Finished bachelor projects:

Effects of increased hydrostatic pressure on microbial denitrification.

• project type: Bachelor, 15 ECTS
  Student Niels Peter Jørgensen
  Supervisor: Ronnie N. Glud
  Start: 1 February 2021
  End: 1 august 2021

Studies show that hydrostatic pressure have a decreasing effect on the rate of different microbial process like the breakdown of organic matter. Most studies so far have focused on aerobic processes, and it is to a large extend still unknown how hydrostatic pressure affects anaerobic processes even though they are important factors for the breakdown of organic matter in the oceans. The denitrification process is of particular interest because it removes bio available nitrogen, which is often a limiting nutrient, from the ocean by converting it into free nitrogen gas which can then diffuse out of the water column.

To get a better understanding of this we will bring sediment form Aarhus bay under elevated pressure for different amounts of time and via the Isotopic parring technique see if the denitrification rate changes over time. This will at the same time answer if there in costal sediments even exist microbes capable of adapting to elevated pressure conditions.

Isolation of novel virus-host systems from hadal environments

• Project type: Bachelor, 15 ECTS
  Student: Amalie Elisabeth Schønemann
  Supervisor: Mathias Middelboe
  Start: 1. February 2021
  End: 15. June 2021

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.
For an in depth understanding of how life is shaped by hadal conditions, we need good model systems of organisms that can live and perhaps even thrive under such extreme conditions. Furthermore, cultured representatives provide valuable validation and reference material for sequence-based data and for quantifying biologically driven processes. As hadal ecosystems harbor a vast and unknown diversity of microbial and viral life, we are interested in isolating new bacteria and viruses specifically from hadal environments.
This project will be undertaking a large isolation and culturing effort from hadal sediment samples, and for comparison isolation will be done in parallel on sediment samples collected from a marine, coastal ecosystem.

Hadal virus-host system potentially specialized in chitin degradation

• Project type: Bachelor, 15 ECTS
  Students: Marie Golan and Maja Ek Jensen
  Supervisor: Mathias Middelboe
  Start: 1. February 2021
  End: 15. June 2021

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.