Sophorose lipid production from lipidic precursors: Predictive evaluation of industrial substrates

Summary Sophorose lipids stand out as biosurfactants with a wide potential for industrial application and which can be produced in good yield from glucose and a lipidic cosubstrate.Candida bombicola CBS 6009 (ATCC 22214) was used in the present study. The influence of the lipidic cosubstrate on various aspects of production performance of these glycolipids (final concentration, yield) and on product composition (in particular, the structure of the hydroxy fatty acid vegetable and animal oils, markedly influenced product composition. In terms of production performance, the best substrates were oils or esters rich in C18:0 and C18:1 fatty acids. Optimal overall performance was obtained with esters (340 g L^–1 sophorose lipids with rapeseed esters). Conclusions drawn from the results allow predictive evaluation of lipidic industrial substrates.     

细叶黄芪叶肉原生质体发育早期几种细胞器的变化

在细叶黄芪叶肉原生质体发育早期,细胞器的变化较大。离体培养4h后,线粒体的嵴和基质物质开始增加。培养3—5天后,线粒体的数量增加5倍以上,此时可见大部分线粒体围绕细胞核分布。在培养24h后,高尔基体开始发育,它们主要分布在细胞质周边区域。多糖细胞化学染色表明,高尔基体内沉积着大量嗜银物质。培养1天后,粗面内质网开始发育。培养3天时,部分叶绿体边缘出现一些空隙结构。随着叶绿体内膜结构的消失,淀粉粒增大,叶绿体逐渐转变为造粉质体。     

In vitro susceptibility ofPityrosporum ovale (Malassezia furfur) to human androgenic steroids

Cells ofPityrosporum ovale that colonize human pilosebaceous units are constantly exposed to cutaneous androgenic steroids. The aim of our study was to find out whetherP. ovale is susceptible to these hormones. Three strains ofP. ovale were grown in vitro in the presence of various concentrations oftestosterone, dehydroepiandrosterone, androstenedione, androstanedione, 5--dihydrotestosterone andprogesterone (10, 100, and 1000 µg/ml; agar dilution assays). In addition, three strains ofCandida albicans were also exposed to equal concentrations of the same androgens. As a result, allP. ovale strains were suppressed by 1000 µg/mlandrostenedione, which was the strongest inhibitor. The other androgenic steroids also significantly reducedP. ovale growth at different concentrations, depending on the hormone used and the strain tested.Progesterone was inhibitory at the highest concentration for oneP. ovale strain only.Candida albicans was not affected by any of the androgens. These findings demonstrate an in vitro susceptibility ofP. ovale to high concentrations of human androgenic steroids. A relevance of this interaction for the in vivo fungus-host relation is not apparent.     

Effect of glucose starvation on germ-tube production byCandida albicans

By incubating starved and unstarved yeast cells in synthetic media with a pH of 4.5 or 6.7 at 37°C the effect of a 3 hours' glucose starvation on germ-tube production byCandida albicans was evaluated. In addition the endocellular content of total carbohydrates, glycogen, trehalose and proteins after and before the starvation were dosed. The most interesting result was the overcoming of the pH-regulated dimorphism, thanks to the starvation treatment. Infact the starved cultures produced germtubes indifferently in neutral or acid media, whereas the filamentation of the unstarved cultures was more copious in pH 6.7 medium. The endocellular content of trehalose and protein was unchanged, whereas total carbohydrates and glycogen showed a shortage after the 3 hours' glucose starvation. The possible involvements of these metabolic changes in the regulation of dimorphic transition are discussed.     

The kinetics and regulation of M-xylose transport in Candida utilis

Low-affinity (K _m=67.6±3.2 mM) and high-affinity (K _m=1.9±1.2 mM) D-xylose transport occur in Candida utilis grown, respectively, on D-glucose or D-xylose. Starvation of glucose-grown cells decreases the K _m value (10.5±2.6 mm). The high-affinity system appearing during starvation required protein synthesis and it was inactivated when cells were exposed to glucose, by a process independent of protein synthesis. High-affinity transport was accompanied by transient alkalinization of yeast suspensions, indicating that it is a proton symport, whereas low-affinity transport was not. Both systems, however, were inhibited by metabolic inhibitors and by replacing H₂O in the transport assay with D₂O, indicating that both may be proton symports. Glucose and acetic acid also inhibited both high-and low-affinity xylose transport.S.G. Kilian, B.A. Prior and J.C. du Preez are with the Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, Bloemfontein 9300, Republic of South Africa     

Antibiofilm Activity of Invasive Plants against Candida albicans: Focus on Baccharis halimifolia Essential Oil and Its Compounds

The extracts of five invasive plants were investigated for antifungal and antibiofilm activities against Candida albicans, C. glabrata, C. krusei, and C. parapsilosis. The antifungal activity was evaluated using the microdilution assay and the antibiofilm effect by measurement of the metabolic activity. Ethanol and ethanol-water extracts of Reynoutria japonica leaves inhibited 50 % of planktonic cells at 250 μg mL⁻¹ and 15.6 μg mL⁻¹, respectively. Ethanol and ethanol-water extracts of Baccharis halimifolia inhibited >75 % of the mature biofilm of C. albicans at 500 μg mL⁻¹. The essential oil (EO) of B. halimifolia leaves was the most active (50 % inhibition (IC₅₀) at 4 and 74 μg mL⁻¹against the maturation phase and 24 h old-biofilms of C. albicans, respectively). Oxygenated sesquiterpenes were the primary contents in this EO (62.02 %), with β-caryophyllene oxide as the major component (37 %). Aromadendrene oxide-(2), β-caryophyllene oxide, and (±)-β-pinene displayed significant activities against the maturation phase (IC₅₀=9–310 μ mol l⁻¹) and preformed 24 h-biofilm (IC₅₀=38–630 μ mol l⁻¹) of C. albicans with very low cytotoxicity for the first two compounds. C. albicans remained the most susceptible species to this EO and its components. This study highlighted for the first time the antibiofilm potential of B. halimifolia, its EO and some of its components.     

Complex interaction between different proteinaceous components within the cell-wall structure ofCandida albicans

We have previously described a monoclonal antibody, MAb DC3:H10, which recognized an epitope preferentially expressed on the surface ofCandida albicans germ tubes. In the present study we examined the MAb-reactive material further. Immunoblot analysis of the material purified partially by Sephadex G-200 and DEAE-Sephacel chromatography reacted with antibodies to theC. albicans C3d receptor (CR2). In an ELISA, MAb DC3:H10 captured antigen that was recognized by both anti-CR2 and anti-mp58 fibrinogen binding mannoprotein polyclonal antibodies. The MAb DC3:H10 failed to compete with either of these antisera in an ELISA. Indirect immunofluo-rescence (IIF) analysis showed differences in surface distribution for the MAb DC3:H10, the CR2, and the mp 58 epitopes. Dual labeling IIF experiments showed MAb DC3:H10 binding to be unaffected by binding of fibrinogen or anti-mp58 antibody. However, the binding patterns of MAb DC3:H10 were modified in the presence of anti-CR2 antibody, suggesting a complex interaction between these cell wall components.     

Elimination of the yeastCandida parapsilosis from lymphoid cells and monolayer cells in culture

Summary In our laboratory, airborne yeast contaminants of cell cultures have consistently been of the genusCandida (speciesCandida parapsilosis), which are difficult to control with fungicidal agents. To salvage cell lines that show the presence of this fungus, two effective methods may be employed. In early stages of infection, the addition of activated mouse peritoneal macrophages (5×10⁵ cells/ml) to the culture medium containing 5 μg Fungizone/ml eliminates all spores by phagocytosis. More heavily contaminated cultures can be depleted of fungi by density centrifugation on a layer of 38% Percoll. Remaining single spores, often not detectable by light microscopy, can be removed by the addition of macrophages (2×10⁵/ml) and Fungizone (5 μg/ml) to the culture medium. Contaminated monolayer cells can be freed of blastospores by several washes with balanced salt solution and subsequent culturing for 4 d in medium containing 10 μg Fungizone/ml without any toxic effects to the cells. These procedures can rescue valuable cell lines and hybridomas that would otherwise be lost. This work was supported by Veterans Administration Research Funds.