Phages infecting Flavobacterium strains isolated from Swedish lakes

Sammanfattning

Bacteria play many roles in ecosystems worldwide. It is still largely undiscovered how their interactions lead to eco-evolutionary impacts. Flavobacterium have many strains that act as pathogens against fish which has consequences both in natural habitats and fish farms. Phage therapy could be a possible application to gain control over the problematic bacterial cultures. The aim of this study is to capture and study phages for different Flavobacterium strains. Phages and bacteria collected from the lakes Ekoln and Erken in Sweden were used in this study. Different strains of Flavobacterium were compared using their 16S rRNA gene sequence similarity. Five representatives were chosen to establish a diversity in the studied strains. Growth cycle of these strains was defined, and they were used for phage isolation. The phage infection treatments were observed through cell counts using flow cytometry to detect potential infections. A total of six treatments had a confirmed infection with repeatability in transfers. Samples of the treatments were observed with transmission electron microscopy (TEM) and one phage was confirmed. Measurements of flow cytometry showed a possible span of time where the time of infection occurs. Possible detection of an arms race between infection and development of resistance can also be noted. This can be seen as a decrease in cell count in the treatment which later recovers to a count similar to the control. Six confirmed phages was visualized through TEM, showing a morphology of a capsid head and for one phage a long tail. Further studies are needed to analyze phage diversity and clear dynamics of phage infection on freshwater Flavobacterium strains.