Adaptation of Bacillus subtilis to fatty acids

A fatty acid from the diatom Phaeodactylum tricornutum is antibacterial against diverse bacteria including multi-resistant Staphylococcus aureus (MRSA)

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.

Fatty acids and monoacylglycerols inhibit growth of Staphylococcus aureus

Staphylococcus aureus causes a variety of human infections including toxic shock syndrome, osteomyelitis, and mastitis. Mastitis is a common disease in the dairy cow, and S. aureus has been found to be a major infectious organism causing mastitis. The objectives of this research were to determine which FA and esterified forms of FA were inhibitory to growth of S. aureus bacteria. FA as well as their mono-, di-, and triacylglycerol forms were tested for their ability to inhibit a human toxic shock syndrome clinical isolate (MN8) and two S. aureus clinical bovine mastitis isolates (305 and Novel). The seven most potent inhibitors across all strains tested by minimum inhibitory concentration analysis included lauric acid, glycerol monolaurate, capric acid, myristic acid, linoleic acid, cis-9, trans-11 conjugated linoleic acid, and trans-10, cis-12 conjugated linoleic acid. Some of these lipids were chosen for 48-h growth curve analysis with a bovine mastitis S. aureus isolate (Novel) at doses of 0, 20, 50, and 100 microg/mL except myristic acid, which was tested at 0, 50, 100, and 200 microg/mL. The saturated FA (lauric, capric, myristic) and glycerol monolaurate behaved similarly and reduced overall growth. In contrast, the polyunsaturated FA (linoleic and cis-9, trans-11 conjugated linoleic acid) delayed the time to initiation of exponential growth in a dose-dependent fashion. The results suggest that lipids may be important in the control of S. aureus during an infection.