Deep sea viruses: Hadal virus-host system potentially specialized in chitin degradation

Main area:Marine biology
Target group:Biology, Biochemistry, Bioinformatics
Educational level:Masters, Bachelor
Project description:

The deep hadal trenches (Water depths >6.000 m) are the most remote parts of the global ocean, representing some of the most extreme and scantly explored habitats on Earth. Hadal trenches are also likely hotspots of organic matter deposition fueling biogeochemical cycling in largely unexplored marine ecosystems. Viruses are a key mortality agent in microbes and their predation on microbes impact food web structures and biogeochemical cycling.

Recently, we documented 5]10 times higher virus densities and extensive spatial variation in hadal sediments as compared to adjacent abyssal sites, suggesting that viruses play a prominent role for microbial mortality and biogeochemical cycling in hadal environments. In a new research project we quantify the phylogenetic diversity and composition of hadal benthic microbial and viral communities, identify active microbial players, and quantify the role of viruses in microbial mortality and element cycling.

We have successfully isolated a virus-host system from Kermadec Trench sediment, which we now have in culture in the lab. Of particular interest is two different functional genes, one is found on the host genome and the other sits on the phage genome, both genes encode for a chitinase. Chitinases are hydrolytic enzymes which facilitate the breakdown of chitin and its derivatives. Preliminary experiments indicate some interesting interactions between the presence of chitin and the prophage and that a small fraction of the host population does not carry the prophage, which suggests a trade-off between the pro-phage and chitin degradation.

This project will carry out experiments to characterize growth dynamics of the host with and without prophage and with and without chitin in order to quantify the trade-off of carrying the prophage. We also want to further characterize the activity of the two different chitinases under different conditions (high pressure and low temperature) which will give important insights to microbial activity and turnover rates of organic material in hadal systems.

Methods used:Microbiology, Molecular biology
Keywords:Deep sea, Bacteriophage-host interactions, viral diversity, Prophages
Supervisor(s):  Mathias Middelboe, Sachia Jo Traving