Assessment of antimicrobial activity and GC-MS using culture filtrate of local marine <i>Bacillus</i> strains

Abstract

Secondary metabolites produced by <i>Bacillus</i> species from marine sources encompass a variety of compounds such as lipopeptides, isocoumarins, polyketides, macrolactones, polypeptides and fatty acids. These bioactive substances exhibit various biological activities, including antibiotic, antifungal, antiviral, and antitumor properties. This study aimed to isolate and identify a particular species of <i>Bacillus</i> from marine water and organisms that can produce bioactive secondary metabolites. Among the 73 <i>Bacillus</i> isolates collected, only 5 exhibited antagonistic activity against various viral and bacterial pathogens. The active isolates were subjected to 16S rRNA sequencing to determine their taxonomical affiliation. Among them, <i>Bacillus tequilensis</i> CCASU-2024-66 strain no. 42, with the accession number ON 054302 in GenBank, exhibited the highest inhibitory potential. It displayed an inhibition zone of 21 mm against <i>Bacillus cereus</i> while showing a minimum zone of inhibition of 9 mm against <i>Escherichia coli</i> and gave different inhibition against pathogenic fungi, the highest inhibition zone 15 mm against <i>Candida albicans</i> but the lowest inhibition zone 10 mm was against <i>Botrytis cinerea</i>, <i>Fusarium oxysporum.</i> Furthermore, it demonstrated the highest percentage of virucidal effect against the Newcastle virus and influenza virus, with rates of 98.6% and 98.1%, respectively. Furthermore, GC-MS analysis was employed to examine the bioactive substance components, specifically focusing on volatile and polysaccharide compounds. Based on these results, <i>Bacillus tequilensis</i> strain 42 may have the potential to be employed as an antiviral agent in poultry cultures to combat Newcastle and influenza, two extremely destructive viruses, thus reducing economic losses in the poultry production sector. Bacteria can be harnessed for the purpose of preserving food and controlling pathogenic fungi in both human and plant environments. Molecular docking for the three highly active derivatives 2,3-Butanediol, 2TMS, D-Xylopyranose, 4TMS, and Glucofuranoside, methyl 2,3,5,6-tetrakis-O-(trimethylsilyl) was carried out against the active sites of <i>Bacillus cereus</i>, <i>Listeria monocytogenes</i>, <i>Candida albicans</i>, Newcastle virus and influenza virus. The data obtained from molecular docking is highly correlated with that obtained from biology. Moreover, these highly active compounds exhibited excellent proposed ADMET profile.