Cryptococcus neoformans produces brown pigmented colonies when grown on agar media made from an extract of potatoes and carrots, broad beans (Vicia faba), or Guizotia abyssinica seeds. Since other yeasts do not produce the pigment, these media are useful as differential isolation media for C. neoformans. Similar specific pigment was produced by C. neoformans on chemically defined agar media which contained six different substrates of phenoloxidase (o-diphenol: oxygen oxidoreductase EC 1.10.3.1) an enzyme which catalyses the oxidation of o-diphenols to melanin. Substrates were incorporated singly into the media and included L-3,4-dihydroxyphenylalanine (L-DOPA), chlorogenic acid, protocatechuic acid, catechol, norepinephrine, and 3-hydroxytyramine hydrochloride (dopamine). No pigment was produced on media without substrate. Phenoloxidase activity in (NH,)2SO, precipitates of C. neoformans cell-free extract was assayed by measuring increases in absorbance at 480 nm produced in solutions of L-DOPA. This reaction showed oxygen uptake and was effectively inhibited by copper chelators, but not by catalase. The enzyme also oxidized the five other substrates which induced pigment formation. Electron micrographs of cells incubated in L-DOPA showed deposition of the pigment in the cell wall.

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A case of bursitis due to Prototheca wickerhamii is briefly reported. In histological sections the organism stained well with fungal stains, grey with silver methanamine and red with periodic acid Schiff reagent. This unicellular achlorophyllous alga was studied on common laboratory media. The characterization of the Prototheca sp. depends largely on wet mount microscopic examination from broth or agar cultures which ensures the observation of endosporulation and a consistent absence of budding. Otherwise the growth rate and the pasty white colonies may lead to an erroneous identification, most likely as a Cryptococcus sp. P. wickerhamii lends itself very well to standard physiological tests used for the identification of yeasts. The strain was found insensitive to 5-fluorocytosine. The MIC of amphotericin B was 0.15 microgram/ml.

Quantitative and qualitative studies were made of the fungi in the air over various parts of Canada and Alaska, continuing studies in arctic aerobiology. In winter, arctic air is apparently sterile: in summer, at Ft. Churchill, Man., ground level samples varied from 0.5 to 4.4 per cu. ft. Cladosporium was the commonest fungus (average 0.5 per cu. ft.), followed by yeasts (0.16), Penicillium (0.06), and Stemphylium (0.03 per cu. ft.). Other fungi present were Pullularia, Botrytis, Aspergillus, Verticillium, Pyrenochaete, Helminthosporium, Phyllosticta, Papularia, Cunninghamella, and Sporormia. Of 3711 colonies 57% failed to sporulate. Silicone slide readings as high as 114.9 fungus spores per cu. ft. were obtained and included the following: yeasts (8.6), Cladosporium (3.8), smuts (2.5), Fusarium (0.6), Alternaria (0.06 per cu. ft.), Venturia, Cercospora, Septoria, rusts, Leptosphaeria, Sordaria, and Pleospora and many hyaline one-celled spores. In two flights to Resolute Bay, N.W.T., the flora was found to be similar to that at Ft. Churchill but numbers did not exceed 1 per cu. ft., although readings up to 78 fungus spores per cu. ft. were recorded on slides in warm air over Hudson Bay. Most of the fungi are considered to be soil types originating in agricultural areas and carried northward by southerly winds. The majority are no longer viable when they reach the arctic. There is evidence that the numbers of fungi are correlated with air masses, not only in the arctic but also in air over other parts of Canada.