A Fatty Acid from the Diatom Phaeodactylum tricornutum is Antibacterial Against Diverse Bacteria Including Multi-resistant Staphylococcus aureus (MRSA)

Abstract

Pathogenic bacteria, such as multidrug-resistant Staphylococcus aureus (MRSA), which are not susceptible to most conventional antibiotics, are causing increased concern in healthcare institutions worldwide. The discovery of novel antibacterial compounds for biomedical exploitation is one avenue that is being pursued to combat these problematic bacteria. Marine eukaryotic microalgae are known to produce numerous useful products but have attracted little attention in the search for novel antibiotic compounds. Cell lysates of the marine diatom, Phaeodactylum tricornutum Bohlin, have been reported to display antibacterial activity in vitro, but the compounds responsible have not been fully identified. In this paper, using column chromatography and reversed-phase high-performance liquid chromatography, we report the isolation of an antibacterial fatty acid. Mass spectrometry and (1)H-nuclear magnetic resonance spectroscopy revealed it to be the polyunsaturated fatty acid, eicosapentaenoic acid (EPA). We show that EPA is active against a range of both Gram-positive and Gram-negative bacteria, including MRSA, at micromolar concentrations. These data indicate that it could find application in the topical and systemic treatment of drug-resistant bacterial infections.

Differential antibacterial activities of fusiform and oval morphotypes of Phaeodactylum tricornutum (Bacillariophyceae)

“…:2 n-4, C16:3 n-4 and C16:4 n-1 (P , 0.05; Bonferroni correction) but significantly lower proportions of C16:0, C20:4 n-6 and C20:6 n-3 (P , 0.05; Bonferroni correction). Extracts from enriched cultures did not differ significantly in the sum proportion of the three antibacterial fatty acids (EPA, HTA and PA) isolated from similar extracts in previous studies (Desbois et al, 2008(Desbois et al, , 2009 N ¼ 10; data given as mean +1 SD to two decimal places. Table 2.…”

“…Mass of fatty acids attributable to each cell in methanol cell extracts from cultures enriched to contain either .71% fusiform cells or 100% oval cells showing that cells in the fusiform-enriched cultures contained significantly greater masses of C14:0, C16:2 n-4 and C16:3 n-4 (P , 0.05; Bonferroni correction). Moreover, extracts from fusiform-enriched cultures contained a significantly greater mass of fatty acids in total (P , 0.05), as well as a significantly greater total mass of three antibacterial fatty acids (EPA, HTA and PA) isolated from similar extracts previously (P , 0.05; Desbois et al, 2008Desbois et al, , 2009 …”

“…The present study now shows that extracts from fusiform cells contain a greater quantity than the ovals of the fatty acids, EPA, HTA and PA, (42.7 and 36.6 Â 10 213 g, respectively). These are known to have strong antibacterial activity against our test bacterium, Staphylococcus aureus, as well as various marine bacteria (Desbois et al, 2008(Desbois et al, , 2009. Greater quantities of antibacterial free fatty acids in the extracts from fusiform cells may be due to fusiform cells containing more lipid as a proportion of cell composition than the oval cells or alternatively, the fusiform cells may be more fragile due to their shape and cell wall structure compared with the oval cell, which is more siliceous and rigid (Lewin et al, 1958;Borowitzka & Volcani, 1978;Francius et al, 2008).…”

“…Methanol extracts of laboratory grown cultures of P. tricornutum are known to have growth inhibitory effects in vitro against Gram-positive and Gram-negative bacteria of marine or non-marine origin (Duff et al, 1966;Kellam & Walker, 1989;Desbois et al, 2008Desbois et al, , 2009. We have shown that certain unsaturated free fatty acids are responsible for the bactericidal properties of P. tricornutum methanol extracts, namely eicosapentaenoic acid (C20:5 n-3; EPA) (Desbois et al, 2009), (6Z, 9Z, 12Z )-hexadecatrienoic acid (C16:3 n-4; HTA) and palmitoleic acid (C16:1 n-7; PA) (Desbois et al, 2008). In this paper, therefore, we compare the antibacterial activities and fatty acid compositions of cell extracts derived from cultures highly enriched with either oval or fusiform cells.…”

The inhibitory effect of a non-yessotoxin-producing dinoflagellate, Lingulodinium polyedrum (Stein) Dodge, towards Vibrio vulnificus and Staphylococcus aureus

“…Their ability to withstand environmental stress and outcompete other marine organisms is related to their capacity to produce a vast array of secondary metabolites, which have considerable value in the biotechnology, aquaculture, health and food industries (Anderson, 1996). Likewise, several studies have reported antibacterial activity in the cell lysates or extracts of various microalgal species (Desbois et al, 2009;Blunt et al, 2011;de Jesus Raposo et al, 2013).…”