Bohne L, Winkler U
Arch Microbiol. 1979 May;121(2):181-6. doi: 10.1007/BF00689984.
Serratia marcescens SM-6 when starved for a required amino acid stops synthesizing protein and RNA and accumulates two nucleotides which co-chromatograph with ppGpp and pppGpp. These features are characteristic of bacterial strains with stringent RNA control (rel+). Two independent mutants were isolated which resemble relaxed (relA) mutants of Escherichia coli; they continue to synthesize RNA and accumulate neither ppGpp nor pppGpp when deprived of the required amino acid. The extracellular enzyme activities (nuclease, protease, lipase) of the relaxed mutants are about the same as those of the parental stringent strain when studied under standard growth conditions. Exoenzyme-deficient (nuc;prt) and exoenzyme-hyperproducing (nucsu) mutants were isolated from both stringent and relaxed strains of S. marcencens SM-6 and no change of the cellular ability to form ppGpp and pppGpp could be observed. From these results it appears that the formation of exoenzymes of S. marcescens SM-6 is independent of stringent/relaxed RNA control.
粘质沙雷氏菌SM-6在缺乏必需氨基酸时会停止合成蛋白质和RNA，并积累两种与ppGpp和pppGpp共色谱的核苷酸。这些特征是具有严格RNA控制（rel+）的细菌菌株所特有的。分离出了两个独立的突变体，它们类似于大肠杆菌的松弛（relA）突变体；当缺乏必需氨基酸时，它们继续合成RNA，既不积累ppGpp也不积累pppGpp。在标准生长条件下研究时，松弛突变体的细胞外酶活性（核酸酶、蛋白酶、脂肪酶）与亲本严格菌株的酶活性大致相同。从粘质沙雷氏菌SM-6的严格菌株和松弛菌株中都分离出了胞外酶缺陷（nuc;prt）和胞外酶高产（nucsu）突变体，未观察到细胞形成ppGpp和pppGpp的能力发生变化。从这些结果看来，粘质沙雷氏菌SM-6胞外酶的形成与严格/松弛RNA控制无关。
