Martina Bianchi (Tübingen / DE), Marina Borisova-Mayer (Tübingen / DE), Theresa Harbig (Tübingen / DE), Johanna Rapp (Tübingen / DE), Jan Bornikoel (Tübingen / DE), Kay Nieselt (Tübingen / DE), Hannes Link (Tübingen / DE), Heike Brötz-Oesterhelt (Tübingen / DE), Christoph Mayer (Tübingen / DE)
Introduction:
Antimicrobial resistance worsens every year due to the growing gap between MDR bacteria proliferation and the slow rate of new antibiotics" discovery. However, many old antimicrobial drugs, like fosfomycin (FOS) first discovered in 1969, are still active against MDR pathogens. FOS blocks the MurA enzyme, and this unique mechanism of action makes it ideal for combinatorial therapies. Despite routine FOS prescription for urinary tract infections caused by Escherichia coli, relapse rates remain high. FOS-treated E. coli rapidly develops resistance to FOS through genetic mutations, but little is known about possible metabolic adaptations that also enable its survival. Moreover, it is still obscure how FOS globally impacts the cell, to carry on its bactericidal effect.
Goal:
Investigate FOS effects on E. coli, beyond its action on MurA, and elucidate metabolic pathways crucial for the drug bactericidal effect or for bacterial survival.
Material and methods:
Experiments were performed on E. coli BW25113 and on KO-mutants of the genes of interest. We obtained omics data of FOS-treated E. coli through Illumina RNA Sequencing and time-resolved metabolomics (HPLC-MS). Time-lapse microscopy of FOS-treated cells showed morphological alterations that allow bacterial survival. The evaluation of the metabolic pathways of interest was performed through antibiotic susceptibility testing.
Results:
We showed that E. coli BW25113 responds to FOS by deep alterations of its metabolomic and transcriptional state. Moreover, treated bacteria transform into L-form like spheroplasts, survive for a long time in such state and eventually revert to a bacillar form and grow exponentially again. We then focused our investigation particularly on a CreBC-related response and evaluated its role in the bacterial response to the drug.
Summary:
FOS is still active against MDR bacteria, but how it globally affects the cells is still not understood, even if the antimicrobial mode of action should be investigated beyond the drug-target mere interaction. We showed global alterations in FOS-treated E. coli and further studied the role of a FOS-induced CreBC-related response.