Eastern Mediterranean sapropels are organic-rich sediment layers formed every 21.000 years due to climate fluctuations that result in deep-water anoxia. Sapropels were shown to harbor a higher number of active microorganisms in comparison to adjacent sediment layers.
(Coolen et al. 2002)
After "Meteor cruise M51-3" (Overmann et al. 2003), a unique culture collection from sapropel-bearing sediments was established applying optimised cultivation techniques (Süß et al, 2004). A molecular-guided cultivation lead to an increasing cultivation efficiency (Süß et al. 2007b).
The culture collection comprises typical marine bacteria but also microrganisms that were supposed to have a terrestrial origin (e.g. Rhizobium radiobacter). Due to our quantitative molecular investigations we have determined that R. radiobacter counts for up to 5% of all bacteria in sapropels. This was the first study to demonstrate the in-situ abundance of a cultivated deep-biosphere bacterium (Süß et al. 2006).
The phylogenetic variety of the detected isolates suggests a high microbial diversity within Mediterranean sapropels. Furthermore, we have shown that distinctive subpopulations of single species were formed and established there (Süß et al. 2007a). Therefore, we conclude that Eastern Mediterranean sapropels are populated by dynamical and highly diverse microbial communities.
Detailed cruise report
Süß, Jacqueline (2006) Dissertation: "Kultivierungsabhängige Analyse mikrobieller Gemeinschaften in Sapropelen des östlichen Mittelmeeres"
Süß J, Herrmann K, Seidel M, Cypionka H, Engelen B, and Sass H (2008) Two distinct Photobacterium populations thrive in ancient Mediterranean sapropels. Microb Ecol 55:371-383
Süß J, Schubert K, Sass H, Cypionka H, Overmann J, Engelen B (2006) Widespread distribution and high abundance of Rhizobium radiobacter within Mediterranean subsurface sediments. Environm Microbiol 8:1753-1763
Süß J, Engelen B, Cypionka H, Sass H (2004) Quantitative analysis of bacterial communities from Mediterranean sapropels based on cultivation-dependent methods. FEMS Microbiol Ecol 51:109-121
Overmann J, Schubert K, Hoffelner H, Engelen B (2003) Characterization of Bacteria in Sapropels, in Overlaying Sediments and Water Layers by a Multidisciplinary Approach. In: Hemleben C, Hoernle K, Jørgensen BB, and Roether W (Eds.), 2001, Ostatlantik - Mittelmeer - Schwarzes Meer, Cruise No. 51, 12 September - 28 December 2001. METEOR-Berichte, Universität Hamburg, 03-1, 225 pp. 3-32 - 3-40, ISSN 0936-8957
Coolen MJL, Cypionka H, Sass A, Sass H, Overmann J (2002) Ongoing modification of Mediterranean Pleistocene sapropels by green nonsulfur bacteria and crenarchaeota. Science 296:2407-2410