Switch-On Time for Act Gene Expression and Switch-Off Time of the 16S rRNA Gene for Optimization Production of Actinorhodin Antibiotic by Streptomyces coelicolor strain ATCC 10147

The aim of the study was to determine the switch-on time for Act gene expression and switch-off time of the 16S rRNA gene for optimization production of the actinorhodin antibiotic by Streptomyces coelicolor strain ATCC 10147. The full sequence of 1804 bp of the 16SrRNA gene of the S. coelicolor strain ATCC 10147 was determined, and its phylogenetic tree is given with 99.9% homology to the closest sister strains, S. coelicolor strains M1154 and A3(2). The expression switch-on time of the Act gene was determined to be after 34 h of growth, whereas the switch-off time of 16S rRNA was determined to be at 120 h of growth by the addition of chloramphenicol, which blocks the RNA enzyme peptidyl transferase center, which is located at the lower tips (acceptor ends) of the A- and P-site tRNAs, where it binds to the residues A2451 and A2452 in the 23S rRNA (component of 50S) and prevents the attachment of aminoacyl transferase to the ribosomal subunit, which inhibits peptide bond formation. The optimum growth conditions for actinorhodin production were determined in liquid growth as nutrient broth as a C-source (1% starch), N-source (K₂NO₃), P-source (K₂PO₄), Fe-source (FeCl₃-EDTA), shaking speed (200 rpm), pH 7.0, 28？C, and aerobic conditions. The extracellular and intracellular actinorhodin reached 165 mg^？1 and 88 mg^？1, respectively. The optimum growth of the strain on solid media was on nutrient agar plus 1% starch. For production of the antibiotic droplets on the colony’s surface, the strain was cultured on potato dextrose agar (PDA) for 5 days before several droplets (3 - 5) appeared on the top of each colony. The actinorhodin activity was tested against the international MRSA control strain Staphylococcus aureus ATCC 25923 and the local MR Bacillus cereus strain. The inhibition zones were 21 mm and 24 mm for the MRSA control strain Staphylococcus aureus ATCC 25923 and the local MR Bacillus cereus strain, respectively. The MIC of the actinorhodin antibiotic was 2.0 ug/ml and 4.0 ug/ml for the MRSA control strain Staphylococcus aureus ATCC 25923 and the local MR Bacillus cereus strain. The results are novel on the ON/OFF switching of interplay regulation of gene expression for optimization of actinorhodin antibiotic production by S. coelicolor strain ATCC 10147. The results also provide evidence of optimization of actinorhodin antibiotic production using