Evaluation of commercial essential oil samples on the growth of postharvest pathogen Monilinia fructicola (G. Winter) Honey.

AIM: To assess the effect of several commercial essential oils samples Australian lemon myrtle (Backhousia citriodora), cinnamon bark (Cinnamomum zeylanicum), oregano (Origanum vulgare), thyme oil (Thymus vulgaris), clove bud (Eugenia caryophyllata), valerian (Valeriana officinalis) and Australian tea tree oil (Melaleuca alternifolia) on mycelium growth and spore germination of Monilinia fructicola. The effectiveness of lemon myrtle essential oil as a fumigant for the control of brown rot in nectarines was evaluated. METHODS AND RESULTS: Monilinia fructicola exhibited a different level of sensitivity to each tested essential oil with results suggesting that the essential oils provide excellent control of the pathogen with respect to mycelium growth and spore germination at very low concentrations, whereas for others higher concentrations are needed to reduce significant fungal growth. In vivo application of lemon myrtle essential oil effectively reduced the incidence of M. fructicola on noninoculated fruit. Fumigation of nectarines following inoculation did not reduce the incidence of brown rot in comparison with the inoculated control treatment. No evidence of phytotoxicity on the fruit was recorded. CONCLUSIONS: Lemon myrtle essential oil exhibited the strongest antifungal activity against M. fructicola, in vitro and to a lesser extent, under in vivo conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The results demonstrate that lemon myrtle essential oil, in particular, has potential as an antifungal agent to control M. fructicola.

Interaction of Vi antigen with proteins.

Whiteside, Roberta E. (Boston University School of Medicine, Boston, Mass.), and Edgar E. Baker. Interaction of Vi antigen with proteins. J. Bacteriol. 92:1597-1603. 1966.-Purified Vi antigen (Vi) mixed in equal amounts with bovine serum albumin (BSA) or human gamma globulin (HGG) at pH values above 4.7 formed a complex which was not precipitated by trichloroacetic acid or tungstic acid. At pH values below 4.7, the interaction between Vi and either BSA or HGG produced insoluble complexes except when excess Vi antigen was present. When sufficient Vi was present at the lower pH values, the soluble complex was not precipitated by trichloroacetic acid. Other acid polysaccharides tested did not form trichloroacetic acid-soluble complexes with BSA. When subjected to immunoelectrophoresis, the Vi-BSA complex migrated in agar at a rate different from that of either BSA or Vi alone. The complex reacted with both Vi and BSA antiserum. The addition of either BSA or Vi antiserum to a Vi-BSA complex resulted in dissociation of the complex and precipitation of either Vi or BSA, depending upon the antiserum used. Vi antigen mixed with purified O antigen from Salmonella typhosa formed a complex which migrated in agar at a rate different from that of either component alone when subjected to immunoelectrophoresis.

A new iron-containing superoxide dismutase from Escherichia coli.

Escherichia coli B, grown under aerobic conditions, contains at least three distinct superoxide dismutases, which can be visualized on polyacrylamide gel electropherograms of crude soluble extracts of the sonically disrupted cells. Of these, the slowest migrating and the fastest migrating, respectively, have previously been isolated and characterized as manganese-containing and iron-containing enzymes. The enzyme form with medium electrophoretic mobility has now been purified to homogeneity. Its molecular weight is approximately 37,000 and it contains 0.8 atoms of iron/molecule and only negligible amounts of manganese. Like other iron-containing superoxide dismutases and unlike the corresponding manganienzymes, it is inactivated by EDTA plus H2O2. Its specific activity is comparable to that of the other superoxide dismutases of E. coli. Two types of subunits could be distinguished upon electrophoresis in the presence of sodium dodecyl sulfate. One of these migrated identically with the subunit obtained from the manganisuperoxide dismutase, while the other similarly appeared identical with the subunit from the ferrisuperoxide dismutase. This newly isolated enzyme thus appears to be a hybrid of the other two forms. In support of this conclusion, we observed that ultrafiltration or storage of the new superoxide dismutase gave rise to the mangani- and ferrienzymes on disc gel electrophoresis or isoelectric focussing.

Avermectins, new family of potent anthelmintic agents: producing organism and fermentation.

The avermectins are a complex of chemically related agents which exhibit extraordinarily potent anthelmintic activity. They are produced by a novel species of actinomycete, NRRL 8165, which we have named Streptomyces avermitilis. The morphological and cultural characteristics which differentiate the producing organism from other species are described. The avermectins have been identified as a series of macrocyclic lactone derivatives which, in contrast to the macrolide or polyene antibiotics, lack significant antibacterial or antifungal activity. The avermectin complex is fully active against the gastrointestinal nematode Nematospiroides dubius when fed to infected mice for 6 days at 0.0002% of the diet. Fermentation development, including medium modification and strain selection, resulted in increasing the broth yields from 9 to 500 mug/ml.