Investigating the effect of the antibiotic tunicamycin on wall teichoic acid synthesis and toxicity in Staphylococcus aureus.

Student thesis: Master's ThesisMaster of Science by Research (MScR)

Abstract

Staphylococcus aureus toxins, expressed under control of the accessory gene regulator (Agr) quorum-sensing system, are crucial virulence factors that facilitate the progression of infection. Recently, wall teichoic acid (WTA), a cell wall glycopolymer covalently linked to peptidoglycan (PG) has been associated with optimal toxicity. TarO is the first enzyme in the WTA synthesis pathway, which comprises a series of enzyme-catalysed steps, followed by translocation across the membrane via the TarGH transporter and attachment to PG. The antibiotic tunicamycin has previously been used to inhibit WTA synthesis in S. aureus, as it inhibits the TarO enzyme. This project aimed to use subinhibitory concentrations of tunicamycin to inhibit WTA synthesis in four S. aureus strains, to identify whether a reduction in WTA content results in decreased toxicity, due to inhibition of toxin release. As we needed to separate the effect of Agr-related toxin regulation from the effect of WTA on toxin release, we first needed to identify subinhibitory tunicamycin concentrations with no inhibiting effect on Agr. WTA was then extracted to confirm a reduction in WTA content upon exposure to these concentrations of tunicamycin. THP-1 toxicity assays were used to investigate the effect of tunicamycin on toxicity, and SDS-PAGE gels used to investigate localisation of the phenol soluble modulin toxins, to confirm whether toxin release is inhibited by tunicamycin. Results showed a significant reduction in toxicity upon exposure to subinhibitory tunicamycin concentrations in 2 of the 4 strains at all tunicamycin concentrations tested and in a third strain at the highest concentration tested, due to inhibition of toxin release. This confirms the involvement of WTA in toxin secretion and suggests that exposure to subinhibitory tunicamycin concentrations may attenuate virulence. This reveals the potential for the use of tunicamycin at subinhibitory concentrations as an anti-virulence therapeutic to reduce S. aureus infection severity.
Date of Award24 Jan 2023
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorRuth C Massey (Supervisor)

Cite this

'