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Annice Hemmerling
The newly discovered natural product group of keanumycins in bacteria works effectively against the plant pest Botrytis cinerea, which triggers grey mould rot and causes immense harvest losses every year. But the active ingredient also inhibits fungi that are dangerous to humans, such as Candida albicans. According to previous studies, it is harmless to plant and human cells.
The fact that the researchers have now found a new active ingredient in bacteria of the genus Pseudomonas is no coincidence. "We have been working with pseudomonads for some time and know that many of these bacterial species are very toxic to amoebae, which feed on bacteria," says study leader Pierre Stallforth. He is the head of the department of Paleobiotechnology at Leibniz-HKI and professor of Bioorganic Chemistry and Paleobiotechnology at Friedrich Schiller University in Jena. It appears that several toxins are responsible for the deadly effect of the bacteria, of which only one was known so far. In the genome of the bacteria, the researchers have now found biosynthesis genes for the newly discovered natural products, the keanumycins A, B and C. This group of natural products belongs to the nonribosomal lipopeptides with soap-like properties.
Together with colleagues at the Bio Pilot Plant of the Leibniz-HKI, the researchers succeeded in isolating one of the keanumycins and conducting further tests. "The lipopeptides kill so efficiently that we named them after Keanu Reeves because he, too, is extremely deadly in his roles," Götze explains with a wink.
The researchers suspected that keanumycins could also kill fungi, as these resemble amoebas in certain characteristics. This assumption was confirmed together with the Research Centre for Horticultural Crops at the University of Applied Sciences Erfurt. There, Keanumycin was shownto be effective against grey mould rot on hydrangea leaves. In this case, culture fluid that no longer contained bacterial cells was sufficient to significantly inhibit the growth of the fungus.
"Theoretically, the keanumycin-containing supernatant from Pseudomonas cultures could be used directly for plants," says Götze. Further testing will be carried out together with the colleagues in Erfurt. Keanumycin is biodegradable, so no permanent residues should form in the soil. This means that the natural product has the potential to become an environmentally friendly alternative to chemical pesticides.
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