ANTIBIOTIC EFFECT OF LINOLENIC ACID FROM CHLOROCOCCUM STRAIN HS-101 AND DUNALIELLA-PRIMOLECTA ON METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

Methanol extracts from Chlouocpccum strain HS-101 and Dunaliella primo lecta strongly inhibited the growth of a strain of methicillin-resista nt Staphylococcus aureus (MRSA), which is causing serious problems in Japanese hospitals. So that the anti-MRSA substance(s) could be purifi ed and identified, the growth medium was improved for antibiotic produ ction. When the two strains were cultured in their improved media, ant ibiotic production by Chlorococcum strain HS-101 was 1.8-fold that in the standard BG-11 medium, and production by D. primolecta was 2.3-fol d. The activity pattern of fractions eluted by silica-gel or gel-perme ation chromatography suggested that both strains produced two antibiot ic substances. Identification of the purified substances by NMR and GC -MS showed that one of the active substances in both strains was cr-li nolenic acid. Ten fatty acids from other sources were tested, and it w as found that unsaturated fatty acids had antibiotic activity against MRSA, with the highest activity that of gamma-linolenic acid.