(Table T1) Total procaryotes, and living bacteria and archaea in black shales of ODP Leg 207 sites

Subseafloor sediments harbor over half of all prokaryotic cells on Earth (Whitman et al., 1998). This immense number is calculated from numerous microscopic acridine orange direct counts (AODCs) conducted on sediment cores drilled during the Ocean Drilling Program (ODP) (Parkes et al., 1994, doi:10.1038/371410a0, 2000, doi:10.1007/PL00010971). Because these counts cannot differentiate between living and inactive or even dead cells (Kepner and Pratt, 1994; Morita, 1997), the population size of living microorganisms has recently been enumerated for ODP Leg 201 sediment samples from the equatorial Pacific and the Peru margin using ribosomal ribonucleic acid targeting catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) (Schippers et al., 2005, doi:10.1038/nature03302). A large fraction of the subseafloor prokaryotes were alive, even in very old (16 Ma) and deep (>400 m) sediments. In this study, black shale samples from the Demerara Rise (Erbacher, Mosher, Malone, et al., 2004, doi:10.2973/odp.proc.ir.207.2004) were analyzed using AODC and CARD-FISH to find out if black shales also harbor microorganisms.