| Streptomyces are an important group of soil microorganisms that produce variety of secondary metabolites. This dissertation involves research on characterization of novel members of the Streptomyces violaceusniger clade and characterization of antibiotic sysnthesis genes from Streptomyces lydicus WYEC 108.;Two strong antifungal antibiotic producing isolates, 1UA-1 and 5US-2, were isolated from sugar beet field soil samples and characterized as typical Streptomyces based on their chemical and morphological properties. From the results of physiological, morphological and genetic characterizations, we determined that these two Streptomyces isolates while very similar to each other are distinct in genetic and phenotypic properties from type culture strains Streptomyces tubercidicus DSM 40261. Both 1UA-1 and 5US-2 can be considered as distinct strain of S. tubercidicus , and both are potential sources of useful antifungal antibiotics, not produced by the type cultures.;Streptomyces strains were isolated from a sagebrush rhizosphere soil sample on humic acid vitamin (HV) agar and water yeast extract (WYE) agar supplemented with 1.5% (w/w) of phenol as a selective medium, since a recent publication found members of the Streptomyces violaceusniger clade to be especially resistant to phenol. The isolates showing broad spectrum antifungal and anti-yeast activity were all members of the clade. We conclude that screening of isolates for broad spectrum antifungal/anti-yeast activity is the preferred method for isolation of S. violaceusniger clade strains, rather than biocide-based selection.;Streptonryces lydicus WYEC 108, an actinomycete isolated from the rhizosphere of linseed plants, produces multiple antifungal antibiotics including compounds active against fungi resistant to commercially used antifungal antibiotics. Using two PCR products, we successfully amplified the KS alpha and dNDP-glucose dehydratase gene and constructed fosmid library. Double positive clone, B5D5, was further analyzed and showed to encode red pigment antibiotic synthesis regulatory genes. |
