Various fatty acids of branched nature possess fungistatic and bacteriostatic properties. Some of these, particularly those of iso-configuration, strongly enhance the effect of conventional antimicrobial agents that act inside the cell membrane. A relation between this biological effect and the collapse properties of the corresponding monomolecular surface film on water has been observed. In this work, a series of fatty acids with a slightly smaller end group than isopropyl, the c-cyclopropane fatty acids, as well as one possessing a somewhat larger end group, the neo-branched fatty acids, have been examined. The wcyclopropane fatty acids were found to be more fungistatic than the iso-acids studied earlier. Furthermore, both cyclopropane and neo-fatty acids of short chain lengths exhibited synergistic effects in combination with tetramethylthiuramdisulfide.The antimicrobial activity of various simple lipids and a model study of their mode of action have earlier been reported (8). The strongest biological effects were observed with branched fatty acids. The swelling ofhyphae ofFusarium roseum by iso-fatty acids was intexpretated as evidence for an increase in the permeability of the plasma membranes. An expected consequence of this would be the possibility ofobtaining a synergistic effect in the presence of other antimicrobial substances which act inside the plasma membrane, and such enhancement effects were also observed. This paper concerns the antimicrobial activity of other fatty acids, selected with the guidance of our earlier results. The previous work showed that the strongest effect was obtained when the branches were located near the end of the hydrocarbon chains. It was also evident that the size of such an end group should not differ much from an iso-methyl configuration. A series of compounds with a slightly smaller end group, c-cyclopropane fatty acids, as well as one possessing a somewhat larger end group, neo-branched fatty acids, therefore was examined.MATERIALS AND METHODS Preparation of lipids. Since the fatty acids (except 9-cyclopropanenonanoic acid) have not been previously reported in the literature, their preparation is given in some detail. Detailedphysical and chemical characteristics will be published elsewhere.Neo-fatty acids. A series of fatty acids, the neoisomers of the acids with 16, 18, 20, 22, and 24 carbon atoms, has been synthesized by Sobotka (Fluka AG, Buchs, Switzerland) was alkylated by refluxing it with 42.2 g ofthe iodoester in the presence of 76 g of potassium carbonate in 100 ml of dry methyl isobutylketon for 18 h.The reaction mixture was acidified with diluted hydrochloric acid and extracted with ether. After washing, drying, and evaporation, 38 g of crude alkylated keto ester was obtained. Hydrolysis and ketonic cleavage of the alkylation product was effected by adding a solution of 35 g of potassium hydroxide in 45 ml of water and 100 ml of ethanol and refluxing the mixture overnight. The reaction mixture was acidified and extracted with ether. The residue obtain...
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.
The object of this work was to develop a method for determination of the growth of Myxocuccus virescens in liquid medium. The bacteria were grown in N III‐B medium in 100 ml Kjeldahl flasks, which were fixed on a disc forming an angle of 50 degrees with the horizontal plane. The disc was rotated two full revolutions per minute. The total nitrogen content of the washed swarms, developing on the glass walls of the flasks, was used as an expression for the myxobacterial growth. After a lag the bacteria grown in total darkness had a growth phase, approximately exponential, of about 270 hours, which was followed by a steep phase of decline. When the bacteria were illuminated daily for a short period, a lag of 50–200 hours appeared in the middle of the exponential growth phase, after which a new exponential growth phase began. This second growth seemed to depend on variants insensitive to light induced lysis. The increase of enzymes, active on casein and autoclaved aerobacter cells, closely followed the first part of the growth curve. However both activities began to decrease before the growth maximum. No sign of proteolytic activity or lytic activity on autoclaved aerobacter cells could be detected after about 700 hours' incubation. In illuminated flasks it is shown that the production of yellow pigments in culture solution is sharply increased at the end of the exponential growth phase. The lytic enzymes of M. virescens seem to be extracellular, secreted during the exponential phase of growth. No activity was exhibited by washed cell swarms, even if they were sonically disintegrated.
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