Streptomycetes are multicellular bacteria with a complex life cycle. They are best known for their great potential for the synthesis of broad-spectrum antibiotics, which include tetracyclines of significant commercial importance. For decades, Streptomyces rimosus has been used to produce oxytetracycline (OTC) whose annual consumption exceeds 108 kg. Antibiotic biosynthesis is controlled by complex signaling pathways that include protein phosphorylation. In order to elucidate the regulatory mechanisms involved in the processes responsible for bacterial growth and OTC synthesis, the (phospho)proteome of S. rimosus G7 and a high OTC producer (strain 23383) was investigated for the first time using mass spectrometry in this doctoral dissertation. The dynamics of (phospho)proteomes during the growth of these bacteria was determined and results were correlated with the processes involved in antibiotic biosynthesis and cell differentiation. In total, 4053 proteins (~ 50% of proteomes) and 433 phosphoproteins were identified, of which 203 phosphoproteins were found only in strain 23383. Functional characterization and analysis of phosphorylation dynamics of these proteins gave a completely new insight into streptomycete phosphoproteins in general. So far undescribed posttranslational modification of a number of proteins important for cell division and metabolism, as well as antibiotic synthesis and stress response, has been identified.