On 19th of August at 12:15 Jelena Beljantseva will defend her doctoral thesis „Small fine-tuners of the bacterial stringent response – a glimpse into the working principles of Small Alarmone Synthetases"
Supervisors: senoir researcher Vasili Hauryliuk, professor Tanel Tenson (University of Tartu, Institute of Technology)
Opponent: professor Kaspars Tārs, University of Latvia (Universitas Latviensis), Latvia
Bacteria, being the most abundant organisms in the world, live and survive in the most extreme and unreachable places of our planet. They are able to withstand such conditions as extreme cold or heat, excessive salinity, lack of oxygen etc. Moreover, for pathogenic bacteria, immune system of the host organism is also a challenge to put up with.
In order to combat hostile and continuosly changing conditions bacteria have evolved regulatory mechanisms to sense the environmental cues and change their physiology in response. One of the most global such mechanism is the stringent response. This process is mediated by the alarmone molecule named (p)ppGpp which is synthesized in bacterial cell in response to nutrient, heat and other stresses. Accumulation of this molecule leads to reprogramming of bacterial physiology such that growth and division are repressed and survival mechanisms are upregulated. This leads to increased viability of bacterium in adverse conditions. Stringent response is also implicated in virulence, antibacterial resistance and biofilm formation, therefore making this process an important study subject from the clinical point of view.
(p)ppGpp levels are regulated by the representatives of RelA-SpoT Homolog (RSH) family of proteins. These enzymes are highly conserved among bacteria due to their evolutionary importance and the universal nature of the stringent response in bacteria. In this thesis, I contribute to knowledge on RSH enzymes by taking a glimpse into working mechanisms of Small Alarmone Synthetases (SAS) – so far not so well studied RSH representatives. Specifically, I have investigated the enzymatic characteristics of two SAS: Enterococcus faecalis RelQ and Staphylococcus aureus RelP. The distinctive features of the working principles found for these proteins underlay their role in fine-tuning the stringent response.