title: Production of fungal and bacterial growth modulating secondary metabolites is widespread among mycorrhiza-associated streptomycetes.
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.
authors.affiliation: IMIT-Physiological Ecology of Plants, Auf der Morgenstelle 1, 72076, Tuebingen, Germany.
authors.forename: Silvia D
authors.initials: SD
authors.lastname: Schrey
authors.forename: Eric
authors.initials: E
authors.lastname: Erkenbrack
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Früh
authors.forename: Svenja
authors.initials: S
authors.lastname: Fengler
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hommel
authors.forename: Nadine
authors.initials: N
authors.lastname: Horlacher
authors.forename: Dirk
authors.initials: D
authors.lastname: Schulz
authors.forename: Margret
authors.initials: M
authors.lastname: Ecke
authors.forename: Andreas
authors.initials: A
authors.lastname: Kulik
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Fiedler
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Hampp
authors.forename: Mika T
authors.initials: MT
authors.lastname: Tarkka
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism*; D000935:Antifungal Agents / Q000378:metabolism*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D056265:Microbial Interactions; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000187:drug effects* / Q000254:growth & development*; D010802:Phylogeny; D028222:Picea / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013302:Streptomyces / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D036341:Intercellular Signaling Peptides and Proteins; D012336:RNA, Ribosomal, 16S