The two new species of bacteria found growing on the walls of the Roman tombs may help protect our cultural heritage monuments, according to research... The Catacombs of Saint Callistus are part of a massive graveyard that covers 15 hectares [37 acres], equivalent to more than 20 football pitches. The underground tombs were built at the end of the 2nd Century AD and were named after Pope Saint Callistus I. More than 30 popes and martyrs are buried in the catacombs. "Bacteria can grow on the walls of these underground tombs and often cause damage," said Professor Dr Clara Urzì...