Doctoral defence: Tetiana Brodiazhenko “RelA-SpoT homolog enzymes as effectors of Toxin-Antitoxin systems”

On 23 November at 14:15 Tetiana Brodiazhenko will defend her doctoral thesis “RelA-SpoT homolog enzymes as effectors of Toxin-Antitoxin systems”.

Supervisors:
Professor Tanel Tenson, University of Tartu
Associate Professor Vasili Hauryliuk, University of Tartu

Opponent:
Professor Tim R. Blower, Durham University (United Kingdom)

Summary
Like all living organisms, bacteria sense the environment and respond to plethora of stresses by adjusting their physiology accordingly. One of the central bacterial stress pathways is the stringent response (SR). The stringent response mediates the bacterial adaptation to nutrient limitation as well as to in response to abiotic environmental stresses like heat shock. More than six decades ago alarmone nucleotides ppGpp and pppGpp – collectively referred to as (p)ppGpp – or the “magic spots” were discovered to be produced in Escherichia coli cells as a response to amino acids limitation. The first physiologial role of the SR to be characterised was inhibition of stable RNA (rRNA and tRNA) synthesis, coordinated with induction of expression of genes involved in amino acid biosynthesis and stress tolerance. However, decades of research have established that in addition to transcription, (p)ppGpp targets multiple other processes in the cell, such as translation, ribosome assembly, metabolism, and impact all the aspects of cell physiology including adaptation to nutrient limitation, antibiotic resistance and virulence. Another regulatory system in bacteria is based on the toxin – antitoxin (TA) systems. First representatives of toxin -antitoxin (TA) systems were discovered in the early 80s. The classical TA systems are bicistronic – i.e. comprised of two gene – operons, in which one gene encodes a protein toxin and the other encodes a protein or RNA antitoxin which neutralises the toxin, either directly or indirectly. Studies of TA systems have exploded in the last years, with numerous new TA families being discovered, their mechanisms of action being characterised, biological functions established and possible applications for biotechnology put forward. The most established functions include plasmid maintenance, defence against bacteriophages and regulation of cell physiology.

Defence can be also followed in Zoom: https://ut-ee.zoom.us/j/3476201026?pwd=TlFQODcrdEZhajBjODI0bm91N2pYQT09 (Meeting ID: 347 620 1026, Passcode: 2021).