themselves on Notre Dame.”
From Wired
This was actually started in Vermont and reported in 2003:
http://www.abc.net.au/science/news/stories/s886276.htm