Antibacterial and antilarval compounds from marine gorgonian-associated bacterium Bacillus amyloliquefaciens SCSIO 00856

Abstract

It is well understood that corals harbor diverse microbial communities. Recently, many coral-associated bacteria have been characterized as sources of marine natural products, especially as the coral surface is more nutrient rich than seawater or even sediments. 1,2 Colonization of coral surfaces by bacteria and other microorganisms is mostly nondestructive to corals. Owing to the close spatial vicinity of these biofilm-forming bacteria, it can be expected that the indigenous microbial population is adapted to competitive conditions. 3 The production of secondary metabolites is a common adaptation of these bacteria to compete in such microenvironments. There have been few reports documented on exploration of coralassociated bacteria in the South China Sea as a source of secondary metabolites.In order to obtain biologically active natural products from coral-associated bacteria, we studied the marine bacterium Bacillus amyloliquefaciens SCSIO 00856 isolated from the South China Sea gorgonian Junceella juncea. In the preliminary experiments, we found that the culture broth of the strain had strong antibacterial activity towards three bacteria (Escherichia coli, Bacillus subtilis, and Staphyloccocus aureus) and antilarval activity towards laboratory-reared bryozoan Bugula neritina larvae. In this study, a new 24-membered ring lactone, macrolactin V (1) (Figure 1), together with four known compounds, macrolactin S (2), 4 4-butoxyphenol (3), 5 4-propoxyphenol (4), 6 and 4-ethoxyphenol (5), 6 was isolated from a culture broth of the strain. Macrolactins are polyene macrolides containing a 24-membered lactone ring. About 20 macrolactins have been chemically characterized, including macrolactins A-U, 7-O-succinyl macrolactin A, and 7-O-succinyl macrolactin F, from marine Bacillus sp. sediment isolate, and 7-O-malonyl macrolactin A from Bacillus subtilis soil isolate. 4,7-13 Some of these compounds showed strong antibacterial, anti-tumor, and antivirus activities. 4,7,[9][10][11][12][13] The antibacterial activity of 1-5 against four bacterial strains and the antilarval activity of 3-5 against larval settlement of Bugula neritina and Balanus amphitrite larvae were evaluated. This paper deals with the isolation, structural elucidation of 1 and biological activity of 1-5.The producing strain, Bacillus amyloliquefaciens SCSIO 00856, was isolated from the gorgonian coral Junceella juncea in Sanya, Hainan province, China. The strain culture (2 ml) was used to inoculate 50 ml seed medium consisting of 0.4% yeast extract, 0.4% glucose, 0.5% malt meal, and 1.8% sea salt (pH 7.3), in a 250-ml flask. A volume of 20 ml of the resulting culture was used to inoculate 400 ml of the seed medium, in a 1-l flask. The culture was incubated at 27 1C on a rotary shaker operating at 150 r.p.m. for 5 days. The resulting 400-ml culture was used to inoculate 120 l of production medium, in a 200-l fermenter, containing the following components per liter of water: yeast extract 4 g, malt meal 5 g, glucose 4 g, and sea salt 18 g. The production fe...

Diversity of Secondary Metabolites from Marine Bacillus Species: Chemistry and Biological Activity

“…Macrolactins V ( 86 ) and S ( 69 ) (Figure 17 and Figure 21) were isolated from the culture broth of a marine bacterium, B. amyloliquefaciens SCSIO 00856, which was isolated from a South China Sea gorgonian, Junceella juncea [48]. Macrolactin V ( 86 ) exhibited potent antibacterial activity against E. coli , B. subtilis and S. aureus with an MIC value of 0.1 µg/mL, and no activity against B. thuringiensis .…”

“…Macrolactin V ( 86 ) exhibited potent antibacterial activity against E. coli , B. subtilis and S. aureus with an MIC value of 0.1 µg/mL, and no activity against B. thuringiensis . Macrolactin S ( 69 ) showed strong antibacterial activity against both E. coli and S. aureus with MIC values of 0.3 and 0.1 µg/mL, respectively, but weak activity against B. subtilis (MIC 100 µg/mL), which indicated that the configuration of 7-OH may affect the antibacterial activity of the epimers 86 and 69 [48]. …”

Diversity and antimicrobial potential in sea anemone and holothurian microbiomes

“…Therefore, they are excellent candidates for the search of symbiotic bacteria with antimicrobial potential. Cnidarians, as soft corals, gorgonians and sea anemones, have a high diversity of symbiotic bacteria [ 27 , 28 ], especially as the coral surface is more nutrient-rich than seawater or sediments [ 29 , 30 ]. Indeed, some authors have detected coral-associated bacteria as sources of antimicrobial products [ 27 , 31 – 33 ].…”

Natural product diversity of actinobacteria in the Atacama Desert

“…The structures most closely related to atacamycins and chaxalactins are the 24-membered polyketides of the macrolactin family. To date, macrolactins A-V have been isolated from marine and soil bacterial isolates and have been shown to possess antibacterial, antilarval, antiviral, and antitumor activities (Gao et al 2010). …”