Name: Bert Engelen

Email: engelen@icbm.de

Author: Bert Engelen*, Tim Engelhardt, Monika Sahlberg, Heribert Cypionka

Author affiliation: Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Germany * Presenting author

Abstract title: Viral infections as controlling factors for the deep biosphere?

Absstract:

The marine deep biosphere represents the largest biotope on Earth. Throughout the last years, we have obtained interesting insights into its microbial community composition. However, one component that was completely overlooked so far is the viral inventory of deep-subsurface sediments. While viral infections were identified to have a major impact on the benthic microflora of deep-sea surface sediments (Danavaro et al. 2008), no studies were performed on deep-biosphere samples, so far. As grazers probably play only a minor role in anoxic and highly compressed deep sediments, viruses might be the main (predators) for indigenous microorganisms. Furthermore, the release of cell components by the viral shunt could have a major impact on the deep biosphere in providing labile organic compounds to non-infected microorganisms in these generally nutrient depleted sediments. In our first phage-induction experiments using mitomycin C, representative isolates from our culture collection obtained from a cruise of the Ocean Drilling Program, ODP Leg 201 (Batzke et al. 2007) were screened for the presence of lysogenic phages. Due to viral lysis, six out of thirteen cultures from various phylogenetic groups, sampling sites and sediment depths showed a drop in cell density and up to 3 x 10^10 VLP/ml. The phage morphology was visualized by transmission electron microscopy (TEM). The study of the viral component within the deep biosphere offers to answer the following questions: To which extent are deep-biosphere populations controlled by viral infections? What is the inter- and intra-specific diversity and the host-specific viral biogeography? Can viral infections tell us something about the physiological state of indigenous microorganisms? Finally, we will obtain estimates for the viral shunt as an important factor for sustaining the deep biosphere. References: Batzke A, Engelen B, Sass H, Cypionka H (2007) Phylogenetic and physiological diversity of cultured deep-biosphere bacteria from Equatorial Pacific Ocean and Peru Margin sediments. Geomicrobiology J 24:261-273 Danovaro R, Dell'Anno A, Corinaldesi C, Magagnini M, Noble R, Tamburini C, Weinbauer M (2008) Major viral impact on the functioning of benthic deep-sea ecosystems. Nature 454: 1084-U1027