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Open Access Highly Accessed Research article

Production of fungal and bacterial growth modulating secondary metabolites is widespread among mycorrhiza-associated streptomycetes

Silvia D Schrey1, Eric Erkenbrack1, Elisabeth Früh1, Svenja Fengler1, Kerstin Hommel3, Nadine Horlacher2, Dirk Schulz2, Margret Ecke1, Andreas Kulik2, Hans-Peter Fiedler2, Rüdiger Hampp1 and Mika T Tarkka13*

Author Affiliations

1 IMIT-Physiological Ecology of Plants, Auf der Morgenstelle 1, 72076, Tuebingen, Germany

2 IMIT-Microbiology/Antibiotics, Auf der Morgenstelle 28, 72076, Tuebingen, Germany

3 Department of Soil Ecology, UFZ-Helmholtz-Centre for Environmental Research, Theodor Lieser Strasse 4, Halle, Germany

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BMC Microbiology 2012, 12:164  doi:10.1186/1471-2180-12-164

Published: 2 August 2012

Abstract

Background

Studies on mycorrhiza associated bacteria suggest that bacterial-fungal interactions play important roles during mycorrhiza formation and affect plant health. We surveyed Streptomyces Actinobacteria, known as antibiotic producers and antagonists of fungi, from Norway spruce mycorrhizas with predominantly Piloderma species as the fungal partner.

Results

Fifteen Streptomyces isolates exhibited substantial variation in inhibition of tested mycorrhizal and plant pathogenic fungi (Amanita muscaria, Fusarium oxysporum, Hebeloma cylindrosporum, Heterobasidion abietinum, Heterobasidion annosum, Laccaria bicolor, Piloderma croceum). The growth of the mycorrhiza-forming fungus Laccaria bicolor was stimulated by some of the streptomycetes, and Piloderma croceum was only moderately affected. Bacteria responded to the streptomycetes differently than the fungi. For instance the strain Streptomyces sp. AcM11, which inhibited most tested fungi, was less inhibitory to bacteria than other tested streptomycetes. The determined patterns of Streptomyces-microbe interactions were associated with distinct patterns of secondary metabolite production. Notably, potentially novel metabolites were produced by strains that were less antagonistic to fungi. Most of the identified metabolites were antibiotics (e.g. cycloheximide, actiphenol) and siderophores (e.g. ferulic acid, desferroxiamines). Plant disease resistance was activated by a single streptomycete strain only.

Conclusions

Mycorrhiza associated streptomycetes appear to have an important role in inhibiting the growth of fungi and bacteria. Additionally, our study indicates that the Streptomyces strains, which are not general antagonists of fungi, may produce still un-described metabolites.