Participation of (p)ppGpp molecules in the formation of “stringent response” in bacteria, as well as in the biosynthesis of antibiotics and morphological differentiation in actinomycetes

Abstract

Stringent response is a pleiotropic physiological response of cells caused by deficiency of aminoacetylated tRNAs and, correspondingly, by the arrest of protein synthesis. This response can experimentally be induced by amino acid deficiency in a culture medium and limitation of the aminoacylation capacity of tRNA molecules even in the presence of the respective amino acids in the cell. Many traits of this response indicate its dependence on the accumulation of ppGpp molecules. There are links between the growth rate of actinomycetes and the biosynthesis of secondary metabolites by the bacteria. In particular, it has been established that the introduction of additional relA gene copies of the ppGpp synthetase can affect the production of antibiotics in streptomycetes. The survey presents the authors’ own experimental data obtained in the studies on the effect of heterologous relA gene expression in Streptomyces nogalater, the nogalamycin producer.