Streptomyces
Over the last century, Streptomyces bacteria – and their metabolic products – have revolutionized modern medicine. These little pharmaceutical factories produce a vast array of natural products that have been co-opted for medical and agricultural therapies. In addition to their metabolic sophistication, Streptomyces also exhibit remarkable developmental and regulatory complexity.
Guest-edited by Dr Marie Elliot, this collection of keynote research articles will highlight fascinating aspects of Streptomyces biology, and the advances that are providing us with newfound insight and appreciation for these extraordinary bacteria.
Collection Contents
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Comparative biochemical and structural analysis of the flavin-binding dodecins from Streptomyces davaonensis and Streptomyces coelicolor reveals striking differences with regard to multimerization
Dodecins are small flavin-binding proteins that are widespread amongst haloarchaeal and bacterial species. Haloarchaeal dodecins predominantly bind riboflavin, while bacterial dodecins have been reported to bind riboflavin-5′-phosphate, also called flavin mononucleotide (FMN), and the FMN derivative, flavin adenine dinucleotide (FAD). Dodecins form dodecameric complexes and represent buffer systems for cytoplasmic flavins. In this study, dodecins of the bacteria Streptomyces davaonensis (SdDod) and Streptomyces coelicolor (ScDod) were investigated. Both dodecins showed an unprecedented low affinity for riboflavin, FMN and FAD when compared to other bacterial dodecins. Significant binding of FMN and FAD occurred at relatively low temperatures and under acidic conditions. X-ray diffraction analyses of SdDod and ScDod revealed that the structures of both Streptomyces dodecins are highly similar, which explains their similar binding properties for FMN and FAD. In contrast, SdDod and ScDod showed very different properties with regard to the stability of their dodecameric complexes. Site-directed mutagenesis experiments revealed that a specific salt bridge (D10–K62) is responsible for this difference in stability.
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Characterization of the small flavin-binding dodecin in the roseoflavin producer Streptomyces davawensis
Genes encoding dodecin proteins are present in almost 20 % of archaeal and in more than 50 % of bacterial genomes. Archaeal dodecins bind riboflavin (vitamin B2), are thought to play a role in flavin homeostasis and possibly also help to protect cells from radical or oxygenic stress. Bacterial dodecins were found to bind riboflavin-5′-phosphate (also called flavin mononucleotide or FMN) and coenzyme A, but their physiological function remained unknown. In this study, we set out to investigate the relevance of dodecins for flavin metabolism and oxidative stress management in the phylogenetically related bacteria Streptomyces coelicolor and Streptomyces davawensis. Additionally, we explored the role of dodecins with regard to resistance against the antibiotic roseoflavin, a riboflavin analogue produced by S. davawensis. Our results show that the dodecin of S. davawensis predominantly binds FMN and is neither involved in roseoflavin biosynthesis nor in roseoflavin resistance. In contrast to S. davawensis, growth of S. coelicolor was not reduced in the presence of plumbagin, a compound, which induces oxidative stress. Plumbagin treatment stimulated expression of the dodecin gene in S. davawensis but not in S. coelicolor. Deletion of the dodecin gene in S. davawensis generated a recombinant strain which, in contrast to the wild-type, was fully resistant to plumbagin. Subsequent metabolome analyses revealed that the S. davawensis dodecin deletion strain exhibited a very different stress response when compared to the wild-type indicating that dodecins broadly affect cellular physiology.
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A Conditional Aerial Mycelium-Negative Mutant Of Streptomyces Fradiae with Deficient Ornithine Carbamoyltransferase Activity
More LessA mutant defective in ornithine carbamoyltransferase activity and having a concomitant aerial mycelium-negative phenotype was isolated from Streptomyces fradiae. The aerial mycelium formation of the mutant could be restored by replacing l-arginine with l-citrulline in the minimal medium. The possibility that the ornithine cycle is connected with the regulation of aerial mycelium formation is discussed.
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Characterization of Ca2+-ATPase Activity in Streptomyces griseus
More LessSUMMARY: Ca2+-ATPase activity has been characterized in Streptomyces griseus. The enzyme has a pH optimum of 8·5 at 37°C. Its Ca2+ requirement can be substituted by Cd2+, Zn2+ and Mn2+. Mg2+ inhibits the enzyme non-competitively.
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