Background:
The bacterial genus Streptomyces comprises well-known producers of bioactive compounds, mainly antibiotics. Specifically, the strain Streptomyces sp. VITGV100 shows promise as a potent antimicrobial source. This study investigates the activation of cryptic biosynthetic genes within this strain through chemical elicitation to amplify the production of secondary metabolites.

Material and methods:
To achieve this, Streptomyces sp. VITGV100 was cultured in nutrient broth supplemented with 0.5% dimethyl sulfoxide (DMSO) to elicit metabolic changes over 7, 14, and 21 days. The resulting crude extracts were screened for antimicrobial activity against four human pathogens: Escherichia coli (Microbial Type Culture Collection and Gene Bank [MTCC] 1687), Pseudomonas aeruginosa (MTCC 3541), Bacillus subtilis (MTCC 2756), and Staphylococcus aureus (MTCC 737). Bioactive fractions were characterized by gas chromatography-mass spectrometry (GC-MS). Finally, identified compounds, namely lacthydrazide, were docked against target proteins: E. coli Z-ring-associated protein (5IMJ), P. aeruginosa OXA10 (4WZ5), S. aureus TyrRS (1JIJ), and B. subtilis DLTA (3E7X).

Results:
The 7-day crude extract exhibited the strongest antimicrobial activity, yielding a maximum inhibition zone of 31 mm against E. coli at 100 µg/ml and a minimum zone of 9 mm against B. subtilis at 25 µg/ml. GC-MS analysis revealed 45 distinct peaks in the included extracts versus 30 in controls, identifying lacthydrazide as a primary compound. Molecular docking confirmed the strong binding affinity of lacthydrazide to the target proteins, supporting its antimicrobial potential.

Conclusions:
Streptomyces sp. VITGV100, elicited with 0.5% DMSO, effectively activated cryptic genes to synthesize potent antibacterial compounds. These findings position this strain as a valuable resource for discovering novel antimicrobials.