The Baltic Sea is an intra-continental basin that has undergone alterations between limnic, brackish and marine conditions due to repeated glaciation and sea-level changes in the past. The sediments represent an archive of this paleoenvironmental history. Recently, sediments from the Baltic Sea were recovered during IODP Exp. 347 with the aim to identify the impact of the dramatic variations in salinity on the microbial communities within the deep subsurface.
In the this project, we will focus on viruses and their host organisms as relevant components of the deep biosphere. As viruses control microbial populations and mediate enhanced carbon turnover due to lysis of infected host cells, they have a major impact on microbial and biogeochemical processes.
In our previous investigations, viruses have been detected in sediments as old as 14 Ma and as deep as 320 mbsf. Increasing virus-to-cell ratios with depth indicated ongoing viral production in the deep subsurface. However, as only little is known about general characteristics of benthic viruses, in this project, we will investigate viral production, decay, life modes and induction mechanisms in Baltic Sea sediments.
We will directly measure rates of viral production and further determine if salinity changes triggered the induction of prophages in the past. By analyzing different sediment layers, enrichment cultures and isolates, we will determine if this variation has influenced prokaryotic and viral communities' structures. With our study, we will gain deeper insights into the impact of viruses on current subsurface communities and their role during the paleoenvironmental history of the Baltic Sea.
Oscar Chiang (PhD student)
Engelen B, Engelhardt T, Cypionka H (2014) Phagen in Sedimenten der marinen
tiefen Biosphäre. Biospektrum 04.14:380-382, DOI: 10.1007/s12268-014-0451-0
Engelhardt T, Kallmeyer J, Cypionka H, Engelen B (2014) High virus-to-cell ratios indicate on-going production of viruses in deep subsurface sediments. ISME J 8:1503–1509
Engelhardt T, Sahlberg M, Cypionka H, Engelen B (2013) Biogeography of Rhizobium radiobacter and distribution of associated temperate phages in deep subseafloor sediments. ISME J 7:199-209
Engelhardt T, Sahlberg M, Cypionka H, Engelen B (2011) Induction of prophages from deep-subseafloor bacteria Environm Microbiol Rep 3:459–465