Nina Dabrowa

A survey of tide-washed coastal areas of southern California for fungi potentially pathogenic to man

Fungi pathogenic to man have seldom been isolated from marine habitats although oceans are known to contain a wide variety of different fungi. 1 Cryptococcus neo/ormans, ~ several species of Candida, 2, ~ and some opportImistic fungi 1 have occasionally been isolated from marine environments. The exact role of oceans as a possible source of fungi pathogenic to man, however, has received little attention. Ecologic studies have revealed the presence of pathogenic fungi in a variety of terrestrial environments. ~ The soil, particularly, has been recognized as a reservoir of those fungi responsible for most of the mycotic infections of man. 5-7 The ability to grow and reproduce under laboratory conditions on culture media containing sea water is one of the characteristics

Proline Uptake in Candida albicans

L-Proline entered both mycelial and yeast cells of Candida albicans by an active transport system of high specificity at low (less than 0.1 mM) external concentrations of substrate. The apparent Km value of this system was 0.1 mM for both types of cells, while the V value was 4 nmol min-1 (mg dry wt)-1 for mycelial cells and 1.4 nmol min-1 (mg dry wt)-1 for yeast cells. At L-proline concentrations greater than 0.1 mM, the amino acid appeared to enter both morphological forms by diffusion as well as active transport. As saturation was approached diffusion became increasingly important. The higher uptake rate of mycelial cells seemed not to be the result of an inducible system. The optimal pH and temperature for transport of L-proline were 7.0 and 37 degrees C, respectively. Sodium azide and the proline analogues sarcosine and L-azetidine-2-carboxylic acid inhibited L-proline uptake, while L-thiazolidine-4-carboxylic acid was less effective. The active transport system was highly specific for L-proline since neither ammonium ions, which inhibit the general amino acid transport system of fungi, nor 16 different amino acids interfered substantially with uptake.

Comparative disc electrophoretic studies of proteins from dermatophytes.

Human isolates of Microsporum gypseum, M. canis, Trichophyton mentagrophytes, T. tonsurans, T. rubrum and Epidermophyton floccosum were cultured in Sabourauds medium and Kuehns medium. The nondialyzable proteins of the culture filtrates and the mycelial mats were fractionated by disc electrophoresis. Characteristic electrophoretic patterns with 8 to 15 distinct protein fractions were obtained from each preparation. Comparisons among the species were made using the findings of each preparation from each medium. In each of the 4 comparisons a high number of homologous fractions was present in M. gypseum and M. canis and in T. mentagrophytes and T. tonsurans, and a high number of specific fractions was exclusively present in E. floccosum. These data are consistent with conventional taxonomic classification of the dermatophytes. Electrophoretic analysis of the dermatophytes may provide a new group of taxonomic characteristics complementing classical taxonomy.

Ethanol Tolerance and the Induction of Stress Proteins by Ethanol in Candida albicans

Ethanol is one of the products of the metabolism of glucose by Candida albicans. The amount produced is directly related to the concentration of glucose in the medium. The fungus utilizes ethanol as a sole source of carbon but is relatively intolerant of ethanol in its environment. Ethanol induces germ tube formation by blastoconidia of C. albicans. Germination was not seen under fermentation conditions even though the amount of ethanol produced was in the range form stress proteins that are similar to heat shock proteins. The possibility that stress proteins may regulate germ tube formation by C. albicans is discussed.

Comparative electrophoresis and numerical taxonomy of some Candida species

Protein extracts were prepared from six isolates of Candida albicans, three of C. stellatoidea, four of C. tropicalis, C. krusei and C. pseudotropicalis, and five of C. parapsilosis and C. guilliermondii. The 31 extracts were fractionated by disc electrophoresis using an anionic and a cationic system. Forty-six protein fractions were observed, including 27 different acidic fractions with the anionic system and 19 different basic fractions with the cationic system. Isolates of each species were identical or very similar in number and mobility of fractions. Interspecific differences were observed. Similarities among taxa were determined by numerical taxonomic methods. Isolates of each species, except C. albicans and C. stellatoidea, joined initially in a single cluster prior to linking interspecifically. Candida albicans and C. stellatoidea could not be separated by comparative disc electrophoresis.

Synthesis of nucleic acids and proteins in the dimorphic forms of Candida albicans

Candida albicans grown in tissue culture medium 199 buds when incubated at 25°C. but produces filaments when incubated at 37°C. Macromolecular synthesis by budding and filament producing blastospores of C. albicans grown at these 2 temperatures of incubation was studied. Cells incubated at 25°C. reproduced by budding with a generation time of 2 hr. The dry weight, protein and DNA increased 2-fold as the cells doubled in number while the RNA content of such cells increased about 3·2-fold. Ninety-five per cent of cells incubated at 37°C. produced filaments in 3 hr. A net increase in protein of 49% and in RNA of 94% was detected within the first 2 hr. of incubation at 37°C. By 4 hr. incubation protein had increased to 220% of the initial value and RNA to 300%. DNA content did not increase during the first 2 hr. of incubation but by 3 hr. the DNA content had increased to 50% of the initial value. Electrophoretic analysis of the water soluble proteins from budding and filament producing cells revealed that bot...

Disc electrophoretic studies of intraspecific variability of proteins from dermatophytes

Four different human isolates of Microsporum canis, Trichophyton mentagrophytes, T. rubrum, T. tonsurans and Epidermophyton floccosum were cultured for 14 days in Sabourauds medium at room temperature. The non-dialyzable proteins of the culture filtrates were fractionated by disc electrophoresis. The number and electrophoretic mobility of the protein fractions of the 4 isolates of each species were very similar. Interspecific electrophoretic differences, however, werepresent. Some variations in optical densities of homologous fractions were observed within each species. These data suggest that the qualitative electrophoretic patterns of these species are relatively stable taxonomic characteristics.

Phenotypic characteristics of a slow-growing, nongerminating variant of Candida albicans

Some of the phenotypic characteristics of a slow-growing, nongerminating variant of a commonly studied strain of Candida albicans are described. The variant arose as a chance isolate. The rate of occurrence was about 0 X 1% and the reversion rate was about 1 per 10(6) cells. The colony size was typically smaller than that of the parent and the yeast cells tended not to separate from one another so that catenulate strands of cells (pseudohyphae) were formed. Under standard conditions the generation time of the small-colony variant in liquid shake cultures was about twice that of the parental strain. Growth of the variant was suppressed by antimycin A, indicating that the small colony form was not the consequence of a defect in the cytochrome system. The colony size of the variant was not influenced by chlorobenzotriazole, which suggested that adenine metabolism was not involved in the small-colony phenotype. The pseudohyphal growth pattern was not relieved by high concentrations of utilizable carbohydrates, which means the catenulate microscopic appearance of the yeast cells was not simply an exaggeration of the normal growth pattern of isolates of C. albicans but more probably represented the growth of a cell-cycle mutant defective at the cell separation step. The cytoplasmic proteins of the variant and the parent were very similar though some unique peptides were displayed by each.

Nutritional stress proteins in Candida albicans.

Starving cells of Candida albicans synthesize at least seven proteins that represent nutritional-stress proteins (NSP). Such NSPs are formed by both germination-competent and germination-deficient strains of C. albicans. Heat-shock proteins (HSP) are not formed by starving cells. Germination-competent cells synthesize specific sets of proteins when incubated in a starvation medium that contains the germ-tube-inducing substances N-acetyl-D-glucosamine or L-proline. Both sets of induced proteins were also synthesized by a germination-deficient strain of C. albicans.

Generation Time of Candida albicans in Synchronized and Nonsynchronized Cultures

Synchronized growth of Candida albicans was induced. The generation time of the synchronized cells was compared with those of nonsynchronized cells cultured in Sabouraud broth, Medium 199, and a synthetic synchronization medium. The mean generation time of the synchronized cultures was 3·2 hours while that of the nonsynchronized cultures ranged from 1·7 to 3·6 hours. The generation time in shake cultures of nonsynchronized cells was uniformly shorter than that of the corresponding aerated cultures. The generation time in Sabouraud medium was the shortest and that in synthetic synchronization medium was the longest with each method of incubation.