Emilie Søndberg:
Molecular Mechanisms Underlying Uptake, Maintenance and Release of Foreign DNA in Escherichia coli and Vibrio anguillarum

Genomic plasticity and the horizontal transfer of genomic material between bacteria have time again been highlighted as one of the most important forces of evolution. It has the potential of shaping new pathogens, increasing virulence of the existing and spreading antibiotic resistance. Central in the processes underlying the uptake, maintenance and release of foreign DNA is important transcription factors whose large regulons shapes the molecular mechanisms taking place in the cell. 
In several Gram-negative pathogens natural competence, the ability to take up free environmental DNA and incorporating this into the native chromosome, is regulated by the concerted action of cAMP Receptor Protein (CRP) and the transcriptional co-regulator Sxy. 

I present new insights into how the classically studied and highly conserved transcriptional regulator CRP interacts directly with co-regulator Sxy to regulate a specialized subset of promoters preceding genes forming the supposed competence regulon of E. coli. 

Quorum sensing (QS) used by many pathogenic bacteria to coordinate group behavior relies on the secretion and detection of signal molecules. The transcription factor VanT acts as the master QS regulator and remodels gene expression in Vibrio anguillarum causing dramatic changes in phenotype and virulence. Recently QS has emerged as an important regulator of phage-host interactions. Bacteriophages, small viruses that infects bacteria, can follow a path in their development upon entry into a new host that leads to the death of the bacterium and an explosion of progeny. 

Alternatively phages can exist as a part of the inherited bacterial genome, creating an opportunity for intimate co-development for the mutual benefit of both. Phages can be used to fight detrimental bacteria, yet as transfer of genomic material between their hosts can be a consequence of all phage lifestyles it is important to understand the mechanisms at play.

We investigate how QS stimulates induction of the widely spread prophage p41 and find that this involves direct repression of a phage-encoded transcription factor by VanT. The VanT regulon of two wild type isolates is here characterized to increase our understanding of how this important fish pathogen remodels gene expression.