Untitled

Abstract

Forty Aspergillus japonicus and A. aculeatus strains, most of them wild-type isolates, were examined using various molecular and phenotypic techniques. The rDNAs proved to be invariable (even strains of the species A. aculeatus exhibited the same restriction profile), while the strains could be classified into seven different mtDNA RFLP groups. Hybridisation data suggest that six of these mtDNA types have certain common restriction sites, while mtDNA type 7, which was exhibited by some A. aculeatus strains, probably has quite different mtDNA organisation and their size was smallest among the strains studied. The RAPD technique and isoenzyme analysis revealed some variabilities within these RFLP groups and strain specific features could also be recognised. Carbon source assimilation spectra were found to be very distinctive for strains of A. japonicus, A. aculeatus and A. niger, providing a useful tool for pre-characterising new wild-type isolates of black Aspergilli. Only a limited correlation was observed between the dendrograms based on genotypic and phenotypic characters.

β-tubulin paralogue <I>tubC</I> is frequently misidentified as the <I>benA</I> gene in <I>Aspergillus</I> section <I>Nigri</I> taxonomy: primer specificity testing and taxonomic consequences

“…Aspergillus aculeatus and ‘ A. japonicus’ are well-supported species based on molecular data (Pařenicová et al 2001, Samson et al 2007), although both species are indistinguishable based on morphology (Hamari et al 1997). In the past, A. violaceofuscus was treated as a colour variant and synonym of A. aculeatus by Raper & Fennell (1965).…”

Molecular insights into development of Trichoderma interfusants for multistress tolerance enhancing antagonism against Sclerotium rolfsii Sacc

“…The fungal protoplast fusion approach (intraspecific, intergeneric, and interspecific hybridization) is an imperative tool in genetic and physiological research through which potential strains with desirable characteristics could be obtained with minimum interruption in their physiology and biocontrol efficiency (Prabavathy, Mathivanan, Sagadevan, Murugesan, & Lalithakumari, ). The fusant with the ability for mycoparasitism and having the ability to tolerate pH, salt, drought, temperature, fungicides is most effective to control a wide range of pathogens (Hamari et al, ; Hatvani et al, ; Peberdy, ).…”

Genetic diversity of microorganisms

“…16S rRNA快得多, 对于较远的亲缘关系不适用; 16S rRNA大小在 1 500 bp左右, 具有良好的时钟性质, 在结构与功能上具有高度的保守性, 素有"细菌化 石"之称 [24] 。目前, 16S rRNA基因序列分析已广泛应 用于微生物多样性的研究 [25,26] 。此外, 利用 16S rRNA基因序列分析发现了不少新的微生物物种, 尤 其是古细菌的发现, 更是奠定了有关古细菌、真细 菌和真核生物"三界"理论的基础 [27] 。在现实研究中, 统发育及系统演化的研究提供大量的信息 [38] 。 对真菌线粒体DNA的多态性分析已被普遍用于 真菌种群学及进化生物学的研究 [39~41] 。例如, Foury 等 [42] 和Lopez等 [43] 就利用线粒体细胞色素氧化酶亚 基I基因COX1 的多态性作为酵母菌株遗传多样性分 析的工具; Hamari等 [44] 对曲霉属Aspergillus的两个 种Aspergillus japonicus和Aspergillus aculeatus 的分 子特征与表型特征之间的关系作了分析, 他们通过 个种(同种异名)的事件时有发生, 例如, Hu等 [46] 根 据分生孢子特殊的形态结构而将一株捕食线虫真菌 定义为新种, 并命名为多次生节丛孢(Arthrobotrys multisecondarius), 而Li等 [47] 因组突变率高 [56] 。就基因重组而言, 几乎所有真菌 都能通过有性生殖产生基因重组, 而细菌则可通过 转化、接合和转导产生重组。病毒则可通过重组和 重排完成遗传交换 [57] ; 通常情况下, 远距离扩散(如 通过气流或昆虫作为载体)的微生物比短距离扩散 (如通过雨水作为载体、土传、种传)的微生物发生基 因交流的可能性高等等。但目前对于微生物群体遗 传结构的大部分研究工作都局限在对群体的遗传多 样性及地理分布进行简单分析, 而很少探讨群体遗 传结构的时空动态及其进化机制 [56] , 这将是今后群 化形成的 [61] 。杂交物种形成则是由于许多真菌并不 是完全的不育, 从而给个体间的杂交带来了机会。 在草类的内寄生真菌属Epichloe中, 通过杂交产生 无性阶段的Neotyphodium属的真菌能寄生草类, 而 Epichloe属的真菌则不能 [62] 。 此外, 染色体重排在真 菌 的 物 种 形 成 中 也 起 重 要 作 用 , 如 在 子 囊 菌 Sordaria macrospora和担子菌Coprinus cinereus中, 种内的同宗配合使得物种体内含有不同的染色体组 型, 为后代自我繁殖提供了机会 [63] 。除了生殖隔离 在物种形成中发挥重要作用外, 也有学者认为生态 因素可能在共同生存的生物体的物种形成过程中起 重要作用。Rundle和Nosil [64] 将生态学物种形成定义 为, 由生态的分化选择引起的种群间基因流隔离的 过程。在生态学物种形成过程中, 群体间生殖隔离 的进化是分化性选择和生物体对特定环境适应的结 果 [64,65]…”