Arousing sleeping genes: shifts in secondary metabolism of metal tolerant actinobacteria under conditions of heavy metal stress |
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Authors: | Götz Haferburg Ingrid Groth Ute Möllmann Erika Kothe Isabel Sattler |
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Institution: | 1. Institute of Microbiology, Friedrich-Schiller University Jena, Neugasse 25, 07743, Jena, Germany 2. Leibniz Institute for Natural Product Research and Infection Biology e.V./Hans-Kn?ll-Institute (HKI), Beutenbergstr. 11a, 07745, Jena, Germany
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Abstract: | Numerous microbial habitats are strongly influenced by elevated levels of heavy metals. This type of habitat has developed
either due to ore mining and metal processing or by pedogenesis above metal-rich base rocks. Most actinobacteria are soil-borne
microbes with a remarkable capability for the synthesis of a broad variety of biologically active secondary metabolites. One
major obstacle in identifying secondary metabolites, however, is the known phenomenon of sleeping gene clusters which are
present, but silent under standard screening conditions. Here, we proceed to show that sleeping gene clusters can be awakened
by the induction in heavy metal stress. Both, a chemical and a biological screening with extracts of supernatant and biomass
of 10 strains derived from metal contaminated and non-contaminated environments was carried out to assay the influence of
heavy metals on secondary metabolite patterns of metal tolerant actinobacteria. Metabolite patterns of cultures grown in complex
and minimal media were compared to nickel (or cadmium) spiked parallels. Extracts of some strains grown in the presence of
a metal salt displayed intense antibiosis against Escherichia coli, Mycobacterium smegmatis, Staphylococcus aureus and Candida albicans. Contrarily to the widely held opinion of metals as hindrance in secondary metabolism, metals thus can induce or enhance
synthesis of possibly potent and medically relevant metabolites in metal tolerant strains. Hence, re-screening of existing
strain libraries as well as identification of new strains from contaminated areas are valid strategies for the detection of
new antibiotics in the future. |
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Keywords: | Actinobacteria Antibiosis Heavy metal Screening program Secondary metabolism |
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