Cloning of Genes in Streptomycetes for Secondary Metabolism
Streptomycetes are Gram-positive bacteria with an extremely high guanine plus cystosine content (70 to 73%). Their capability to produce the great majority of secondary metabolites including most of the antibiotics makes them industrially important. A complex process of morphological differentiation displayed by Streptomyces also has biologically interesting aspects. A close relationship of secondary metabolism with cell differentiation is well recognized in streptomycetes. It seems reasonable to assume that multiple genes involved in both the complex processes are controlled by a common regulatory gene or substance.
A representative of such regulatory substances is A-factor (2-isocaρryloyl-3R-hydroxymethyl-γ-butyrolactone; Mori, 1983) which was originally found by Khokhlov et al. (1967) in the culture broth of Streptomyces griseus (Figure 1). A-factor is a self-regulatory substance or bioregulator essential for streptomycin production, streptomycin resistance, and spore formation in this organism (Khokhlov et al., 1973; Khoklov, 1980; Hara and Beppu, 1982a, 1982b). A-factor-deficient mutants of S. griseus simultaneously lose streptomycin production and resistance, and spore forming ability. In such mutants, addition of A-factor at a concentration of 10-9 M restores all the defects. These features of A-factor are similar to hormones in eukaryotes.
KeywordsSecondary Metabolism Pigment Production Streptomyces Strain Streptomyces Griseus Streptomycin Resistance
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