菌丝形态分化与头孢菌素C合成的关系*

利用显微图像分析法对顶头孢霉菌的菌丝形态进行了定量研究,并统计分析了头孢菌素C发酵过程中的菌丝形态的变化规律,具体对菌丝长度、菌丝宽度和菌丝生长单位进行了定量分析,分析了菌丝形态分化与头孢菌素C合成的关系。研究表明头孢菌素C的合成是在细长菌丝分化成膨大菌丝片段后才启动的,头孢菌素C可能主要是在膨大菌丝分化成节孢子的过程中被合成。     

柿树炭疽菌侵染寄主的细胞学研究

超微结构研究表明,柿树炭疽菌(Colletotrichum gloeosporioides)侵染后在寄主细胞中形成初生菌丝和次生菌丝,寄主细胞膜外沉积了一层厚的电子不透明物质,初生菌丝与具有沉积物的寄主原生质膜之间有一层界面基质(interfacial matrix)。当初生菌丝扩张并侵染相邻细胞时,围绕着初生菌丝层的界面基质消失,具有沉积物的原生质膜被逐步降解。初生菌丝在穿透寄主细胞壁过程中形成一个漏斗状的菌丝锥,然后穿透寄主细胞壁并迅速膨大,然后形成厚壁的初生菌丝。初生菌丝在寄主细胞壁中收缩狭窄处产生一个隔膜,隔膜两边菌丝中细胞质的电子密度明显不同,菌丝锥中有浓密的电子密度。死体营养的次生菌丝在死的细胞中繁殖和扩展,并产生分枝。次生菌丝可直接穿透较薄的寄主细胞壁,无缢缩或任何变形现象,菌丝顶端部分未见隔膜产生;在穿透较厚的细胞壁时,靠近顶端处产生隔膜,顶端细胞膨大,使寄主细胞壁撕裂。接种90h后分生孢子盘在枝条表面形成。柿树炭疽菌其侵染过程有两个阶段,即初生菌丝的活体营养阶段和次生菌丝的死体营养阶段。     

枯草芽孢杆菌对杨树水泡溃疡病菌菌丝生长的抑制作用

测定了枯草芽孢杆菌BS-2菌株对杨树水泡溃疡病菌菌丝生长的影响,发现BS-2菌株能够抑制病菌菌丝的生长,并导致菌丝形态畸变,表现为菌丝伸长生长受抑制、扭曲、原生质浓缩、局部膨大成球形或椭圆形以及菌丝断裂和菌丝细胞变成空泡等。BS-2发酵液对病菌菌丝生长也有明显的抑制作用,培养时间越长,其培养液的抑菌作用越强;在不同培养基中获得的发酵液对病菌的抑制效果不同。     

柿树炭疽菌侵染寄主的细胞学研究*

超微结构研究表明,柿树炭疽菌(Colletotrichum gloeosporioides)侵染后在寄主细胞中形成初生菌丝和次生菌丝,寄主细胞膜外沉积了一层厚的电子不透明物质,初生菌丝与具有沉积物的寄主原生质膜之间有一层界面基质(interfacial matrix)。当初生菌丝扩张并侵染相邻细胞时, 围绕着初生菌丝层的界面基质消失,具有沉积物的原生质膜被逐步降解。初生菌丝在穿透寄主细胞壁过程中形成一个漏斗状的菌丝锥,然后穿透寄主细胞壁并迅速膨大, 然后形成厚壁的初生菌丝。初生菌丝在寄主细胞壁中收缩狭窄处产生一个隔膜,隔膜两边菌丝中细胞质的电子密度明显不同,菌丝锥中有浓密的电子密度。死体营养的次生菌丝在死的细胞中繁殖和扩展,并产生分枝。次生菌丝可直接穿透较薄的寄主细胞壁,无缢缩或任何变形现象,菌丝顶端部分未见隔膜产生;在穿透较厚的细胞壁时,靠近顶端处产生隔膜,顶端细胞膨大,使寄主细胞壁撕裂。接种90h后分生孢子盘在枝条表面形成。柿树炭疽菌其侵染过程有两个阶段,即初生菌丝的活体营养阶段和次生菌丝的死体营养阶段。     

猪苓菌丝形成菌核结构的特点

对猪苓(Grifola umbellata(Pers.)Pilat)菌丝在人工条件下形成菌核及繁殖过程、人工菌核与野生菌核及培养基上未形成菌核的猪苓菌丝的显微结构进行了系统研究.研究证明:人工菌核的结构与野生菌核的结构相似,均具有菌髓和皮层结构.人工菌核中的菌丝与培养基表面未形成菌核的猪苓菌丝存在着显著的差异,人工菌核是由培养基上纯培养的菌丝分化为膨大菌丝再由此形成有高度组织分化的猪苓菌核.     

猪苓菌丝形成菌核结构的特点(英文)

对猪苓(Grifolaumbellata(Pers.)Pilat)菌丝在人工条件下形成菌核及繁殖过程、人工菌核与野生菌核及培养基上未形成菌核的猪苓菌丝的显微结构进行了系统研究。研究证明人工菌核的结构与野生菌核的结构相似,均具有菌髓和皮层结构。人工菌核中的菌丝与培养基表面未形成菌核的猪苓菌丝存在着显著的差异,人工菌核是由培养基上纯培养的菌丝分化为膨大菌丝再由此形成有高度组织分化的猪苓菌核。     

不同营养条件下斑玉蕈菌丝生长及产酶特性

分析测定了不同营养条件下斑玉蕈菌丝形态特征、生长速度及产酶规律。低碳氮盐培养基上菌丝生长速度最快,但其菌丝非常稀疏,边缘不整齐,在整个生长阶段酶活力(包括漆酶、锰过氧化物酶、木素过氧化物酶、木聚糖酶、纤维素酶)较低,营养不足对该菌菌丝生长速度影响不明显,但对菌丝形态和酶活有很大的影响;低氮条件下最先产生木质素过氧化物酶,说明限氮条件可以刺激木质素过氧化物酶的产生;高无机盐条件下最先产生漆酶和锰过氧化物酶,但菌丝生长速度较慢,酶活性比较低,浓度过高会影响菌丝生长。结果表明,不同的营养条件对斑玉蕈的菌丝生长及多种酶活性有很大影响,这为斑玉蕈改变营养条件调节菌丝生长速度、菌丝形态以及基质降解提供了理论依据,同时对斑玉蕈栽培过程中基质的高效利用、缩短生产周期、降低生产成本具有重要的指导意义。     

黑曲霉RAF106菌丝球形成的影响因素及对结晶紫的吸附作用

【背景】黑曲霉（Aspergillus niger）作为一种代表性丝状真菌已被广泛用于酶制剂、有机酸、抗生素等高价值代谢产物的工业生产、食品发酵、环境治理等行业,其代谢能力、发酵性能等与菌体形态密切相关。然而,黑曲霉对染料、重金属等的吸附能力与菌体形态的关系鲜有报道。【目的】探究黑曲霉菌丝球形成的影响因素及其对结晶紫的吸附作用。【方法】以从普洱茶分离的黑曲霉RAF106为研究对象,实时监测马铃薯葡萄糖培养液中黑曲霉菌丝球的形成过程;探究培养液的初始pH （4.0-10.0）、培养温度（25-45°C）、孢子接种量（5×10⁴-5×10⁶个/m L）、摇床转速（140-220 r/min）、碳源（葡萄糖、蔗糖、果糖、乳糖、醋酸钠）和氮源（硝酸钠、胰蛋白胨、酵母提取粉、氯化铵）对菌丝球形成的影响;以结晶紫为对象,研究不同菌体形态及菌丝球大小对黑曲霉吸附废水染料能力的影响。【结果】在黑曲霉RAF106中,孢子聚集、菌丝聚集均可形成菌丝球;菌丝球的大小与培养液初始p H、孢子接种量成反比,与摇床转速无关;当温度低于35°C时,菌丝球大小与温度成正比,...     

柿树炭疽菌侵染不同柿树种、品种和部位的细胞学特征

用柿树炭疽病菌Colletotrichumgloeosporioides的分生孢子制备孢子悬浮液,接种无核柿、野柿、冬柿和浙江柿的新梢、叶柄和叶片,并观察致病性、附着胞形成和侵染特性。柿树炭疽菌可以侵染无核柿枝条和叶柄以及野柿枝条,但不侵染无核柿叶片、野柿叶柄和叶片,也不侵染冬柿和浙江柿枝条、叶柄和叶片。室内接种试验与田间自然发病结果一致。柿树炭疽菌在不同柿树表面均能形成附着胞,附着胞产生在寄主表皮背斜细胞壁间结合处(JACWs)或近结合处的百分率达81%~93%。接种12h后,不同柿树表面都有附着胞形成;36h后,无核柿枝条、叶柄中有侵染菌丝存在;48h后,无核柿枝条、叶柄中观察到膨大初生菌丝和较细次生菌丝,初生菌丝可扩展到相邻细胞中,而野柿枝条中仅观察到侵染菌丝;60h后,野柿枝条中也观察到膨大的初生菌丝和较细的次生菌丝,但初生菌丝仅局限在最初侵染的细胞中,无核柿枝条和叶柄以及野柿枝条中都有分枝的次生菌丝在细胞内、细胞间或相邻的细胞中扩展;直到接种90h后,在冬柿和浙江柿上都未观察到侵染菌丝的形成。结果表明,柿树炭疽菌在不同柿树种和品种上侵染菌丝的形成和扩展方式可能是其寄主专化性(或致病性)差异的重要机制之一。     

免疫酶染色法对羊肚菌菌丝特异性靶位的初步定位与分析

为了解羊肚菌(Morchella esculenta)菌丝抗原物质的识别特征及其在菌丝上的分布,利用免疫酶染色法(Immunoenzyme assay,IEA)对两株抗羊肚菌单克隆抗体(W8C9,C6A8)在羊肚菌菌丝上对应的特异性结合靶点进行定位研究。初步确定了两株单克隆抗体对应的羊肚菌菌丝抗原在菌丝上的位置,并确定了W8C9、C6A8和兔多克隆抗体稀释后适合工作的体积分数分别为5.0%、4.5%、4.0%。     

Differentition of mutants of Cephalosporium acremonium in complex medium: the formation of unicellular arthrospores and their germination.

Differentiation of swollen hyphal fragments to unicellular arthrospores accompanied the synthesis of cephalosporin C by a series of Cephalosporium acremonium mutants during propagation in a complex medium. The complex medium supported significantly higher synthesis than the defined medium used in previous studies of differentiation in C. acremonium. The mutants differed in their ability to form unicellular arthrospores and to synthesize cephalosporin C, but a one-to-one correspondence between the two properties was not observed. An inverse relation was observed between the growth rates of the mutants and their ability to synthesize cephalosporin C: each mutant produced more antibiotic but grew more slowly than its parent strain. Germination of the unicellular arthrospores occurred in complex medium but differed significantly from the germination of conidia in seed medium. The unicellular arthrospores were examined by electron microscopy and compared with swollen hyphal fragments and slender hyphal filaments. The unicellular arthrospores had a thicker cell wall, rougher cell surface, and had one or more small identations in their surface. The internal structure of the unicellular arthrospore resembled those of the swollen hyphal fragment and slender hyphal filament. Filaments had lower concentrations of lipid-containing vacuoles which were prevalent in both the swollen hyphal fragments and the unicellular arthrospores.     

Physiological and morphological changes in autolyzingAspergillus nidulans cultures

Physiological and morphological changes in carbon-limited autolyzing cultures of Aspergillus nidulans were described. The carbon starvation arrested conidiation while the formation of filamentous and "yeast-like" hyphal fragments with profoundly altered metabolism enabled the fungus to survive the nutritional stress. The morphological and physiological stress responses, which maintained the cellular integrity of surviving hyphal fragments at the expense of autolyzing cells, were highly concerted and regulated. Moreover, sublethal concentrations of the protein synthesis inhibitor cycloheximide or the mitochondrial uncoupler 2,4-dinitrophenol completely blocked the autolysis. In accordance with the propositions of the free-radical theory of ageing reactive oxygen species accumulated in the surviving fragments with a concomitant increase in the specific superoxide dismutase activity and a continuous decrease in cell viability. Glutathione was degraded extensively in carbon-starving cells due to the action of gamma-glutamyltranspeptidase, which resulted in a glutathione-glutathione disulfide redox imbalance during autolysis.     

Effects of nutrients and culture conditions on morphology in the seed culture ofCephalosporium acremonium ATCC 20339

The objective of this study was to investigate the effects of nutrients and culture conditions on morphology during the seed culture ofC. acremonium ATCC 20339. Morphological factors such as hyphal length, number of tips, number of arthrospores were observed to investigate the relationship between seed morphology and CPC production. During the time course of seed culture, hyphal length was shortened and the number of arthrospores increased rapidly. On the other hand, the number of tips decreased rapidly, and this was closely related to the hyphal length. Mixed nitrogen sources of 3% soybean meal and 1% cotton seed flour were determined as the proper organic nitrogen sources, in terms of the morphological factors in the seed culture. This fact was proven in batch culture for the production of Cephalosporin C. It was also found that a proper agitation speed enhanced the morphological differentiation ofC. acremonium ATCC 20339, thus improving the production of Cephalosporin C.     

Antibiotic Synthesis and Morphological Differentiation of Cephalosporium acremonium

In submerged cultures, Cephalosporium acremonium exists in four morphological forms: hyphae, arthrospores, conidia, and germlings. The phase of hyphal differentiation into arthrospores coincides with the maximum rate of β-lactam antibiotic synthesis. Furthermore, arthrospores, separated by density-gradient centrifugation, possess 40% greater antibiotic-producing activity than any other morphological cell type. In a series of mutants, each with an increased potential to produce β-lactam antibiotics, differentiation into arthrospores was proportional to the increased titer of these antibiotics. Thus, arthrospores exhibit enhanced synthesis of β-lactam antibiotics and appear to be a determining factor in high-yielding mutants. Since a non-antibiotic-producing mutant readily differentiated into arthrospores, antibiotic synthesis and cellular differentiation are not obligately related.     

Regulation of Cdc42 GTPase activity in the formation of hyphae in Candida albicans

The human fungal pathogen Candida albicans can switch between yeast, pseudohyphal, and hyphal morphologies. To investigate whether the distinctive characteristics of hyphae are due to increased activity of the Cdc42 GTPase, strains lacking negative regulators of Cdc42 were constructed. Unexpectedly, the deletion of the Cdc42 Rho guanine dissociation inhibitor RDI1 resulted in reduced rather than enhanced polarized growth. However, when cells lacking both Cdc42 GTPase-activating proteins, encoded by RGA2 and BEM3, were grown under pseudohyphal-promoting conditions the bud was highly elongated and lacked a constriction at its base, so that its shape resembled a hyphal germ tube. Moreover, a Spitzenk?rper was present at the bud tip, a band of disorganized septin was present at bud base, true septin rings formed within the bud, and nuclei migrated out of the mother cell before the first mitosis. These are all characteristic features of a hyphal germ tube. Intriguingly, we observed hyphal-specific phosphorylation of Rga2, suggesting a possible mechanism for Cdc42 activation during normal hyphal development. In contrast, expression of Cdc42(G12V), which is constitutively GTP bound because it lacks GTPase activity, resulted in swollen cells with prominent and stable septin bars. These results suggest the development of hyphal-specific characteristics is promoted by Cdc42-GTP in a process that also requires the intrinsic GTPase activity of Cdc42.     

Study on the hyphal responses of Aspergillus fumigatus

The hyphal responses of an A. fumigatus isolate to a trizolederivative-fluconazole (FCZ) were studied with a Bio-Cell Tracer system. The numerical data were recorded as the original growth rate (Pre-GR), the time needed for FCZ reaching to its target in hypha (τ_on), the growth rate under the FCZ effect (Exp-GR) and the growth rate after FCZ was removed (Post-GR). Based on above numerical data, the inhibitory rates in the exposure and post exposure periods were calculated as the Exp-I% and Post-I% values. It was found there were variable inhibitory rate values (I%) in individual hyphae corresponding to different FCZ concentrations. It was shown by correlation analysis of the numerical data that the Pre-GR values were negatively correlated with the τ_on values and positively correlated with both the Exp-I% and Post-I% values. Additionally, the τ_on values are negatively correlated with the Exp-I% and Post-I% values. Those results suggested that the hyphal growth rate and the susceptibility of the FCZ target be the important factors to determine the hyphal responses to the FCZ effect. Serial morphological alternations were captured while the hyphal growth curves were changing under the FCZ effects. Of the morphological data, the interesting alternations were visualized when the hyphae were affected by 16 μg/ml FCZ. As shifting of the hyphal growth curves, the hyphae were repeatedly seen as swollen tips and germination from the swollen sites. It is indicated that the hyphal tips are the most sensitive parts of this mycelia fungus to the FCZ affects. Additionally, because the hyphal regrowth was observed as germination from the swollen tips before FCZ was removed, an adaptation phenomenon could be proposed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Morphological mutants of Gibberella fujikuroi for enhanced production of gibberellic acid

AIMS: To examine the production of gibberellic acid by selected morphological mutants of Gibberella fujikuroi in liquid cultures. METHODS AND RESULTS: Mutants of G. fujikuroi having different morphological characteristics were selected after UV irradiation. The production of gibberellic acid by mutants that had different hyphal lengths was examined in shake flasks in media with different concentrations of nutrients as well as different volumes of the medium. Fed-batch fermenter study was performed to evaluate the mutant Mor-25 for growth and production of gibberellic acid. The broth was analysed by high performance liquid chromatography for fusaric acid, the common mycotoxin produced by strains of Fusarium. A variety of morphological mutants having different mycelial and soluble pigmentation as well as colony morphologies were generated from G. fujikuroi upon exposure to UV radiation. A nonpigmented mutant (Car-1) was selected as intermediate parent and later, mutants Mor-1 and Mor-25 were selected based on their distinct morphology. The colonies on regeneration agar plates were small, compact and dry. In liquid medium, mutant Mor-25 grew in a micro-pelleted form and the mycelium had short, highly branched hyphae, curly at tips with thick, swollen cells. Mutant Mor-25 grew rapidly in a low-cost medium containing defatted groundnut flour, sucrose and salts. In media with higher nutrient concentrations as well as larger volumes, it produced twofold more gibberellic acid than the parent. Fusaric acid, the common mycotoxin, was absent in the fermentation broth of mutant Mor-25. The mutants have been deposited in National Collection of Industrial Microorganisms (NCIM), National Chemical Laboratory, Pune, India under following culture collection numbers (Car-1, NCIM 1323; Mor-1, NCIM 1322; and Mor-25, NCIM 1321). CONCLUSIONS: Growth of unpigmented, morphological mutants of G. fujikuroi that led to lower viscosity in fermentation broth resulted in increased production of gibberellic acid. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of morphological mutants that have lower viscosity in liquid cultures for gibberellic acid production is not reported earlier. Similar mutants can be useful for other types of fungal fermentations also.     

Morphology and clavulanic acid production of Streptomyces clavuligerus: Effect of stirrer speed in batch fermentations

Streptomyces clavuligerus ATCC 20764 was grown from spore-inocuia on a glycerol, malt extract, bacteriological peptone medium in 5-L batch fermentations at 490, 990, and 1300 rpm. Dry cell weights, clavulanic acid production, and the morphological parameters main hyphal length, total hyphal length, number of tips, and hyphal growth unit were measured. Growth and productivity were hardly dependent on stirrer speed. After early growth fragmentation of long, highly branched mycelia to shorter, less branched fragments occurred. This was followed by regrowth and, at 1300 rpm, a second fragmentation phase. The effect of increasing stirrer speed was to accelerate the initial fragmentation phase. It was clearly possible to obtain the same biomass concentration and clavulanic acid liter, with different morphologies depending on stirrer speed. This shows that for this fermentation at least there is no direct link between morphology and productivity and, hence, that it might be possible to manipulate them independently to improve fermentor performance.     

A year-round study on functional relationships of airborne fungi with meteorological factors

Air sampling was conducted in Waterloo, Canada throughout 1992. Functional relationships between aeromycota and meteorological factors were analysed. The meteorological factors were, in descending order of importance: mean temperature, minimum temperature, maximum temperature, mean wind speed, relative humidity (RH), rain, maximum wind speed and snow. The most important airborne fungal propagules in descending order were: total fungal spores, unidentified Ascomycetes,Cladosporium, Coprinus, unidentified Basidiomycetes,Alternaria and unidentified fungi. Most airborne fungal taxa had highly significant relationship with temperature, butAspergillus/Penicillium, hyphal fragments andEpicoccum did not.Epicoccum and hyphal fragments were positively associated with wind speed. In comparison with other airborne fungal taxa,Leptosphaeria and unidentified Ascomycetes were more closely correlated with rain and RH during the growing season.     

Ribonucleic Acid Synthesis During the Differentiation of Sporangia in the Water Mold Achlya

The role of ribonucleic acid (RNA) synthesis in the development of sporangia in the saprolegniaceous mold Achlya was studied. Methods were developed for growing and treating large populations of mycelia so that the hyphal tips would differentiate into sporangia with considerable synchrony. Under the starvation conditions imposed for the differentiation of sporangia, net RNA, deoxyribonucleic acid (DNA), and protein synthesis ceased. However, incorporation of radioactive precursors into RNA continued at a high rate throughout the period of differentiation, showing that the enzymatic mechanism for RNA synthesis was still in an active state. Actinomycin D inhibited the differentiation of sporangia and the incorporation of labeled precursors into RNA. The level of actinomycin used did not inhibit the normal outgrowth and branching of the mycelia that occurred during differentiation. Thus, DNA-dependent RNA synthesis was required for the differentiation of sporangia. Sucrose gradient analysis of newly synthesized RNA showed that only the ribosomal and soluble fractions of RNA were labeled during vegetative growth. During the differentiation of sporangia, ribosomal and soluble RNA fractions were also labeled, and, in addition, a heterodisperse fraction of labeled RNA which was heavier than ribosomal RNA appeared; this fraction was not evident in the newly synthesized RNA from vegetative mycelia.