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This study focused on the involvement of theunusual nucleotide (p)ppGpp, a stringent factor, during theStreptomycescoelicolor. Two genes, relA and rshA, were disrupted todemonstrate the roles of the stringent factor in the diferentiation.The intracelular concentration of (p)ppGpp in the wild-type(M600) and disrupted mutants was measured in relation to theintentional starvation of a specific nutrient, such as carbon,nitrogen, and phosphate or the in situ depletion of nutrients in abatch culture. As a result, it was found that the morphologicalcharacteristic of the relA mutant was a bld phenotypeforming condensed mycelia, whereas the rshA mutant grewfast-forming spores and straightforward mycelia. In bothmutants, the production of actinorhodin (Act) was completelyabolished, yet the undecylprodigiosin (Red) production wasincreased. Intracellular (p)ppGp was detected in the relAmutant in the case of limited phosphate, yet not with limitedcarbon or nitrogen sources. In contrast, (p)ppGpp was producedin the rshA mutant under limited carbon and nitrogenS. coelicolor was found tobe selectively regulated by either the RelA or RshA protein,which was diferentially expressed in response to the specificnutrient limitation. These results were also supported by thein situ ppGpp production during a batch culture. Furthermore,it is suggested that RelA and RshA are bifunctional proteinsthat posess the ability to both synthesize and hydrolyze(p)ppGpp.