Karin Hammer is involved in research concerning vira, attacking bacteria. These vira, named bacteriophages or short “phages”, is a potential danger for bacteria. Some phages will always kill the bacterium, while others – the temperate phages- may choose whether they kill the bacterium or infect it without destroying its continued growth, and hence its genome is replicated when the bacterium divides. These phages therefore present very interesting mechanisms of gene regulation, which is investigated by the DTU group.

The ability of the phages to kill bacteria is still a problem for the dairy industry, using lactic acid bacteria as starter cultures for e.g. cheese production. We are therefore investigating the mechanisms used by bacterial mutants being resistant to phage attack. On the other hand phages may also be used for deliberate killing of pathogenic bacteria, being resistant to many antibiotics, this is called phage therapy. For this purpose it is important to know how to avoid bacterial mutants developing resistance to the phages used.

Phages are able to transfer genes from one bacterium to another in nature. Knowlegde about phage infection and transfer is therefore very important. It is also now known that pathogenic bacteria often contains several temperate phages inserted into their genomes and in addition that these phages contain genes making the bacterium more pathogenic than its relative without the phage.