O-heterocyclic derivatives with antibacterial properties from marine bacterium Bacillus subtilis associated with seaweed, Sargassum myriocystum.
The brown seaweed, Sargassum myriocystum associated with heterotrophic bacterium, Bacillus subtilis MTCC 10407 (JF834075) exhibited broad-spectra of potent antibacterial activities against pathogenic bacteria Aeromonas hydrophila, Vibrio vulnificus, and Vibrio parahaemolyticus. B. subtilis MTCC 10407 was found to be positive for polyketide synthetase (pks) gene, and therefore, was considered to characterize secondary metabolites bearing polyketide backbone. Using bioassay-guided fractionation, two new antibacterial O-heterocyclic compounds belonging to pyranyl benzoate analogs of polyketide origin, with activity against pathogenic bacteria, have been isolated from the ethyl acetate extract of B. subtilis MTCC 10407. In the present study, the secondary metabolites of B. subtilis MTCC 10407 with potent antibacterial action against bacterial pathogens was recognized to represent the platform of pks-1 gene-encoded products. Two homologous compounds 3 (3-(methoxycarbonyl)-4-(5-(2-ethylbutyl)-5,6-dihydro-3-methyl-2H-pyran-2-yl)-butyl benzoate) and 4 [2-(8-butyl-3-ethyl-3,4,4a,5,6,8a-hexahydro-2H-chromen-6-yl)-ethyl benzoate] also have been isolated from the ethyl acetate extract of host seaweed S. myriocystum. The two compounds isolated from ethyl acetate extract of S. myriocystum with lesser antibacterial properties shared similar structures with the compounds purified from B. subtilis that suggested the ecological and metabolic relationship between these compounds in seaweed-bacterial relationship. Tetrahydropyran-2-one moiety of the tetrahydropyrano-[3,2b]-pyran-2(3H)-one system of 1 might be cleaved by the metabolic pool of seaweeds to afford methyl 3-(dihydro-3-methyl-2H-pyranyl)-propanoate moiety of 3, which was found to have no significant antibacterial activity. It is therefore imperative that the presence of dihydro-methyl-2H-pyran-2-yl propanoate system is essentially required to impart the greater activity. The direct involvement of polarisability (Pl) with the target bioactivity in 2 implied that inductive (field/polar) rather than the steric effect (parachor) appears to be the key factor influencing the induction of antibacterial activity. The present work may have a footprint on the use of novel O-heterocyclic polyketide products from seaweed-associated bacterium for biotechnological, food, and pharmaceutical applications mainly as novel antimicrobial secondary metabolites.
Marine Biotechnology Division, Central Marine Fisheries Research Institute, Ernakulam North, P.B. No. 1603, Cochin, India. kajal_cmfri@yahoo.com.
Kajal
K
Chakraborty
Marine Biotechnology Division, Central Marine Fisheries Research Institute, Ernakulam North, P.B. No. 1603, Cochin, India.
Bini
B
Thilakan
Crustacean Fisheries Division, Central Marine Fisheries Research Institute, Ernakulam North, P.B. No. 1603, Cochin, India.
Rekha Devi
RD
Chakraborty
Marine Biotechnology Division, Central Marine Fisheries Research Institute, Ernakulam North, P.B. No. 1603, Cochin, India.
Vamshi Krishna
VK
Raola
Marine Biotechnology Division, Central Marine Fisheries Research Institute, Ernakulam North, P.B. No. 1603, Cochin, India.
Minju
M
Joy
D000333:Aeromonas / Q000187:drug effects; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D059001:Aquatic Organisms / Q000737:chemistry / Q000382:microbiology; D001412:Bacillus subtilis / Q000737:chemistry* / Q000302:isolation & purification*; D001688:Biological Products / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D044647:Sargassum / Q000737:chemistry* / Q000382:microbiology; D014733:Vibrio / Q000187:drug effects
D000900:Anti-Bacterial Agents; D001688:Biological Products; D006571:Heterocyclic Compounds
Antibacterial activity; O-heterocyclic pyrans; Polyketide synthase; Sargassum myriocystum; Seaweed; Seaweed-associated marine bacteria