Interspecific complementation analysis by protoplast fusion of Candida tropicalis and Candida albicans adenine auxotrophs.

A protocol employing inositol starvation was used to isolate proline and adenine auxotrophs of Candida tropicalis. Interspecific hybrids between red adenine auxotrophs of C. tropicalis and Candida albicans were formed by protoplast fusion. These C. tropicalis red adenine auxotrophs were shown to fall into two complementation groups by crossing them with a known C. albicans ade1 tester strain. It is suggested that these two groups correspond to the ade1 and ade2 mutants of Saccharomyces cerevisiae and C. albicans and that these defined mutants may be useful in attempts to develop transformation systems for C. tropicalis.     

Effect of ethyl methane sulphonate on biomass and protein production by Candida tropicalis

Large doses of ethyl methanesulphonate (EMS) greatly increased the induction of auxotrophic mutants in Candida tropicalis. The maximum yield of biomass and protein was recorded in some mutants isolated after treatment with 60, 80 and 100 ppm EMS. The electrophoretic protein profile revealed typical banding patterns for both C. tropicalis wild type and mutants.     

Strain improvement of Candida tropicalis for the production of xylitol: biochemical and physiological characterization of wild-type and mutant strain CT-OMV5

Candida tropicalis was treated with ultraviolet (UV) rays, and the mutants obtained were screened for xylitol production. One of the mutants, the UV1 produced 0.81 g of xylitol per gram of xylose. This was further mutated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and the mutants obtained were screened for xylitol production. One of the mutants (CT-OMV5) produced 0.85 g/g of xylitol from xylose. Xylitol production improved to 0.87 g/g of xylose with this strain when the production medium was supplemented with urea. The CT-OMV5 mutant strain differs by 12 tests when compared to the wild-type Candida tropicalis strain. The XR activity was higher in mutant CT-OMV5. The distinct difference between the mutant and wild-type strain is the presence of numerous chlamydospores in the mutant. In this investigation, we have demonstrated that mutagenesis was successful in generating a superior xylitol-producing strain, CT-OMV5, and uncovered distinctive biochemical and physiological characteristics of the wild-type and mutant strain, CT-OMV5.     

Isolation of Candida tropicalis auxotrophic mutants

An enrichment scheme using nystatin was designed for the isolation of auxotrophic mutants from the diploid-alkane-utilizing yeast Candida tropicalis. A collection of 194 auxotrophs representing 7 phenotypes was isolated. One class of mutants was identified as having a defect in histidinol dehydrogenase activity and a second class of mutants was identified as having a defect in orotidine monophosphate decarboxylase activity. These strains are good candidates to be carrying mutations corresponding to the HIS4 and URA3 genes of Saccharomyces cerevisiae.     

Alcohol-conferred hemolysis in yeast is a consequence of increased respiratory burden

We have previously reported that growth on alcohol vapors confers hemolytic properties on certain yeast species and strains ('microbial alcohol conferred hemolysis'; MACH). Here, a Saccharomyces cerevisiae deletion library consisting of c. 4800 clones was screened for MACH mutants in the presence of n-butanol vapors; 136 mutants were MACH-negative, and 325 exhibited reduced hemolysis and/or growth. Of the MACH-negative mutants, 35.3% were affected in mitochondrial-related genes. The data suggest that intact mitochondrial and respiratory chain functions are critical for the observed MACH phenomenon. We propose that the uncontrolled cellular uptake of alcohol results in yeast 'hyper-respiration', leading to elaboration of hemolytic molecules such as hydrogen peroxide and hemolysis-causing lipids. To support this premise, we showed that: (1) exogenous catalase and glutathione reduce alcohol-conferred hemolysis in S. cerevisiae BY4741 and Candida tropicalis 59445; (2) C. tropicalis produces hydrogen peroxide following growth on ethanol and n-butanol, as shown using xylenol orange; and (3) a lysophospholipid-containing lipid extract from alcohol-grown C. tropicalis specifically causes hemolysis.     

热带念珠菌引起唇部念珠菌性肉芽肿1例

报告1例由热带念珠菌引起的唇部感染。患者女,22岁,下唇部斑块1 a。皮损组织病理学检查及真菌培养见热带念珠菌生长。给予伊曲康唑200 mg/d口服等治疗1个月后皮损完全消失。     

Characteristics of Candida tropicalis D-2 mutants resistant to nystatin, levorin, amphotericin B. I. Frequency of induction depending on the intracellular lipid level and phenotypic characteristics of mutants

Induction frequency of mutants of Candida tropicalis D-2 strain depends on the number of intracellular lipids and the nature of a chemical mutagen. Para-aminobenzoic acid leads to a decrease in the lethality and mutagenicity of nitrosocompounds, which is stronger expressed in cells with enhanced quantity of lipids. Among nystatin and levorin-resistant mutants obtained independently, the mutants with supersensitivity to other antibiotics were discovered. The majority of mutants possess cross-resistance.     

Isolation and enzyme determination of Candida tropicalis mutants for DCA production

Techniques, named two-step enrichment and double-time replica-plating method (TEDR), are described that allow a mutated population of Candida tropicalis to be enriched efficiently for mutants deficient in the alkane degradation pathway (Alk(-)) and to be selected easily for mutants increasing in the DCA (dicarboxylic acids) excretion pathway. After C. tropicalis was mutated with ethyl methane sulphonate and ultraviolet, the Alk(-) mutants were enriched (the first step enrichment, up to eightfold in one round of enrichment) by treatment with nystatin in medium SEL1-1. The mutagen-treated cells were then cultured in medium YPD containing chlorpromazine for further enriching (the second-step enrichment, up to threefold in one round) the mutants with an increasing capacity of alpha- and omega-oxidation. On the other hand, the Alk(-) mutants were readily isolated by the SEL1 replica-plating method by using alkane or glucose as the sole carbon source. A total of 43 Alk(-) mutants were isolated from 2x10(8) mutagen-treated cells. In the following steps, by using SEL2 replica plating, the screening studies showed that of the 43 Alk(-) mutants, 11 strains could accumulate DCA greatly from alkane, and strains 1-12 and 1-3, especially, could produce nearly three times as much DCA as the wild-type organism could. The results showed that the strains had more cytochrome P450 activity and a higher converting capacity of alkane.     

Detection of specificity of a new antigen in Candida tropicalis and its evaluation by taxonomic DNA analyses

Monospecific factor serum for identifying Candida tropicalis was obtained either from rabbit antiserum to heated cells of C. tropicalis M 1519 (S 96) or from antiserum to C. tropicalis IFO 1400, by adsorption with heated cells of Candida albicans serotype A, or C. albicans (A) and Candida krusei, respectively. We designated this adsorbed serum factor t serum. The monospecific factor serum reacted with 31 out of 32 strains of C. tropicalis, only when tested on heat-treated cell antigens, whereas it did not react with any of 72 strains of the six other medically important species of Candida. The morphological and physiological characteristics of the one strain of C. tropicalis that did not react with the factor t serum, designated the t- -strain, were shown to be similar to those of the type strain of C. tropicalis by most of the methods employed for identifying Candida. Therefore, cell wall mannan from the t- -strain was compared with that from several typical strains of C. tropicalis for its specificity by the precipitation reaction and also for its 1H-nuclear magnetic resonance spectrum. The results showed that these mannans are similar to each other serologically and physicochemically, suggesting that the new antigen t is not mannan. Taxonomic characterization of the t-- and several typical strains of C. tropicalis was carried out by determining the mol% G+C of their DNA and also their DNA homology. Although the mol% G+C values of four typical strains of C. tropicalis were fairly similar (35.2 to 36.2 mol% by the Tm method and 35.5 to 36.4 mol% by the HPLC method), the t- -strain had a G+C content of 44.1 (Tm) and 43.3 (HPLC) mol%. Furthermore, the DNAs of the t- -strain and the type strain of C. tropicalis showed only 18.2% relatedness. These results suggest that the antigen corresponding to serum factor t exists only in the cell wall of C. tropicalis strains, not in those of the other medically important Candida, and that the t- -strain should not be classified as C. tropicalis. In conclusion, the taxonomic value and usefulness of factor t serum is primarily for differentiating C. tropicalis from C. albicans serotype A serologically.     

Interspecific hybridisation between Candida albicans and Candida tropicalis

Abstract Protoplasts from auxotrophic mutants of Candida albicans and Candida tropicalis were produced by snail enzyme treatment and their fusion was induced with polyethylene glycol (PEG). During selective regeneration, nutritionally complemented interspecific hybrids were obtained. Their cells contained one nucleus, and the DNA content per cell was higher than in the parents. The isoenzymic and sugar assimilation patterns of the mutants, and those of the hybrids and the products after their haploidisation, were also analysed. The results indicated that the hybrids were partial alloploids containing the total chromosomal set of either of the parental species and one or a few chromosomes of the other.