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Prof. Fabian Commichau, University of Hohenheim: Heat brings light into the lysogeny-lysis decision system of the Bacillus subtilis SPβ prophage

Speaker Series. Abstract: The temperate phage SPβinfects the endospore-forming Gram-positive bacterium Bacillus subtilis and resides as a prophage in its genome. Cultures of B. subtilis that are lysogenic for SPβ release the glycopeptide sublancin, which inhibits the growth of SPβ-free B. subtilis strains by interfering with DNA replication and transcription. Thus, SPβ is a host-benefitting trait after the transfer to another B. subtilis strain lacking the prophage previously. Phages of the SPβgroup like phi3T use a peptide-based communication system (termed the “arbitrium” system) to coordinate lysis-lysogeny decisions. In the early stage of infection, the number of phages and the peptide concentration is low and a transcription antiterminator protein allows the synthesis of an antitoxin. Consequently, lytic transcripts are not degraded and SPβ remains in the lytic cycle. With increasing peptide concentrations, the peptide enters the cell and inactivates the transcription antiterminator protein. The lytic transcripts are degraded, and the phages enters the lysogenic state. Recently, we have identified the master repressor of SPβ and a factor that acts downstream of the repressor and is critical for the activation of the lytic cycle. Although many additional components of the lysis-lysogeny decision system have already been identified, it is unclear how the lysogenic cycle, particularly in the case of the phage SPβ, is activated. The current status of the project is presented.

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