The cultivation with non kind microorganisms induces the production of antibacterial secondary metabolites in microbes. In S. avermitilis such reaction could be monitored by analyzing the frequently observed guttation droplets, which might serve as reservoir for secondary metabolites in streptomycetes and fungi. Analyses showed that S. avermitilis formed guttation droplets mainly contained sucrose. S. avermitilis produced the sucrose from the nutrients of the medium. As reaction coculture with P. fluorescens the reduction of available sucrose amount was detected. This suggests that the sucrose could serve as energy storage, which is mobilized under the competitive pressure in the mixed culture. As well as non kind microorganisms have certain metal ions a stimulating effect on the secondary metabolism of streptomycetes. Therefore, the effects of cobalt ion stress Streptomyces coelicolor were characterized systematically. Relatively high concentration of cobalt ion in the medium induced the differentiation of a red and a blue colored phenotype of S. coelicolor. GC-MS analysis indicates that the two pigmented phenotypes produce a volatile profile different from the wild type. The volatile emission of S. coelicolor was characterized by the reduction of terpene release under cobalt ion stress. Specifically the red phenotype produced 2-tridecanone and undecylpyrrole, whereas the blue phenotype intensified its isozizaene emission. The formation of undecylprodigiosin as well as butylcycloheptylprodigiosin in the red colonies, and γ-actinorhodin, in the blue colonies was detected. These polyketides considerably contributed to pigmentation of the colored colonies. The gene expression of the colored phenotypes under cobalt ion stress was differentially regulated compared to the wild type. It can be concluded, that the development of an altered metabolite profile in S. coelicolor under cobalt ion stress is based on characteristic patterns in gene expression.