No abstract

The activity of a number of unsaturated fatty acids in inhibiting the growth of the green algaChlorella pyrenoidosa has been studied using the paper disk‐agar plate method. Acrylic and undecylenic acids were highly active, but other θ‐unsaturated fatty acids tested were only weakly active. Oleic and elaidic acids were inactive at 0.2 M, but other C18‐C22 acids with 2 to 6 double bonds were generally active down to a concentration of 0.01–0.005 M. Activity with chaulmoogric acid was noted down at 0.002–0.001 M. Diffusion rates of the acids through the agar seem to affect the size of the inhibition zones. The implications that polyunsaturated fatty acids may play a role in algal ecology are discussed.

Fatty acids cause a decrease in the absorption spectra of the antifungal polyene macrolide antibiotics nystatin, filipin, candicidin, and amphotericin B. For nystatin, fi6pin, and candicidin, this decrease in absorption could be correlated with the activity of the fatty acids in protecting the yeast Saccharomyces cerevisiae against the action of these antibiotics. With amphotericin B a correlation was observed between the decrease in absorption caused by certain derivatives of fatty acids and the protective action of these derivatives against the activity of amphotericin B on yeast. It is concluded that, like the sterols, fatty acids also interact with the polyene antibiotics and thereby reduce their effective concentrations.The polyene macrolide antibiotics are effective antifungal agents and, as a rule, are inactive against bacteria. The polyenes interact with sterols of the cell membrane to alter its structure and cause the leakage of essential metabolites (see reference 3). Lampen et al. (6) showed that when ergosterol or cholesterol was incorporated into the culture medium, yeasts were protected from the action of polyenes such as filipin, nystatin, and antimycoin.Hickey (5) has shown that the action of the polyene ascosin on the yeast Saccharomyces cerevisiae was antagonized by fatty acids, the longer-chain-length acids and the more unsaturated acids being the most effective. Ghosh and Ghosh (2), investigating the effect of various lipids on the uptake of nystatin by Candida albicans, found that the uptake was antagonized more effectively by linoleic acid than by ergosterol, cholesterol, vitamin A, or oleic acid. Sarachek and Higgins (8) showed that fatty acids could protect nonirradiated cells from damage by amphotericin B and also significantly enhance the recovery of ultraviolet light-damaged cells. The protective action increased with chain length, but the unsaturated C18 acids, oleic, linoleic, and linolenic, were less effective than saturated C18 stearic acid. Recently, Hammond and Kliger (4) showed that resistance to membrane damage of C. albicans by candicidin increased with the age of the culture. This effect was correlated with an increase in cell wall triglycerides with age. Lampen et al. (6) studied the binding of the polyene antibiotics filipin, nystatin, and antimycoin to sterols by spectrophotometric means. They found that sterols significantly reduced the absorbance of the polyenes at their absorption maxima. This was interpreted to mean that the sterols decreased the effective concentration of the polyenes in the mixture. This was borne out by the fact that the addition of isopropyl alcohol restored the absorbance because of the resolubilization of the polyenes. Bittman and Fischkoff (1), by fluorescence studies, concluded that polyene-cholesterol binding did take place in an aqueous buffer and that the binding was accomplished by hydrophobic interactions.A study was made to determine whether changes in the absorbance of polyene antibiotics could be produced by fatty acids and whether t...

Since antimicrobiol activity and toxicity to higher plants and animals often overlap, it was of interest to test mycotoxins and other fungal products on several microorganisms in order to determine whether antimicrobial activity could be used as a bioassay procedure to detect certain tvnes of mycotoxins. Materials-The diacetoxyscirpenol, T-2 toxin, roridin A and verrucarin A were purchased from Makor Chemicals, Jerusalem; the patulin and penicillic acid from Aldrich Chemical Co., Milwaukee, Wisconsin; the rubratoxin B and aflatoxins from Calbiochem, La Jolla, California. We wish to thank M. C. Bachman, IMC Chemical Group, Terre Haute, Indiana, for the zearalenone; U. L. Diener, Auburn University, Auburn, Alabama, for the citrinin; T. C. Halsall, University of Oxford, Oxford, England, for the polyporenic acid A; J. M. McGuire, Eli Lilly and Co., Indianapolis, Indiana, for the monensin; and G. B. Whitfield, Upjohn Co., Kalamazoo,Michigan, for the filipin. Assay procedure-Solutions were prepared at a concentration of 1 mg/ml and diluted 10-fold so long as activity was apparent. Paper disks (1/4 inch, Difco Laboratories, Detroit, Michigan) held by tweezers were dipped into the solutions and excess solution removed by touching the disks to the sides of the container. Approximately 20 pJ of solution are retained by the disk'). Disks were placed in triplicate or quadruplicate over the organism-seeded agar surface. Solvent controls were always run.