Individual study activities

Viruses play major roles in marine environments where they contribute to bacterial mortality and biogeochemical cycling. Little is known about the effects of pressure on virus-bacteria interactions, such as the induction of prophages and viral production from lytic infections. The aim of the current project is to quantify viral production in a marine sediment, in response to hydrostatic pressure along gradients from 1 to 1000 bars, during short term incubations in pressure chambers. Based on sediment samples from a muddy sediment in Øresund, slurries will be prepared with 1 ml surface sediment (0-1 cm horizon) diluted 1:10 with virus-free bottom water in 10 ml exetaines. The exetainers are incubated in 5 replicates at pressure range covering 1, 200, 400, 600, 800, and 1000 bars for ca 12 h. Samples will be collected for quantification of viruses and bacteria at T=0 and t=12 h. 

The expected increase in free viral particles in the sediment slurries is the combined result of prophage induction and lytic viral production. To provide a measure of the potential for prophage induction in the sediment, and the effects of pressure on that process, a parallel experiment will be established, where the number of free phages will be quantified after exposure to Mitomycin C, an artificial agent stimulating prophage induction in bacterial cells. By quantifying prophage induction in parallel sediment slurries with Mitomycin C across the same pressure gradient as above, we will examine the 1) the number of inducible prophages in the microbial population and 2) the effects of pressure on prophage induction.