The ultrastructure of Candida krusei

Various methods of chemical fixation and freeze-drying of Candida krusei were compared to determine the most appropriate method for the ultrastructural investigation of the thick walled organisms of this genus. Freeze-drying without chemical fixation was of little value because of insufficient variation in electron density. Potassium permanganate was able to penetrate the intact cell but failed to show cytoplasmic glycogen and lipid and some details of the cell wall. While normal glutaraldehyde, formaldehyde and osmium tetroxide treatment failed to permeate and preserve intracellular structures, several cycles of rapid freezing (–155°C) and thawing followed by glutaraldehyde fixation and osmium tetroxide post-fixation demonstrated the intracellular details of the majority of cells so treated.     

Candida krusei in Baker's yeast production

Summary Candida krusei is a harmful contaminant in baker's yeast manufacture, because it grows much faster than Saccharomyces cerevisiae under production conditions. This investigation showed that C. krusei utilizes the ethanol produced by baker's yeast as sole carbon source when molasses is used as a substrate. When the alcohol concentration in the effluent air is used as a parameter for controlling the aeration of the culture, conditions become favourable for the dominance of wild yeast because some of the ethanol produced by the baker's yeast is consumed immediately by C. krusei and aeration is then automatically reduced, leading to increased growth of the wild yeast.     

Metergoline-induced cell death in Candida krusei

Metergoline possesses potent antifungal activity against Candida krusei, a notorious yeast species that is inherently resistant to the common antifungal agents. In an attempt to elucidate the action mechanisms of metergoline, the present study was designed to investigate its effects on a number of classical markers of apoptosis in C. krusei. The results showed that transient exposure (2h) to metergoline led to a massive intracellular accumulation of reactive oxygen species (ROS) and depolarization of mitochondrial membrane potential in a concentration-dependent fashion. Analyses of the treated fungal cells after prolonged incubation (12h) with metergoline by flow cytometry and fluorescence microscopy clearly demonstrated phosphatidylserine externalization, the presence of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling-positive cells and fungal cells undergoing necrosis. Taken together, our data provide evidence that metergoline elicited cell death process in C. krusei through elevation of the intracellular ROS level and perturbation of mitochondrial homeostasis, followed by damage of nucleus and eventual cell demise.     

Candida krusei in genital infections]

Frequency of appearance of Candida krusei in human reproductive tract, susceptibility of these microorganisms to drugs and their importance in pathogenesis of mycosis, were investigated. Strains C. krusei species constituted 6.7% of the total 1325 strains and 21.8% within other than C. albicans species yeast-like fungi. Vaginal mycosis caused by fungi from C. krusei species occurs in presence of Lactobacillus sp. and correct values of pH in vaginal contents, however changed leukocytosis in evident. Over 60% of patients with C. krusei infection were complaining that they feel disturbances within the reproductive tract. Investigation of susceptibility of C. krusei to drugs revealed highest activity of cotrimazine and pimaricin.     

不同渗透压调节剂对Candida krusei生理代谢的影响

比较了氯化钠、氯化钾、甘露醇存在的高渗环境下克鲁氏假丝酵母(Candida kru-sei)的生理代谢。3种渗透压调节剂对C.krusei生理代谢影响有显著差异。与甘露醇相比,氯化钠和氯化钾对细胞生长的影响更为显著,而氯化钾对细胞的毒性则又小于氯化钠。细胞对糖的消耗速率依次为甘露醇>氯化钾>氯化钠。甘油和海藻糖是C.krusei在高渗环境下的主要相容性溶质。氯化钠和氯化钾对甘油合成的促进作用明显高于甘露醇。在0.6mol/L氯化钠、氯化钾、甘露醇存在时,细胞甘油浓度较对照提高了74%、63%、57%;胞内甘油最大含量也分别达到对照的3.1,2.4和1.8倍。高渗环境下胞内海藻糖含量在发酵前期均有所降低,但发酵后期在0.6mol/L氯化钾和甘露醇存在时海藻糖迅速积累,其含量分别达对照的1.6和1.4倍。     

链格孢霉合并克柔念珠菌所致肺部感染1例

1临床资料患儿,男,10岁,于2009年6月25日入住我院小儿科。9d前无明显诱因出现发热、咳嗽（当日外周血白细胞11．5×10^9／L,中性粒细胞72．4％）,在外院抗感染治疗无效,并伴胸闷、气短、心悸转入我院。入院查体,呼吸音粗,双肺可闻及少许细湿罗音和干罗音,伴少许喘鸣音;胸片可见双肺斑片状影,边界不清,呈“蝴蝶翼”样,     

地黄属分子系统学分析

地黄属是中国准特有属,属内种间关系仍待澄清。该研究基于多个个体的叶绿体与核基因片段对地黄属进行系统发育重建,探讨属内物种分化与可能历史。结果表明:(1)地黄属为单系群,天目地黄为本属原始类群,并与湖北地黄互为姐妹群或连续姐妹群,裂叶地黄-高地黄、地黄-茄叶地黄分别组成姐妹群;(2)多个个体构建的系统树更能揭示本属物种关系的复杂性;(3)祖先分布区重建表明本属经历过3次扩张与2次隔离过程,物种形成过程与历史气候变化密切相关。最后该研究提出了地黄属物种形成研究亟待解决的几个重要问题。     

Candida krusei : biotechnological potentials and concerns about its safety

Yeasts have a tradition in biotechnological applications, and Saccharomyces species are the most dominating representatives. Among the yeast species, Candida krusei has been isolated from different habitats, and in recent years, it has gained increased interest because of its diverse biotechnological role. It is found in many fermented food items and dairy products and has also been exploited for production of biochemicals and enzymes. However, because of its opportunistic pathogenic nature, it draws scientific attention regarding the safety of its industrial exploitation. Candida?krusei generally causes infections in immunocompromised patients, such as those suffering from Human immunodeficiency virus - acquired immune deficiency syndrome, and also in cancer patients. The recent increase in the use of immunosuppressive drugs has increased the chances of C.?krusei infections. Candida?krusei possesses an intrinsic resistance to many triazole antifungal drugs, especially fluconazole, which is a main drug used in antifungal therapy; therefore, there is serious concern regarding its safe industrial use.     

Temperature effects on ethanol and isopropanol utilization by Candida krusei

Candida Krusei has a optimum growth temperature of 37°C on SASOL ethanol-isopropanol mixture. The organism was unable to grow on isopropanol, but oxidized it partially to acetone in the presence and absence of ethanol. Growth at 40°C in the alcohol mixture was slightly faster than at 30°C over an ethanol concentration range of 0.43 to 3.6% (v/v), although at both temperatures the growth rate declined continuously with increasing concentration. At an ethanol concentration greater than 3.6% (v/v), the mixture was much more inhibitory to growth at 40 and 30°C. The inhibitory effect was due to the ethanol rather than the isopropanol. Metabolites such as acetate, acetaldehyde, and ethyl acetate accumulated in the medium, but the degree of accumulation depended upon the temperature and alcohol mixture concentration. At 40°C, acetaldehyde and acetate accumulated to a greater extent than 30°C on a 4.0% (v/v) synthetic alcohol mixture and this may also cause the greater inhibition at this temperature. The alcohol mixture is unsuitable for single cell protein (SCP) production in batch culture because of the low cell densities observed at all alcohol concentrations.     

Antifungal Activity of Baicalein Against Candida krusei Does Not Involve Apoptosis

The present study was designed to evaluate the antifungal activity of baicalein against Candida krusei isolates. Using a broth microdilution assay, baicalein exhibited potent in vitro antifungal activity against C. krusei isolates with a minimum inhibitory concentration of 2.7 μg/ml. Flow cytometric study indicated that baicalein depolarized mitochondrial membrane potential in a concentration-dependent manner. However, mechanistic analyses showed that the intracellular reactive oxygen species (ROS) level was virtually unchanged, and massive DNA fragmentation was not observed in C. krusei isolates after baicalein treatment even at a concentration which was apoptotic in C. albicans. Taken together, we conclude that the antifungal activity of baicalein in C. krusei isolates occurs through perturbation in mitochondrial homeostasis without causing elevation of the intracellular ROS level and does not involve apoptosis.     

中国主栽樱花的分子系统发育分析

以88份樱花为试验材料,利用核基因ITS和叶绿体间隔序列trnH-psbA进行测序,经过软件MEGA 6.0处理后,构建了系统发育树。结果表明,山樱群樱花品种系统发育比较混乱,这与其遗传背景比较复杂以及原始亲本系统发育关系较近有关,江户彼岸群和寒绯樱群的大多数品种能够聚类在一起,与山樱群品种能分得开,但涉及到很多杂交品种,ITS和trnH-psbA难以区分,表明DNA条形码技术难以应用到杂交品种的系统发育关系,此外,还可依据某些樱花品种特异的ITS或trnH-psbA序列长度对部分品种进行分子鉴定,也对部分种系不明的品种进行了修订。     

Molecular Characterization and Phylogenetic Analysis of Hoplolaimus stephanus

Three Hoplolaimus stephanus populations were characterized morphologically, both by morphometrics and by SEM observations. These populations were used to develop a rapid and accurate molecular identification method for the species, which is useful because of the high level of morphological similarity between H. stephanus and H. galeatus. Species-specific primers for H. stephanus, amplifying a distinct fragment (260 bp) of the nuclear ribosomal internal transcribed spacer1 (ITS1), can be used in multiplex PCR along with previously developed primers for other common Hoplolaimus species. We also infer phylogenetic relationships among H. stephanus, the closely-related H. galeatus, and several other Hoplolaimus species, using sequences of the actin gene, ITS1 and LSUD.     

Novel fermentation strategy for enhancing glycerol production by Candida krusei

During the later stage of glycerol production by fermentation of Candida krusei, glycerol consumption by the strain was observed, although there was residual sugar in the medium. To enhance the final glycerol accumulation, a new fermentation strategy was developed by maintaining high activities of glycerol synthetic enzymes (i.e., glycerol-3-phosphate dehydrogenase (ctGPD) and glycerol-3-phosphatase (GPP)) for a relatively long period while conducting oxygen limitation at a later stage to inhibit the increase of another enzyme activity related to glycerol degradation (i.e., mitochondrial glycerol-3-phosphate dehydrogenase (mtGPD)). With oxygen limitation performed from 88 h, when ctGPD and GPP activities were already at a low level while mtGPD activity was increasing, the glycerol dissimilation was efficiently reduced. The final glycerol concentration reached 55.6 g/L, which was about 18% (96 h) and 30% (104 h) higher than control, and its productivity increased to 0.54 g/(L h). The proposed strategy based on cell physiology was proved useful to the glycerol fermentation process.     

Effect of dietary carbohydrates on the in vitro epithelial adhesion of Candida albicans, Candida tropicalis, and Candida krusei

Adhesion to epithelial surfaces is considered as a critical step in the pathogenesis of oral candidosis. Therefore, the effects of the most commonly consumed dietary carbohydrates on the adhesion of Candida albicans, Candida tropicalis, and Candida krusei to monolayered HeLa cells were investigated. Adherence of C. albicans and C. tropicalis appeared significantly promoted by incubation in defined medium containing a high concentration (500 mM) of fructose, glucose, maltose, and sucrose (p < 0.001). C. albicans organisms grown in sucrose elicited maximal increase in adhesion, whereas adhesion of C. tropicalis and C. krusei was enhanced to the greatest extent when cultured in glucose. Maltose and fructose also promoted adherence of C. albicans and C. tropicalis (p < 0.001), but to a lesser extent than sucrose and glucose. On the other hand, sorbitol-grown yeasts demonstrated a marginal increase in adhesion (p > 0.01). Xylitol only significantly reduced adherence of C. albicans (p < 0.001). These results suggest that the frequent consumption of carbohydrates, such as sucrose, glucose, maltose, or fructose, might represent a risk factor for oral candidosis. The limitation of their consumption by substituting xylitol or sorbitol could be of value in the control of oral Candida colonization and infection.     

Sterol content and polyene antibiotic resistance in isolates of Candida krusei, Candida parakrusei, and Candida tropicalis.

Three isolates, one from each species of Candida krusei, C. parakrusei, and C. tropicalis, obtained from infected patients, were more tolerant of significantly higher concentrations of polyene antibiotics than the corresponding reference wild types. The resistant strains isolated had the same sterols as their wild-type counterparts but in lower concentrations.