Bacteriophages, phage-host interactions and evolution of defence mechanisms in beneficial bacterium propionibacterium freudenreichii
Bacteriophages (phages) infecting Propionibacterium freudenreichii, a bacterium known for production of active vitamin B12 and for causing well-documented benefits to human health, are more diverse than those identified for closely related genera. At the same time, the defence mechanisms protecting the bacterial strains (hosts) from phage attacks are more diverse as well. These two phenomena suggest that P. freudenreichii strains and their phages have experienced complex interactions in phage-bacterium arms race. However, both phages attacking, and the defence mechanisms that this important food-grade Actinobacterium uses to protect itself from phage attacks are currently severely understudied. In CO-DEfENDENCE, I will use an innovative approach of systematic study of the defence mechanisms not only from the perspective of the bacterium, but also from the perspective of the phage. The use of strains and phages isolated from samples of different origin will ensure diversity of material subjected to analyses by a combination of phenotypic, genomic, proteomic and imaging methods. This multidisciplinary approach is possible due to guidance offered by world-class phage specialists at one of the world’s top universities, the University of Copenhagen. The expected result of CO-DEfENDENCE is elucidation of complex interactions between P. freudenreichii and its phages, which led to the high diversity of the phages and the multitude of defence mechanisms employed by the strains.  As an added benefit, these results have a great potential for being translated into novel genetic tools and to aid the development of phage therapies, especially those aimed at pathogenic Actinobacteria.