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. These little microbes huddled in the middle layers of the parchment, where the salinity was just right. When the scroll was read and stored at various monasteries throughout its lifetime, changes in temperature and humidity would have allowed the salt-loving bacteria to grow and thrive. Many of these species produce purple pigments, Migliore noted.
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.
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