Plant biologists at The University of Western Australia have discovered that the commonly used antibiotic ciprofloxacin, which kills bacteria, also kills plants by blocking the DNA copying machinery of the plants.

The research, which was published today in The Journal of Biological Chemistry, was a collaboration between UWA researchers and Professor Tony Maxwell from the John Innes Centre in the UK.

The work at UWA was carried out by graduate research assistant Julie Leroux and Dr Joshua Mylne, a Future Fellow in UWA’s School of Chemistry & Biochemistry and affiliated to the ARC Centre of Excellence in Plant Energy Biology.

Dr Mylne said the researchers found a plant that could grow on ciprofloxacin and by working out which gene mutation enabled this, could prove how the antibiotic killed plants.

“This could be the starting point for making a completely new herbicide,” he said.

“The DNA copying machinery in plants and microbes have similarities, but also differences that could be exploited.

“The machinery that ciprofloxacin affects is not currently targeted by known herbicides, making this an untried mode of action to focus on.”

Dr Mylne said the UWA research team’s contribution was to provide the plant proof that the mutated gene was responsible for its ability to grow on ciprofloxacin.

This work built on prior knowledge from Professor Maxwell’s lab that the enzyme DNA gyrase (part of the DNA copying machinery) is made in plants and is essential in plant growth and development.

By generating mutations in the model plant Arabidopsis thaliana and finding one plant that is resistant to the antibiotic ciprofloxacin and analysing its genome, the team confirmed that DNA gyrase in plants can be targeted effectively by this antibiotic.

“We envision changing ciprofloxacin in ways that will stop it from being an antibiotic, while improving its suitability as a herbicide,” Dr Mylne said.