Oral Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

Determining the molecular effects of 5-fluorocytosine on the pathogenicity of Pseudomonas aeruginosa (732)

Jessica M Thomson 1 , Iain L Lamont 1
  1. University of Otago, Dunedin, OTAGO, New Zealand


Pseudomonas aeruginosa is an opportunistic pathogen responsible for a variety of infections. Like many pathogenic bacteria, P. aeruginosa presents a challenge to conventional antibiotic therapeutics because of the evolution of resistance.  One approach to antibiotic discovery is to screen drugs approved for other purposes for antibiotic activity. Identified compounds can potentially be repurposed and fast-tracked into clinical use. This approach has identified the antimycotic drug 5-fluorocytosine as reducing pathogenicity of P. aeruginosa in a murine infection model. The aim of the presented research is to determine how 5-fluorocytosine reduces pathogenicity of P. aeruginosa.


RNAseq and proteomics were used to identify genes and proteins whose expression is affected by 5-fluorocytosine.


After 4 h of treatment, over 300 genes involved in a variety of different functions and pathways were found to be differentially expressed using RNAseq. A large portion of the genes were pathogenicity-related. In particular, 5-fluorocytosine strongly increased the expression of genes required for the production of pyocyanin. Pyocyanin is implicated in facilitating redox balance in P. aeruginosa. A proteomics approach also identified proteins involved in pyocyanin synthesis as upregulated in 5-fluorocytosine treated bacteria.


RNAseq showed that 5-fluorocytosine treatment had a broad effect on P. aeruginosa gene expression, likely explaining why this compound reduces pathogenicity. This information on differentially expressed genes is currently being used to help determine the mechanism of action of 5-fluorocytosine on P. aeruginosa.