Ochi K
J Gen Microbiol. 1986 Sep;132(9):2621-31. doi: 10.1099/00221287-132-9-2621.
Streptomyces sp. MA406-A-1 produced formycin (a nucleoside antibiotic) in parallel with cell growth in a synthetic medium. When the synthetic medium was supplemented with 1% (w/v) Casamino acids, however, formycin was produced only after the end of exponential growth. The intracellular ppGpp pool increased gradually towards the end of exponential growth and was maximal at the beginning of formycin production. After shift down from Casamino acids medium to synthetic medium, the ppGpp pool increased immediately, while the GTP pool decreased; under such conditions, the ability to produce formycin increased eightfold. Relaxed (rel) mutants, the first isolated for a Streptomyces species, were found at high incidence (10%) among spontaneous thiopeptin-resistant isolates and had severely reduced abilities to accumulate ppGpp. These rel mutants also failed to produce formycin under the usual culture conditions and exhibited numerous pleiotropic effects such as an inability to produce melanin and an extended delay of aerial mycelium formation. Thus Streptomyces sp. exhibited a typical stringent response, and the response initiated (or was needed for) the induction of secondary metabolism. The response may have also participated in the initiation of aerial mycelium formation by decreasing the intracellular GTP pool.
链霉菌属MA406 - A - 1在合成培养基中与细胞生长同时产生甲酰肌苷（一种核苷抗生素）。然而，当合成培养基中添加1%（w/v）的酪蛋白氨基酸时，甲酰肌苷仅在指数生长结束后产生。细胞内的ppGpp库在指数生长接近结束时逐渐增加，并在甲酰肌苷产生开始时达到最大值。从酪蛋白氨基酸培养基转移到合成培养基后，ppGpp库立即增加，而GTP库减少；在这种条件下，产生甲酰肌苷的能力增加了八倍。松弛型（rel）突变体是首次从链霉菌属物种中分离得到的，在自发硫肽素抗性分离株中发生率很高（10%），并且积累ppGpp的能力严重降低。这些rel突变体在通常的培养条件下也不能产生甲酰肌苷，并且表现出许多多效性效应，如不能产生黑色素和延长气生菌丝体形成的延迟。因此，链霉菌属表现出典型的严谨反应，并且该反应启动（或为）次级代谢的诱导所必需。该反应可能还通过降低细胞内GTP库参与了气生菌丝体形成的启动。
