THE PHYSIOLOGY AND BIOSYNTHESIS OF SECONDARY METABOLITES

Recently, several excellent reviews appeared /9, 12, 15, 29/ summarizi ng new findings of the last years and describing the topic in the new interconnections. The signalling systems through which changes in envi ronmental conditions affecting the growth of microorganism are sensed, transmitted and converted into mechanisms controlling the production of antibiotic can now be investigated with the techniques of molecular genetics. Evidence has been accumulated that demonstrated the key rol es played by diffusible molecules in regulating cellular differentiati on even among prokaryotic microorganisms. This is exemplified by A-fac tor and its analogues, which act as autoregulators for morphological d ifferentiation and secondary metabolism in Streptomyces. In our articl e we have concentrated on the physiological changes, which can occur d uring the growth in natural environment or during cultivation under la boratory conditions. Recent evidence for the presence of molecular sig nalling systems in Streptomyces is reviewed, along with the inherent i mplications. The constitution of the metabolic type during the first h ours of cultivation has been previously reviewed /36/.