Antagonistic effects ofMyxococcus xanthus on fungi: II. Isolation and characterization of inhibitory lipid factors

The chemical composition of the lipophilic excretion ofMyxococcus xanthus inhibitory to the germination of fungal spores and growth has been investigated. The inhibitory effect was attributed to a mixture of fungistatically acting fatty acids and a component of antibiotic character. The fatty acid mixture has been fully characterized and found to constitute a mixture of saturated (68%) and unsaturated (32%) structures in the C13–C17 range. The major part is methylbranched of theiso‐type, with 13‐methyltetradecanoic acid being the main component (33% of the total). The fungistatic activity of the fatty acid mixture on spore germination is attributed to the structures withiso‐configuration. The presence of unsaturation is of minor importance. Observed morphological changes of the spores and hyphae in the presence ofiso‐fatty acids suggest that they act on the plasma membrane.