Genetic regulation and biological function of the novel antimicrobial target gene samA in Pseudomonas aeruginosa
Publication Date
December 13, 2023
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen causing life-threatening infections due to the array of virulence factors it produces, in addition to being a multidrug-resistant organism for which conventional antibiotics fail to be adequate for treatment.
Therefore, the challenges posed by the global issue of drug-resistant bacterial infections call on the development of new strategies to tackle those infections. Non-biocidal approaches, that aim at ‘disarming’ the pathogens from virulence are in the spotlight.
The gene of interest investigated in this study, samA was uncovered by an integrated whole genome screening using several disease models as a promising antimicrobial target gene.
Hence, one aim of this PhD project, reported in Chapter 3 was to advance the knowledge of the samA gene’s impact on the growth and production of virulence traits in P. aeruginosa, among others. The most striking finding was the twitching impairment in the samA gene deletion mutant and a possible role of samA in P. aeruginosa surface attachment.
Interestingly, samA is located upstream of a unique tRNA gene in P. aeruginosa, which is predicted to incorporate a unique aminoacid in proteins via a dedicated codon system. It was hypothesised that SamA might be acting as a methyltransferase adding a modification on this tRNA, ultimately aiding adaptation to anaerobiosis through a mechanism similar to the one described in E. coli.
Chapter 4 primarily sought to analyse SamA bioinformatically and, secondly, to assess the catalytic activity of SamA in P. aeruginosa. The main finding from this chapter was that the predicted secondary structure of SamA indicates that it could be a putative tRNA methyltransferase, though further work remains to be done in this direction.
Since it was hypothesized that SamA modifies this unique tRNA, Chapter 5 reports the in silico analysis of this unique tRNA and the unique modified protein sequences from P. aeruginosa to assess their potential in roles equivalent to those described in E. coli. Overall, the findings from the bioinformatic analysis supported this hypothesis, which constitutes a starting point for future work on the elucidation of these mechanisms in P. aeruginosa.
To get a broader view of the functions and unravel the roles of SamA and this tRNA’s in P. aeruginosa, Chapter 6 sought to use transcriptomics. The results indicate that samA has a greater effect under anaerobic compared to aerobic conditions, which suggests a more important role for SamA under those conditions. This is in line with the hypothesis that SamA plays a role in P. aeruginosa adaptation to anaerobic growth.
However, the most striking finding was that in the tRNA-deficient mutant the equivalents of two homologous genes involved in this decoding mechanism in E.coli were found downregulated.
All in all, this study paved the way towards the elucidation of the roles played by SamA and the unique tRNA in the lifestyle of P. aeruginosa. The results obtained have also suggested a possible involvement of these uniquely modified proteins in the virulence of P. aeruginosa. These findings have therefore highlighted the importance of further characterising these proteins since they may be exploited as potential targets for preventing P. aeruginosa infections.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
School of Life Sciences
eprints ID
73529
UoN Repository URI
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