1 1 2 3 4 5 6 7 8 9 217,000 year-old DNA sequences of green sulfur bacteria in Mediterranean 10 sapropels and their implications for the reconstruction of the 11 paleoenvironment 12 13 14 15 16 Marco J.L. Coolen 1 and Jörg Overmann 2 * 17 18 19 1 Woods Hole Oceanographic Institution, Department of Marine Chemistry and Geochemistry, 20 Woods Hole, MA 02543, USA 21 22 2 Section Microbiology, Ludwig-Maximilians-Universität München, Maria-Ward-Str. 1a, D- 23 80638 München, Germany 24 25 26 Running title: Fossil DNA sequences of green sulfur bacteria 27 28 Keywords: ancient DNA, oceanic anoxic events, Chlorobiaceae, fossil DNA, green sulfur 29 bacteria, sapropels 30 31 32 33 34 35 *For correspondence. Email j.overmann@lrz.uni-muenchen.de; Tel. +49-(0)89-2180-6123; Fax 36 +49-(0)89-2180-6125 37 38 39 40