Halophilic bacteria on ancient parchments

The purple spots on the manuscript above can be blamed on halophilic marine organisms, even though the scroll had not been near the sea.

...the spots are similar to ones that mar parchments made of animal skins all over the world, said Luciana Migliore, an ecotoxicologist at the University of Rome Tor Vergata...

The goatskin scroll, which dates to A.D. 1244, has purple dots all along its margins, and the first and last pages are entirely obscured by the mystery pigment. Migliore's team sampled a few millimeter-size bits of the scroll that had already flaked off...

The genetics told a two-stage story of damage: First, salt-loving, or halophilic, bacteria colonized the parchment. Next, salt-tolerant microbes, particularly the Gammaproteobacteria, took over. What shocked Migliore is that so many of these microbes were marine or aquatic.

But when they took into account how skin scrolls were made, the discovery made sense, Migliore said. The first step after removing the hide from an animal was to bathe the skin in a sea-salt bath to help preserve it, she said. This bath would have killed off most microbes that eat away at flesh — but it also introduced salt-loving and salt-tolerant marine bacteria...

Eventually, though, those salt eaters would have seen their supply run out and died off. Their corpses, Migliore said, provided a whole new source of food for the next phase of bacterial colonization. The Gammaproteobacteria moved in and ate not only the dead halophilic bacteria but also the fine collagen matrix of the goatskin parchment. This caused parts of the parchment to flake off, lost forever.

Salt curing is one thing that skin parchments around the world have in common...

You learn something every day.  More details about this at Live Science.

Photo credit: G. Vendittozzi.