A relaxed (rel) mutant of Streptomyces coelicolor A3(2) with a missing ribosomal protein lacks the ability to accumulate ppGpp, A-factor and prodigiosin

Abstract

A relaxed (ref) mutant was found among 70 thiopeptin-resistant isolates of Streptomyces coeficofor A3(2) which arose spontaneously. The ability of the ref mutant to accumulate ppGpp during Casamino acid deprivation was reduced 10-fold compared to the wild-type. Analysis of the ribosomal proteins by two-dimensional PAGE revealed that the mutant lacked a ribosomal protein, tentatively designated ST-L11. It was therefore classified as a vefC mutant. The mutant was defective in producing A-factor and the pigmented antibiotic prodigiosin, in both liquid and agar cultures, but produced agarase normally. Production of actinorhodin, another pigmented antibiotic, was also abnormal; it appeared suddenly in agar cultures after 10 d incubation. Although aerial mycelium still formed, its appearance was markedly delayed. Whereas liquid cultures of the parent strain accumulated ppGpp, agar cultures accumulated only trace amounts. Instead, a substance characterized only as an unidentified HPLC peak accumulated intracellularly in the late growth phase, just before aerial mycelium formation and antibiotic production. This substance did not accumulate in mutant cells. It was found in S. fividans 66 and S.parvufus, but not in seven other Streptomyces species tested. The significance of these observations, and the relationship of the mutant to earlier ref isolates of Streptomyces is discussed.

Guanine Nucleotides Guanosine 5′-Diphosphate 3′-Diphosphate and GTP Co-operatively Regulate the Production of an Antibiotic Bacilysin in Bacillus subtilis

“…In many cases, these mutations are found in the relA gene, which encodes the ppGpp synthetase, or the relC (ϭ rplK) gene, which codes for the ribosomal protein L11. These relaxed (rel) mutants are unable to initiate ribosome-mediated synthesis of ppGpp (2)(3)(4)(5). Therefore, the RelA and L11 proteins are thought to be essential mediators, which signal cessation to the transcriptional machinery.…”

A relA/spoT Homologous Gene from Streptomyces coelicolor A3(2) Controls Antibiotic Biosynthetic Genes

“…There are several reports that (p)ppGpp formation takes place during stringent response in several Streptomyces species (37-41, 96 -99). A relaxed (presumptively relC) mutant in S. coelicolor has been isolated (37) in which the onset of aerial mycelium formation was delayed and the production of actinorhodine and undecylprodigiosin was abnormal. The 18J strain reported here was shown to grow slower than the wild type and to have a reduced formation of spores (in agreement with the observations of Ochi (37)), but only actinorhodine was severally affected in our mutant.…”

“…Defective ribosomal (p)ppGpp synthesis was observed in relC mutants, which have an altered L11 protein in the 50 S ribosomal unit, the same subunit implicated in the binding of the RelA protein (35,36). A putative relC mutant of S. coelicolor has been isolated (37). The strain is deficient in the production of actinorhodine and undecylprodigiosin as well as in its ability to form aerial mycelium.…”

The regulation of antibiotic production in Streptomyces coelicolor A3(2)

“…The ability to clone streptomycete genes, and to examine their expression in vivo, revealed some of the basic features of gene expression in these organisms. It soon became apparent that streptomycetes possess a high degree of promoter sequence heterogeneity (Bibb e t al., 1985a;Janssen e t al., 1989;Janssen & Bibb, 1988, 1990Strohl, 1992). Some of this variability reflects the occurrence of multiple 0 factors, which confer on RNA polymerase core enzyme the ability to recognize different subsets of promoter sequences (Westpheling etal., 1985;Buttner etal., 1988).…”

“…Many streptomycete genes were found to be transcribed from more than one promoter (Bibb etal., 1985b;Buttner e t al., 1987;Janssen & Bibb, 1988, 1990Janssen e t al., 1989;Strohl, 1992), sometimes by more than one form of RNA polymerase holoenzyme (Buttner e t al., 1988 ;Westpheling & Brawner, 1989). Although the significance of this for the regulation of gene expression is not known, it may reflect changes in the availability of 0 factors and other regulatory proteins during development.…”