Life‐history parameters and predation capacity of Macrolophus pygmaeus and Nesidiocoris tenuis (Hemiptera: Miridae) on eggs of Plutella xylostella (Lepidoptera: Plutellidae)

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Variations in yeast plasma‐membrane lipid composition affect killing activity of three families of insect antifungal peptides

Naturally occurring antimicrobial peptides and their synthetic analogues are promising candidates for new antifungal drugs. We focused on three groups of peptides isolated from the venom of bees and their synthetic analogues (lasioglossins, halictines and hylanines), which all rapidly permeabilised the plasma membrane. We compared peptides' potency against six pathogenic Candida species (C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. krusei and C. dubliniensis) and the non‐pathogenic model yeast Saccharomyces cerevisiae. Their activity was independent of the presence of the multidrug‐resistant pumps of C. glabrata but was influenced by the lipid composition of cell plasma membranes. Although the direct interaction of the peptides with ergosterol was negligible in comparison with amphotericin B, the diminished ergosterol content after terbinafine pretreatment resulted in an increased resistance of C. glabrata to the peptides. The tested peptides strongly interacted with phosphatidylglycerol, phosphatidic acid and cardiolipin and partly with phosphatidylinositol and phosphatidylethanolamine. The interactions between predominantly anionic phospholipids and cationic peptides indicated a mainly electrostatic binding of peptides to the membranes. The results obtained also pointed to a considerable role of the components of lipid rafts (composed from sphingolipids and ergosterol) in the interaction of yeast cells with the peptides.     

香叶挥发油成分分析及其对 小鼠白色假丝酵母菌阴道病的影响

目的 研究香叶挥发油对白色假丝酵母生物膜形成的影响。方法 水蒸气蒸馏法提取香叶挥发油,GC-MS分析其成分,测定其对白色假丝酵母的MIC、MBC,激光共聚焦显微镜下观察白色假丝酵母生物膜的形成,制备小鼠白色假丝酵母菌阴道病模型,观察香叶油治疗效果。结果 香叶挥发油提取率为1.83%,分析出22个成分,主要成分为5-甲基-2-异丙烯基环己酮、3,7-二甲基-2-辛烯-1-醇、(顺)香叶醇、异香叶醇、香叶醇和甲酸香茅酯,MIC值为0.3625%,MBC值为0.6250%,激光共聚焦结果显示不同浓度香叶油均可显著抑制白色假丝酵母生物膜形成,动物实验结果显示香叶油可抑制小鼠阴道炎症改变。结论 香叶油用于治疗白色假丝酵母引起的阴道炎机制可能与其影响细菌生物膜形成有关。     

米卡芬净对分离自中国的念珠菌和曲霉临床株体外抑菌活性的研究

目的了解新型抗真菌药物米卡芬净(micafungin,MFG)对分离自中国的念珠菌和曲霉临床株的体外抑菌活性。方法参照CLSI(Clinical and Laboratory Standards Institute,以前为NCCLS)制定的M27-A2和M38-A方案测定86株念珠菌和35株曲霉的最低抑菌浓度(MIC)或最低有效浓度(MEC)。结果MFG对大多数念珠菌属和曲霉属均有较好的抑菌作用。对念珠菌属的MIC90从高到低依次为:氟康唑(FLC)敏感的白念珠菌、热带念珠菌、光滑念珠菌为0.125μg/ml,FLC耐药和剂量依赖敏感株为0.25μg/ml,克柔念珠菌为0.5μg/ml,近平滑念珠菌8μg/ml,季也蒙念珠菌>16μg/ml。MFG对烟曲霉的MEC90为≤0.03μg/ml,对非烟曲霉的曲霉属MEC90为0.06μg/ml。MFG与唑类药物、两性霉素B(AMB)不存在交叉耐药,对FLC耐药的念珠菌、伊曲康唑耐药的曲霉、AMB不敏感的曲霉均有好的抑菌活性。结论MFG对多数念珠菌属和曲霉属(包括对唑类耐药和AMB不敏感的菌株)有较好的体外抑菌作用。     

The strange case of a biofilm-forming strain of Pichia fermentans, which controls Monilinia brown rot on apple but is pathogenic on peach fruit

A biofilm-forming strain of Pichia fermentans proved to be most effective in controlling brown rot on apple fruit when coinoculated into artificial wounds with a phytopathogenic isolate of Monilinia fructicola. Culture filtrates and autoclaved cells had no significant influence on the disease. When sprayed onto the apple fruit surface, this yeast formed a thin biofilm but failed to colonize the underlying tissues. When inoculated into wounds artificially inflicted to peach fruit or when sprayed onto the surface of peach fruit, the same strain showed an unexpected pathogenic behaviour, causing rapid decay of fruit tissues even in the absence of M. fructicola. Both optical and scanning electron microscopy were used to evaluate the pattern of fruit tissue colonization by P. fermentans. While on apple surface and within the apple wound the antagonist retained its yeast-like shape, colonization of peach fruit tissue was always characterized by a transition from budding growth to pseudohyphal growth. These results suggest that pseudohyphal growth plays a major role in governing the potential pathogenicity of P. fermentans, further emphasizing the importance of a thorough risk assessment for the safe use of any novel biocontrol agent.     

Identification and characterization of a functional Candida albicans homolog of the Saccharomyces cerevisiae TCO89 gene

As one of the components of target of rapamycin complex 1 (TORC1), ScTco89p is involved in rapamycin sensitivity and cellular integrity in Saccharomyces cerevisiae. Here we provide evidence showing that deletion of ScTCO89 causes yeast cells to be hypersensitive to salt stress in a high osmolarity glycerol pathway-independent fashion. In addition, we have identified and characterized a functional Candida albicans homolog (CaTCO89) of ScTCO89, which encodes a protein of 708 amino acids that shows overall 15% identity with ScTco89p at the amino acid level. However, CaTCO89 could complement the functions of ScTCO89 in rapamycin sensitivity, salt tolerance, and cellular integrity. Candida albicans cells disrupted for CaTCO89 are also sensitive to rapamycin and lithium salt, but not susceptible to challenges to cellular integrity.