AUTHOR=Alharbi Nada K. , Azeez Zahraa Falah , Alhussain Haitham Mohammed , Shahlol Aisha M. A. , Albureikan Mona Othman I. , Elsehrawy Mohamed Gamal , Aloraini Ghfren S. , El-Nablaway Mohammad , Khatrawi Elham Mohammed , Ghareeb Ahmed 

TITLE=Tapping the biosynthetic potential of marine Bacillus licheniformis LHG166, a prolific sulphated exopolysaccharide producer: structural insights, bio-prospecting its antioxidant, antifungal, antibacterial and anti-biofilm potency as a novel anti-infective lead

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1385493

DOI=10.3389/fmicb.2024.1385493

ISSN=1664-302X

ABSTRACT=<p>The escalating global threat of antimicrobial resistance necessitates prospecting uncharted microbial biodiversity for novel therapeutic leads. This study mines the promising chemical richness of <italic>Bacillus licheniformis</italic> LHG166, a prolific exopolysaccharide (EPSR2-7.22 g/L). It comprised 5 different monosaccharides with 48.11% uronic acid, 17.40% sulfate groups, and 6.09% N-acetyl glucosamine residues. EPSR2 displayed potent antioxidant activity in DPPH and ABTS<sup>+</sup>, TAC and FRAP assays. Of all the fungi tested, the yeast <italic>Candida albicans</italic> displayed the highest susceptibility and antibiofilm inhibition. The fungi <italic>Aspergillus niger</italic> and <italic>Penicillium glabrum</italic> showed moderate EPSR2 susceptibility. In contrast, the fungi <italic>Mucor circinelloides</italic> and <italic>Trichoderma harzianum</italic> were resistant. Among G+ve tested bacteria, <italic>Enterococcus faecalis</italic> was the most susceptible, while <italic>Salmonella typhi</italic> was the most sensitive to G−ve pathogens. Encouragingly, EPSR2 predominantly demonstrated bactericidal effects against both bacterial classes based on MBC/MIC of either 1 or 2 superior Gentamicin. At 75% of MBC, EPSR2 displayed the highest anti-biofilm activity of 88.30% against <italic>B. subtilis</italic>, while for G−ve antibiofilm inhibition, At 75% of MBC, EPSR2 displayed the highest anti-biofilm activity of 96.63% against <italic>Escherichia coli</italic>, Even at the lowest dose of 25% MBC, EPSR2 reduced biofilm formation by 84.13% in <italic>E. coli</italic>, 61.46% in <italic>B. subtilis</italic>. The microbial metabolite EPSR2 from <italic>Bacillus licheniformis</italic> LHG166 shows promise as an eco-friendly natural antibiotic alternative for treating infections and oxidative stress.</p>