Shigatoxin encoding Bacteriophage \u03d524B modulates bacterial metabolism to raise antimicrobial tolerance

G S Holt,H E Allison,A Sails,A K Brown,A K Graham,D L Smith,C V Lanyon,S H Bridge,G Young,A J Mccarthy,M Veses-Garcia,J K Lodge

doi:10.1038/srep40424

Abstract

How temperate bacteriophages play a role in microbial infection and disease progression is not fully understood. They do this in part by carrying genes that promote positive evolutionary selection for the lysogen. Using Biolog phenotype microarrays and comparative metabolite profiling we demonstrate the impact of the well-characterised Shiga toxin-prophage ϕ24B on its Escherichia coli host MC1061. As a lysogen, the prophage alters the bacterial physiology by increasing the rates of respiration and cell proliferation. This is the first reported study detailing phage-mediated control of the E. coli biotin and fatty acid synthesis that is rate limiting to cell growth. Through ϕ24B conversion the lysogen also gains increased antimicrobial tolerance to chloroxylenol and 8-hydroxyquinoline. Distinct metabolite profiles discriminate between MC1061 and the ϕ24B lysogen in standard culture, and when treated with 2 antimicrobials. This is also the first reported use of metabolite profiling to characterise the physiological impact of lysogeny under antimicrobial pressure. We propose that temperate phages do not need to carry antimicrobial resistance genes to play a significant role in tolerance to antimicrobials.

Highlights

Colonisation by Shiga toxin-encoding Escherichia coli (STEC) causes a potentially fatal gastrointestinal infection in humans
This interaction is conserved in Shiga toxin (Stx)-phages as the incidence of the tail and host recognition protein is widespread21. φ2 4B has been shown to survive well in compost models[22], and infectivity after 30 days in bovine manure and slurry23. φ24B is genetically similar to phages isolated from sporadic outbreaks of STEC with high virulence and a good model of the viruses circulating in E. coli populations in the environment[13]
In this study we focus on phage mediated antimicrobial tolerance to antibiotics found in the livestock farm setting which is the primary reservoir of pathogenic shigatoxigenic E. coli

Summary

Discussion

The accessory genome of bacteria promoted through horizontal gene transfer is important in understanding how mobile genetic elements aid selection in the environment. Ophthalmic acid intensity mirrored the stationary phase levels of FAPy-adenine, across all tests, it was present in standard culture conditions in both the early and mid-exponential growth phase cultures This observation from our metabolomic analysis implies higher oxidative stress in the lysogen at stationary growth, as the data is supported by Desnues et al.[82]. 8-hydroxyquinoline treatment drives early cellular stress, cell death and lysis which increases extracellular lipids that bind free drug, allowing the community to continue to grow The mechanism for this is unclear, yet this is importantly linked to subversion of the bacterial cell because no phage encoded metabolites are present. We propose that temperate phages may not carry ARGs but play a larger role interfering with metabolic regulation that alters bacterial sensitivity to antimicrobials

Materials and Methods

Author Contributions

Findings

Additional Information