Detection and Expression of Biosynthetic Genes in Actinobacteria ...

BERVANAKIS, G.Chapter 1: INTRODUCTIONmetabolites is narrow, between 5-10 degrees (Iwai & Ōmura, 1982). In the case ofstreptomycin production by Streptomyces griseus, an increase of 1 o C at the thresholdtemperature results in an 80% reduction in antibiotic production (Dunn, 1985).Secondary metabolite producing actinobacteria are mesophilic, with growth andsecondary metabolism production being optimal at 28 o C (Iwai & Ōmura, 1982).Furthermore, thermophilic actinobacteria found in extreme environments with highertemperatures requirements at 40 o C have been shown to produce novel secondarymetabolites (James et al., 1991).Temperature dependence can be used in the regulation of expression of metabolites.Kuznetsov et al. (1984) found that subjecting the antibiotic producing S. galbus totwo different temperatures, could be used to control the type of secondary metabolitebeing produced.Saccharopolyspora erythraea(erythromycin)Streptomyces aureofaciens(chlorotetracycline)Streptomyces tenebrariusNocardia mediterranei (rifamycin)Streptomyces niveus (novobiocin)Streptomycesjamaicensis(monamycin)Streptomycesgriseus var. purpureus(viomycin)Streptomyces griseus (streptomycin)Streptomyces cinnamonensis(monensin)15 20 25 30 35 40Temperature o CFigure 16. The influence of temperatures permitting vegetative growth onsecondary metabolism. Ovals represent temperature at which maximal yield ofsecondary metabolite is obtained; arrow tips represent temperatures at which minimalyields of secondary metabolite are obtained (adapted from Weinberg, 1974)_____________________________________________________________________43