The least inhibited fungus in these bioassays was Piloderma croceum, closely related to the mycorrhizal fungus Piloderma sp., the fungus which dominated in the Norway spruce mycorrhizal roots used for isolations. This suggests the potential of such a niche-related community for protecting Norway spruce-Piloderma mycorrhizas from fungal and bacterial parasites without incurring harm to the host fungus. The production of secondary
metabolites by mycorrhiza associated streptomycetes After many years of intensive screening of actinomycetes, the frequency of discovering structurally new compounds is apparently decreasing . Since the current strategies for addressing SYN-117 ic50 the urgent need for new
antibiotics are not efficient enough, another approach might be to examine new niches, or sources, for microbial resources that produce novel compounds . To search for compounds that affect fungal growth we performed HPLC analyses coupled with UV/Vis detection and mass spectrometry with five selected mycorrhiza-associated streptomycetes, possessing different activities in Streptomyces-fungus bioassays. Typically, only a mTOR inhibitor limited number of metabolites are produced Tanespimycin manufacturer in synthetic media , and to promote production of diverse metabolites two different culture media were employed. The five strains produced diffusible secondary metabolites, of which only seven could be identified using the HPLC-UV–vis database containing 960 reference compounds , NIST database, and MS analyses. The identified metabolites included antifungal and antimicrobial substances as well as siderophores. The fungal inhibitory strain Streptomyces AcM11 produced the most characterized metabolites, the antibiotics Acta 2930 B1, actiphenol, cycloheximide and the siderophore ferulic acid. This indicates that function based screening, e.g. selection of isolates that are highly inhibitory towards fungi for biocontrol applications, may create a bias towards strains producing 3-mercaptopyruvate sulfurtransferase known
compounds. Based on spectral measurements and MS analyses, a total of twenty one compounds were produced by the five isolates, suggesting an abundance of yet unreported, putatively bioactive compounds. Nevertheless, at least 7000 secondary metabolites have been discovered from streptomycetes , and the genome sequences of Streptomyces spp. commonly contain 20-30 gene clusters for secondary metabolite synthesis, of which approximately 30% may encode biochemical pathways for antibiotics production . Thus, to conclusively determine the novelty of such substances both structural and chemical elucidation as well as the use of comprehensive substance databases is indispensable.