Concomitant osmotic and chaotropicity-induced stresses in Aspergillus wentii: compatible solutes determine the biotic window
Concomitant osmotic and chaotropicity-induced stresses in Aspergillus wentii: compatible solutes determine the biotic window
复制标题
DOI：
10.1007/s00294-015-0496-8
复制
发表时间：
2015-08-01
期刊：
影响因子：
2.5
通讯作者：
Hallsworth, John E.
中科院分区：
文献类型：
--
作者：
Alves, Flavia de Lima;Stevenson, Andrew;Hallsworth, John E.
虽然溶质诱导的渗透胁迫反应已在真菌中得到很好的表征，但对环境中普遍存在的物质的其他活性知之甚少。定义、鉴定和定量离液性（即物质诱导的大分子系统的不稳定化）的最新方法现在使得能够对微生物应激生物学有新的见解（Cray等人，Curr Opin Biotechnol 33：228-259，2015 a，.我们使用Aspergillus wentii，极端耐溶质的真菌嗜旱菌的范例，以及酵母细胞和酶模型（酿酒酵母和葡萄糖-6-磷酸脱氢酶）和琼脂凝胶化试验，以确定生长速率抑制，细胞内相容的溶质，细胞膨压，抑制酶活性，底物水活性，和应激离液性为12种化学不同的溶质。这些压力源被发现是：（一）积极的（和典型的大分子稳定的亲液剂），包括NaCl和山梨糖醇;（ii）弱到中等离液和非渗透的，这些是乙醇、尿素、乙二醇;（iii）高度离液和促渗透活性的，即NH 4 NO3、MgCl 2、盐酸胍和CaCl 2;或（iv）主要由于低水活度而具有抑制性，即甘油。在千分之一的货币符号0.974水活度，曲霉菌培养的积极的应激源积累低M（r）多元醇千分之一日元100毫克g干重（-1）。低M（r）多元醇（即甘油、甘露醇和阿拉伯糖醇）显示出更有效的渗透调节;对于高M（r）多元醇如甘露醇和二糖海藻糖，饱和溶液的水活度值太高而无效;即0.978和0.970（25 A（0）C）。高度离液的、具有药理活性的物质在生理相关浓度（20.0-85.7 kJ/kg）下表现出应激水平的离液性。我们假设相容溶质的亲液性可以中和离液性，并通过体外琼脂凝胶化试验对模型离液剂尿素、NH 4 NO3、苯酚和MgCl 2进行了测试。亲液相容溶质中，最有效的保护剂是氧化三甲胺和甜菜碱;但脯氨酸、二甲亚砜、山梨糖醇和海藻糖也有效，这取决于离液剂。相比之下，甘油（用作阴性对照的离液序列高的相容性溶质）相对无效。相容溶质的亲液活性被讨论为这些物质可以减轻离液应激物在体内的活性的一种机制。总的来说，这些数据表明，一些物质伴随诱导离液性介导的和渗透压应力，并且相容的溶质最终定义真菌生长和代谢的生物窗口。这些发现对生态生理学分类的有效性，如“嗜盐菌”和“多极端菌”，用于太空探索的生命支持系统的潜在污染，以及食品供应链中的真菌控制都有影响。
Whereas osmotic stress response induced by solutes has been well-characterized in fungi, less is known about the other activities of environmentally ubiquitous substances. The latest methodologies to define, identify and quantify chaotropicity, i.e. substance-induced destabilization of macromolecular systems, now enable new insights into microbial stress biology (Cray et al. in Curr Opin Biotechnol 33:228-259, 2015a, . We used Aspergillus wentii, a paradigm for extreme solute-tolerant fungal xerophiles, alongside yeast cell and enzyme models (Saccharomyces cerevisiae and glucose-6-phosphate dehydrogenase) and an agar-gelation assay, to determine growth-rate inhibition, intracellular compatible solutes, cell turgor, inhibition of enzyme activity, substrate water activity, and stressor chaotropicity for 12 chemically diverse solutes. These stressors were found to be: (i) osmotically active (and typically macromolecule-stabilizing kosmotropes), including NaCl and sorbitol; (ii) weakly to moderately chaotropic and non-osmotic, these were ethanol, urea, ethylene glycol; (iii) highly chaotropic and osmotically active, i.e. NH4NO3, MgCl2, guanidine hydrochloride, and CaCl2; or (iv) inhibitory due primarily to low water activity, i.e. glycerol. At a parts per thousand currency sign0.974 water activity, Aspergillus cultured on osmotically active stressors accumulated low-M (r) polyols to a parts per thousand yen100 mg g dry weight(-1). Lower-M (r) polyols (i.e. glycerol, erythritol and arabitol) were shown to be more effective for osmotic adjustment; for higher-M (r) polyols such as mannitol, and the disaccharide trehalose, water-activity values for saturated solutions are too high to be effective; i.e. 0.978 and 0.970 (25 A(0)C). The highly chaotropic, osmotically active substances exhibited a stressful level of chaotropicity at physiologically relevant concentrations (20.0-85.7 kJ kg(-1)). We hypothesized that the kosmotropicity of compatible solutes can neutralize chaotropicity, and tested this via in-vitro agar-gelation assays for the model chaotropes urea, NH4NO3, phenol and MgCl2. Of the kosmotropic compatible solutes, the most-effective protectants were trimethylamine oxide and betaine; but proline, dimethyl sulfoxide, sorbitol, and trehalose were also effective, depending on the chaotrope. Glycerol, by contrast (a chaotropic compatible solute used as a negative control) was relatively ineffective. The kosmotropic activity of compatible solutes is discussed as one mechanism by which these substances can mitigate the activities of chaotropic stressors in vivo. Collectively, these data demonstrate that some substances concomitantly induce chaotropicity-mediated and osmotic stresses, and that compatible solutes ultimately define the biotic window for fungal growth and metabolism. The findings have implications for the validity of ecophysiological classifications such as 'halophile' and 'polyextremophile'; potential contamination of life-support systems used for space exploration; and control of mycotoxigenic fungi in the food-supply chain.