Editorial – preview

Streptomycetes are the main source for a huge repertoire of small molecules, which are in use as antibiotics, anti-fungals, antiparasitics, or as antitumor and immunosup-pressive drugs. As outlined in minireviews and original articles within this special issue, cloning, designed mutations , the comparisons of transcripts, proteomes and metabolites have provided considerable insights into the biosynthesis of metabolites, and the characterization of global and specific regulators, and carbon fluxes. These and future studies will be the basis of systems biology for streptomycetes. The availability of genome sequence information from Streptomyces species facilitates the discovery of an additional large gene pool of clusters for cryptic secondary metabolites and for orphan proteins of unknown functions. An increasing number of investigations have provided novel insights into extracellular protein complexes, signalling and interactions. To manipulate streptomycetes for an increasing number of applications , it will be important that researchers elucidate many more complex biological aspects, under laboratory and environmental conditions. In the following, we summarize the main results and implications of the research presented within the articles of this special issue. The results of numerous studies have provided an emerging picture of control mechanisms for primary and secondary metabolism in streptomycetes. Within their minireview, Martín and colleagues (2011) present an integrated view on current knowledge about interactions between the global nutritional regulators PhoP, GlnR, DasR and AfsR, and other poorly known nutritional regulators in the model species Streptomyces coelicolor A3(2). From the diversity of Streptomyces species, reflected in differences between the respective genomes, they infer species-specific interactions between these global regulators. They conclude that a deeper understanding of molecular interactions and the integration of signals is an essential basis for ongoing systems biology investigations into the complexity of regulatory networks. Important signals in this context are the g-butyrolactones. In S. coelicolor, the g-butyrolactone syn-thase ScbA is responsible for the biosynthesis of signalling molecules called SCBs (S. coelicolor butanolides). D'Alia and colleagues (2011) showed by transcriptome analysis that the scbA mutant had a strong perturbation in the expression of gene clusters for three pigmented antibiotics , and that the synthesis of the siderophore desfer-rioxamine is also under SCB control. The expression of some genes for the primary metabolism occurred earlier in the mutant, indicating mutual control of both primary and secondary metabolism. Siderophore-mediated iron acquisition has received increased attention. The siderophore-binding receptor DesE is abundant among streptomycetes, while the CdtB counterpart is only found in certain …