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Previously Undescribed Antibacterial Polyketides from Heterotrophic Bacillus amyloliquefaciens Associated with Seaweed Padina gymnospora


A heterotrophic marine bacterium Bacillus amyloliquefaciens isolated from seaweed Padina gymnospora exhibited broad spectra of antibacterial activities against pathogenic bacteria Aeromonas hydrophila, Vibrio harveyi, Vibrio vulnificus, and Vibrio parahaemolyticus. The seaweed-associated B. amyloliquefaciens was recognized to possess functional type I polyketide synthase-1 (pks-1) gene, and was used to isolate four homologous compounds with polyketide frameworks. The compounds were characterized as 11-(15-butyl-13-ethyl-tetrahydro-12-oxo-2H-pyran-13-yl) propyl-2-methylbenzoate (1), 9-(tetrahydro-12-isopropyl-11-oxofuran-10-yl)-ethyl-4-ethoxy-2-hydroxybenzoate (2), 12-(aminomethyl)-11-hydroxyhexanyl-10-phenylpropanoate (3), and 7-(14-hydroxypropan-13-yl)-8-isobutyl-7,8-dihydrobenzo[c]oxepin-1(3H)-one (4) by comprehensive nuclear magnetic resonance and mass spectroscopic experiments. The compounds 14 displayed significant antibacterial activities against clinically important pathogens V. parahaemolyticus and V. vulnificus (inhibitory zone diameter of ≥15 mm, 100 mcg on disk). The electronic and hydrophobic parameters appeared to hold a conspicuous part in directing the antibacterial properties of the compounds. This study revealed seaweed-associated B. amyloliquefaciens as potential source of antimicrobial polyketides for pharmaceutical applications.

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The work is funded by the Indian Council of Agricultural Research (ICAR) Network Project High Value Compounds (grant no. HVC/ICAR 2012–2017). The authors thank the Director, Central Marine Fisheries Research Institute, for his valuable guidance and support. Thanks are due to the Head, Marine Biotechnology Division of Central Marine Fisheries Research Institute, for facilitating the research activities. B.T. and V.R. acknowledge ICAR for fellowships.

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Correspondence to Kajal Chakraborty.

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Chakraborty, K., Thilakan, B. & Raola, V.K. Previously Undescribed Antibacterial Polyketides from Heterotrophic Bacillus amyloliquefaciens Associated with Seaweed Padina gymnospora . Appl Biochem Biotechnol 184, 716–732 (2018).

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  • Seaweed associated bacterium
  • Bacillus amyloliquefaciens
  • Padina gymnospora
  • Antibacterial metabolites
  • Polyketides
  • Polyketide synthase-1