Impact of salinity changes on viral production during the paleoenvironmental history of Baltic Sea sediments
Microbial Ecology and Applied Microbiology
Final Report Abstract
Deep subsurface sediments of the Baltic Sea represent a paleoenvironmental archive of this intracontinental basin which has undergone alterations between limnic, brackish and marine conditions in the past. The overall goal of IODP Exp. 347 was to investigate the impact of these environmental changes on benthic microbial communities. In this context, the aim of our project was to identify the response of viruses and their host bacteria to changing salinities. As a prerequisite, we have developed a fast and accurate protocol for counting of viruses by flow cytometry. The method worked for culture media and surface sediments of tidal flats, but unfortunately failed for the more challenging deep subsurface samples of the Baltic Sea. As the sediment material is preserved at -80 °C, we are probably still able to perform the virus quantification by using a newly developed protocol that is currently established in our laboratory. Due to the described difficulties, we started to focus more on the host bacteria. From our cultivation experiments, we have obtained a total of 36 isolates of which 14 were genome sequenced. While three of them were validly described as new species (Desulfosporosinus nitroreducens, Desulfosporosinus fructosivorans, Labilibaculum filiforme) two isolates (Labilibaculum manganireducens, Marinisporobacter balticus) even represented new genera. Physiological analysis revealed considerable differences in their salt tolerances, which might be beneficial for their survival in deep subsurface sediments of the Baltic Sea. Different viruses have been identified in the isolates, which can be either induced by mitomycin or a produced at high numbers during growth of the bacteria. From the genome information of six Vibrio diazotrophicus strains, we were able to design specific primers for the highly conserved zot-gene. The primers were used to quantify Vibriophages in our cultures and also in the Baltic Sea samples. In conclusion, we only obtained some hints to identify the role of viruses during the paleoenvironmental history of the Baltic Sea. However, as there is still a lack of deep subsurface isolates, our strains are now available for the scientific community to further study their physiological features which might be specific for their unique habitat.
Publications
- (2017) Marinisporobacter balticus gen. nov., sp. nov., Desulfosporosinus nitroreducens sp. nov. and Desulfosporosinus fructosivorans sp. nov., new spore-forming bacteria isolated from subsurface sediments of the Baltic Sea. Int J Syst Evol Microbiol, 67:1887-1893
Vandieken V, Niemann H, Engelen B, Cypionka H
(See online at https://doi.org/10.1099/ijsem.0.001883) - (2017) Virus dynamics are influenced by season, tides and advective transport in intertidal, permeable sediments. Front Microbiol 8:2526
Vandieken V, Sabelhaus L, Engelhardt T
(See online at https://doi.org/10.3389/fmicb.2017.02526) - (2018) Draft genome sequences of six Vibrio diazotrophicus strains isolated from deep subsurface sediments of the Baltic Sea. Genome Announcements 6:e00081-18
Castillo D, Vandieken V, Engelen B, Engelhardt T, Middelboe M
(See online at https://doi.org/10.1128/genomeA.00081-18) - (2018) Labilibaculum manganireducens gen. nov., sp. nov. and Labilibaculum filiforme sp. nov., novel Bacteroidetes isolated from subsurface sediments of the Baltic Sea. Front Microbiol 8:2614
Vandieken V, Marshall IPG, Niemann H, Engelen B, Cypionka H
(See online at https://doi.org/10.3389/fmicb.2017.02614)
