Dana Schneider (Tübingen / DE), Annika Esch (Tübingen / DE), Alena Strüder (Tübingen / DE), Evi Stegmann (Tübingen / DE), Chambers C. Hughes (Tübingen / DE), Heike Brötz-Oesterhelt (Tübingen / DE)
An obstacle during natural product screening is the rediscovery of known compounds. To increase chemical diversity, producer species can be cultivated under different growth conditions. Induction of silent biosynthetic gene clusters allows access to new, or underexplored, agents. We identified a new producer of the underexplored isonitrile compound hazimycin. For hazimycin, antibiotic activity against Gram-positive and Gram-negative bacteria was described1,2 but mode of action information was lacking. In the last decades, naturally occurring diisonitrile compounds were discovered from fungi, bacteria, and sponges, but only a few of them were investigated for their mode of action3. To increase knowledge on the effects of diisonitrile compounds, we studied the mode of action of hazimycin.
Hazimycin inhibited the growth of Bacillus subtilis and Escherichia coli but did not prevent growth completely. Derivatives confirmed that the isonitrile moiety is essential for bioactivity. Copper binding could be proven for hazimycin, in accordance with the mechanism of other isonitriles4, and binding constant and stoichiometry were determined by isothermal titration calorimetry. The impact of hazimycin on B. subtilis was profiled by fluorescence microscopy and the production of reactive oxygen species (ROS) and ATP levels were analyzed. The mechanism of action of hazimycin appears pleiotropic involving ROS and potential impairment of the respiratory chain.
1Marquez, J. A. et al. The hazimicins, a new class of antibiotics. Taxonomy, fermentation, isolation, characterization and biological properties. J Antibiot (Tokyo) 36, 1101-1108 (1983).
2Wright, J. J. K. et al. X-Ray crystal structure determination and synthesis of the new isonitrile-containing antibiotics, hazimycin factors 5 and 6. Journal of the Chemical Society, Chemical Communications, 1188-1190 (1982).
3Zhu, M. et al. Diisonitrile-Mediated Reactive Oxygen Species Accumulation Leads to Bacterial Growth Inhibition. J Nat Prod 83, 1634-1640 (2020)
4Massarotti, A., Brunelli, F., Aprile, S., Giustiniano, M. & Tron, G. C. Medicinal Chemistry of Isocyanides. Chem Rev 121, 10742-10788 (2021)