Characterization of reutericyclin produced by Lactobacillus reuteri LTH2584

Lactobacillus reuteri LTH2584 exhibits antimicrobial activity that can be a ttributed neither to bacteriocins nor to the production of reuterin or orga nic acids. We have purified the active compound, named reutericyclin, to ho mogeneity and characterized its antimicrobial activity. Reutericyclin exhib ited a broad inhibitory spectrum including Lactobacillus spp,, Bacillus sub tilis, B. cereus, Enterococcus faecalis, Staphylococcus aureus, and Listeri a innocua, It did not affect the growth of gram-negative bacteria; however, the growth of lipopolysaccharide mutant strains of Escherichia coli was in hibited. Reutericyclin exhibited a bactericidal mode of action against Lact obacillus sanfranciscensis, Staphylococcus aureus, and B. subtilis and trig gered the lysis of cells of L, sanfranciscensis in a dose-dependent manner. Germination of spores of B. subtilis was inhibited, but the spores remaine d unaffected under conditions that do not permit germination. The fatty aci d supply of the growth media had a strong effect on reutericyclin productio n and its distribution between producer cells and the culture supernatant, Reutericyclin was purified from cell extracts and culture supernatant of L, reuteri LTH2584 cultures grown in mMRS by solvent extraction, gel filtrati on, RP-C-8 chromatography, and anion-exchange chromatography, followed by r echromatography by reversed-phase high-pressure liquid chromatography, Reut ericyclin was characterized as a negatively charged, highly hydrophobic mol ecule with a molecular mass of 349 Da, Structural characterization (A, Holt zel, M, G, Ganzle, G, J, Nicholson, W. P, Hammes, and G, Jung, Angew, Chem, Int. Ed. 39:2766-2768, 2000) revealed that reutericyclin is a novel tetram ic acid derivative. The inhibitory activity of culture supernatant of L, re uteri LTH2584 corresponded to that of purified as well as synthetic reuteri cyclin.