Antimicrobial Potential of Bacillus kochii Strain Isolated from Marigold

Endophytic bacteria are an untapped source of bioactive compounds with potential antimicrobial applications. This study focused on isolating and evaluating endophytic bacterial strains from marigold (Tagetes spp.) for their antimicrobial activity and optimizing the production of bioactive compounds under various conditions. Twenty bacterial isolates were obtained from roots, stems, leaves, and flowers of marigold, with isolate F2 exhibiting the highest antimicrobial activity. Screening against E. coli, S. aureus, P. aeruginosa, and C. albicans revealed significant zones of inhibition, particularly for F2 (25 mm against E. coli and 23 mm against C. albicans), demonstrating its potential as a promising antimicrobial producer. The effects of temperature, carbon, and nitrogen sources, pH, and incubation time on antimicrobial production were investigated. Optimal production was observed at 35°C, pH 7.0, and 72 hours of incubation, with lactose and yeast extract identified as the most effective carbon and nitrogen sources, respectively. Purification through column chromatography and HPLC identified a bioactive compound at 12.254 minutes retention time, with mass spectrometry confirming a molecular weight of ~575 Da. Comparative analysis revealed the novelty and enhanced efficacy of this compound, highlighting its potential as a lead molecule for novel antibiotic development. This study uniquely explores endophytic bacteria from marigold as a source of bioactive compounds and identifies F2 as Bacillus kochii with potent antimicrobial activity. The structural analysis of a novel compound further underscores its pharmaceutical significance, contributing to the search for new antibiotics to combat antimicrobial resistance.