Swilaiman Sameira S, O'Gorman Céline M, Balajee S Arunmozhi, Dyer Paul S
School of Biology, University of Nottingham, University Park, Nottingham, United Kingdom.
Eukaryot Cell. 2013 Jul;12(7):962-9. doi: 10.1128/EC.00040-13. Epub 2013 May 6.
Aspergillus lentulus was described in 2005 as a new species within the A. fumigatus sensu lato complex. It is an opportunistic human pathogen causing invasive aspergillosis with high mortality rates, and it has been isolated from clinical and environmental sources. The species is morphologically nearly identical to A. fumigatus sensu stricto, and this similarity has resulted in their frequent misidentification. Comparative studies show that A. lentulus has some distinguishing growth features and decreased in vitro susceptibility to several antifungal agents, including amphotericin B and caspofungin. Similar to the once-presumed-asexual A. fumigatus, it has only been known to reproduce mitotically. However, we now show that A. lentulus has a heterothallic sexual breeding system. A PCR-based mating-type diagnostic detected isolates of either the MAT1-1 or MAT1-2 genotype, and examination of 26 worldwide clinical and environmental isolates revealed similar ratios of the two mating types (38% versus 62%, respectively). MAT1-1 and MAT1-2 idiomorph regions were analyzed, revealing the presence of characteristic alpha and high-mobility-group (HMG) domain genes, together with other more unusual features such as a MAT1-2-4 gene. We then demonstrated that A. lentulus possesses a functional sexual cycle with mature cleistothecia, containing heat-resistant ascospores, being produced after 3 weeks of incubation. Recombination was confirmed using molecular markers. However, isolates of A. lentulus failed to cross with highly fertile strains of A. fumigatus, demonstrating reproductive isolation between these sibling species. The discovery of the A. lentulus sexual stage has significant implications for the management of drug resistance and control of invasive aspergillosis associated with this emerging fungal pathogen.
2005年，扁豆曲霉被描述为烟曲霉复合群中的一个新物种。它是一种机会性人类病原体，可引起侵袭性曲霉病，死亡率很高，已从临床和环境来源中分离出来。该物种在形态上与狭义的烟曲霉几乎相同，这种相似性导致它们经常被误认。比较研究表明，扁豆曲霉具有一些独特的生长特征，并且对包括两性霉素B和卡泊芬净在内的几种抗真菌药物的体外敏感性降低。与曾经被认为是无性繁殖的烟曲霉类似，它只进行有丝分裂繁殖。然而，我们现在表明，扁豆曲霉具有异宗配合的有性繁殖系统。基于PCR的交配型诊断检测到MAT1-1或MAT1-2基因型的分离株，对26株来自世界各地的临床和环境分离株的检查显示，两种交配型的比例相似（分别为38%和62%）。对MAT1-1和MAT1-2特异区域进行了分析，发现存在特征性的α和高迁移率族（HMG）结构域基因，以及其他更不寻常的特征，如MAT1-2-4基因。然后我们证明，扁豆曲霉具有功能性的有性周期，在培养3周后会产生含有耐热子囊孢子的成熟闭囊壳。使用分子标记证实了重组。然而，扁豆曲霉的分离株未能与高度可育的烟曲霉菌株杂交，表明这些姊妹物种之间存在生殖隔离。扁豆曲霉有性阶段的发现对耐药性管理以及与这种新出现的真菌病原体相关的侵袭性曲霉病的控制具有重要意义。
