Isolation of lysogenic phages from potentially pathogenic Vibrio species

Antje.Wichels [ at ]


In the wake of global warming seawater temperatures in temperate waters increased over the past decades. In consequence, many bacterial species can proliferate successfully in those for-mer cold habitats, increasing drastically in abundance. But the emergence of microbial commu-nities embraces not only harmless but also pathogenic genera, entailing severe consequences for human infections. Especially several pathogenic species of the genus Vibrio may be an in-creasing health risk in the future. Though, not only the temperature related emergence of path-ogenic strains was in the focus of recent studies, but also the origin of new pathogenic strains in the first place. Phages are known to play a key role in the development of new virulent and pathogenic strains. As a result to their vast influence of microbial genome diversification phages have become a prime suspect in the adaptation of new pathogens. Common genomic alterations are caused by lysogenic conversion, a process in which lysogenic phages transfer virulence factors to the bacterial host upon prophage integration. These virulence factors can encode haz-ardous toxins or other beneficial metabolic modifications, increasing the pathogenic potential of the bacteria. Many studies focused on a detailed genomic analysis of lysogenic phages, to understand the evolution of new pathogenic strains and the underlying molecular mechanism. However, due to the fact that the lysogenic phages are commonly integrated within the bacterial genome, phage separation and isolation is a fundamental process for any phage-related study. Thus was the aim of this thesis the isolation of lysogenic phages from potentially pathogenic V. parahaemolyticus strains, to enable a detailed analysis of the phage genome in successive stud-ies. Prophages were detected in two out of 12 strains, via chemical induction. The remaining strains carried either no prophage (inducible with the used methods) or the induction was too inconsistent for further experiments. In general, all strains showed a high intraspecies diversity concerning induction efficiency and growth development. Furthermore, most strains reacted highly sensible towards modulation of particular experimental parameters. Finally the strains with inducible prophages were used to produce large quantities of phage biomass, enabling a detailed characterization of the lysogenic phages in future studies. Only on the basis of phage isolation, possible virulence factors within the phage genome can be identified which might relate to the emergence of new pathogenic Vibrio strains.

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Thesis (Bachelor)
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Schubert, J. (2015): Isolation of lysogenic phages from potentially pathogenic Vibrio species , Bachelor thesis, Universität Würzburg.

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