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碳源对玫烟色虫草菌丝生长、芽生孢子产生及其耐热性的影响
({{custom_author.role_cn}}), {{javascript:window.custom_author_cn_index++;}}Effects of carbon sources on mycelial growth, blastospore production and thermotolerance of Cordyceps fumosorosea
({{custom_author.role_en}}), {{javascript:window.custom_author_en_index++;}}提高虫生真菌孢子应对热胁迫的能力是生防菌应用研究的关键,为研究菌丝培养阶段碳源对玫烟色虫草Cordyceps fumosorosea IF-1106耐热性的影响,选择了麦芽糖、可溶性淀粉、蔗糖、葡萄糖、果糖、海藻糖为碳源的培养基对玫烟色虫草IF-1106进行液体培养,评估了不同碳源条件下菌丝的生长、产孢及所产芽生孢子的耐热性。结果表明,在菌株培养阶段,培养基中碳源的种类及浓度对菌丝产量、产孢量及所产芽生孢子的耐热性有显著影响,其中蔗糖为碳源时,所产芽生孢子的耐热性强,45 ℃热胁迫条件下LT50为1.65 h;蔗糖浓度为40 g/L时,可产生大量耐热芽生孢子,液体培养3 d后产孢量可达3.43×107个孢子/mL。为探索不同培养条件下所产芽生孢子耐热性不同的原因,提取了孢子内的海藻糖并采用离子色谱法对其进行了定量分析,发现耐热性高的芽生孢子胞内海藻糖含量普遍较低,可见海藻糖是与芽生孢子耐热性密切相关的内源物质。综上所述,选择适宜的培养基是调控孢子耐热性的有效途径,本研究为生产高耐热的玫烟色虫草生防制剂提供了有益的指导。
Improving the ability of resistance of entomogenous fungal spores to heat stress is critical for effectiveness of biocontrol. The effect of carbon sources on the growth, blastopore production and thermotolerance of Cordyceps fumosorosea IF-1106 was investigated. Maltose, soluble starch, sucrose, glucose, and fructose were selected as carbon sources, and the mycelial growth, sporulation and thermotolerance of the produced blastospores were evaluated under liquid cultures condition. The results show that the mycelial yield, sporulation and thermotolerance of blastospores are significantly impacted by different carbon sources at different concentrations in the media. Sucrose was advantageous for blastospore production and thermotolerance. The blastospore production reached 3.43×107 spores/mL in liquid culture for 3 days at sucrose concentration of 40 g/L and the LT50 was 1.65 h under 45 °C heat stress. The trehalose in the spores was extracted and quantitatively analyzed by ion chromatography. It was found that the trehalose content in the spores with high heat resistance was generally low, indicating that trehalose is an endogenous substance related to the thermotolerance of blastospores. In summary, choosing an appropriate medium is an effective way to regulate the heat resistance of blastospores and useful for production of high heat-resistant biocontrol preparations of Cordyceps fumosorosea.
生防真菌 / 玫烟色虫草 / 液体发酵 / 芽生孢子 / 耐热性 / 海藻糖 {{custom_keyword}} /
biocontrol fungi / Cordyceps fumosorosea / liquid fermentation / blastospores / thermotolerance / trehalose {{custom_keyword}} /
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Trehalose is a nonreducing disaccharide in which the two glucose units are linked in an alpha,alpha-1,1-glycosidic linkage. This sugar is present in a wide variety of organisms, including bacteria, yeast, fungi, insects, invertebrates, and lower and higher plants, where it may serve as a source of energy and carbon. In yeast and plants, it may also serve as a signaling molecule to direct or control certain metabolic pathways or even to affect growth. In addition, it has been shown that trehalose can protect proteins and cellular membranes from inactivation or denaturation caused by a variety of stress conditions, including desiccation, dehydration, heat, cold, and oxidation. Finally, in mycobacteria and corynebacteria, trehalose is an integral component of various glycolipids that are important cell wall structures. There are now at least three different pathways described for the biosynthesis of trehalose. The best known and most widely distributed pathway involves the transfer of glucose from UDP-glucose (or GDP-glucose in some cases) to glucose 6-phosphate to form trehalose-6-phosphate and UDP. This reaction is catalyzed by the trehalose-P synthase (TPS here, or OtsA in Escherichia coli ). Organisms that use this pathway usually also have a trehalose-P phosphatase (TPP here, or OtsB in E. coli) that converts the trehalose-P to free trehalose. A second pathway that has been reported in a few unusual bacteria involves the intramolecular rearrangement of maltose (glucosyl-alpha1,4-glucopyranoside) to convert the 1,4-linkage to the 1,1-bond of trehalose. This reaction is catalyzed by the enzyme called trehalose synthase and gives rise to free trehalose as the initial product. A third pathway involves several different enzymes, the first of which rearranges the glucose at the reducing end of a glycogen chain to convert the alpha1,4-linkage to an alpha,alpha1,1-bond. A second enzyme then releases the trehalose disaccharide from the reducing end of the glycogen molecule. Finally, in mushrooms there is a trehalose phosphorylase that catalyzes the phosphorolysis of trehalose to produce glucose-1-phosphate and glucose. This reaction is reversible in vitro and could theoretically give rise to trehalose from glucose-1-P and glucose. Another important enzyme in trehalose metabolism is trehalase (T), which may be involved in energy metabolism and also have a regulatory role in controlling the levels of trehalose in cells. This enzyme may be important in lowering trehalose concentrations once the stress is alleviated. Recent studies in yeast indicate that the enzymes involved in trehalose synthesis (TPS, TPP) exist together in a complex that is highly regulated at the activity level as well as at the genetic level.
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The disaccharide trehalose is produced in large quantities by diverse organisms during a variety of stresses. Trehalose prevents proteins from denaturing at high temperatures in vitro, but its function in stress tolerance in vivo is controversial. We report that trehalose stabilizes proteins in yeast cells during heat shock. Surprisingly, trehalose also suppresses the aggregation of denatured proteins, maintaining them in a partially-folded state from which they can be activated by molecular chaperones. The continued presence of trehalose, however, interferes with refolding, suggesting why it is rapidly hydrolyzed following heat shock. These findings reconcile conflicting reports on the role of trehalose in stress tolerance, provide a novel tool for accessing protein folding intermediates, and define new parameters for modulating stress tolerance and protein aggregation.
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