Bacteriophages, viruses of bacteria, are the most abundant life form on Earth. The prospect of using them in the fight against pathogenic bacteria has long been recognised, but their high specificity and unpredictable reproduction limits their use in medicine. The mechanisms phages use to fight bacteria are attractive candidates for the development of novel antimicrobial applications as they are more general, but are still very poorly understood. Indirect evidence exists of toxin antitoxin systems (TAS) and stringent response involvement in phage defense. Stringent response is a stress response of bacteria that reprograms them from growth (when they are sensitive to different antimicrobial applications) to stress survival (when bacteria are highly tolerant). Although the constant co-evolution of phages and bacteria suggests that phages have a way of overcoming all of the wide variety of bacterial defense systems, yet, no direct phage mechanisms targeting bacterial stringent response have been identified.
We hypothesize that as the bacterial toxin-antitoxin systems and stringent response play a part in the arms race between bacteria and phages, we can provide direct molecular evidence and identify phage proteins involved in these interactions. We will create and characterise, morphologically and molecularly, a novel library of phages infecting a biotechnologically important bacterium - Pseudomonas putida PaW85, and uncover the stringent response- and TAS-mediated phenotypic effects and their molecular mechanisms on P. putida phage tolerance. By functionally and structurally characterizing the anti-stringent response phage effectors, we will bridge several gaps in the phage-bacteria interaction research. By knowing better the phage defense determinants of P. putida, we will advance the phage research of this biosynthesis and biodegradation strain. We will also provide crucial basic knowledge that can lead to the development of novel, efficient phage therapy solutions that directly target bacterial stress-mechanisms.
