Abstract. Growth conditions are described for streptomycin production by Streptomyces griseus using chemically defined minimal medium and complex medium. It was found using batch cultures that early synthesis of the antibiotic occurred during growth in minimal medium but was delayed until growth began. On the other hand, certain isolates express their antimicrobial effect on all three media at the same time. Additionally, some actinomycete isolates inhibit the growth of several microorganisms simultaneously. While others inhibit the growth of a single microorganism tested, which reflects a possible specificity of the antimicrobial substances. The Streptomyces annotation server. the four hydrolases rpfA, swlB and swlC being maximal h, we reasoned that the absence of these gene products could affect vegetative growth. By examining the vegetative. The rpf gene of Micrococcus luteus encodes an essential secreted growth factor. Mol. Microbiol. 46:611-621. Google. The genus Streptomyces represents Gram-positive, filamentous bacteria living in soil. Members belonging to Streptomyces are one of the largest sources of secondary metabolites such as antibiotics, herbicides, parasiticides, immunosuppressive agents, antitumor compounds, and several other pharmaceutical compounds. An example of biological growth is a plant seed developing into a fully mature tree. At the cellular level, cell growth means an increase in size or an increase in number. In medical science, growth can be associated with pathology. For example, pathological growth may indicate a tumor, which is an abnormal mass of cells, temperature. In general, the higher the temperature, the more easily microorganisms can grow to a certain extent. Both very high and very low temperatures hinder the enzymatic processes that microorganisms depend on to survive, but individual species of microorganisms have evolved to prefer different temperature levels.