Vilela Raquel, Mendoza Leonel
Biomedical Laboratory Diagnostics, Michigan State University, East Lansing, MI 48424-1031, USA.
Rev Iberoam Micol. 2012 Oct-Dec;29(4):185-99. doi: 10.1016/j.riam.2012.03.012. Epub 2012 Apr 12.
Rhinosporidum seeberi is the etiologic agent of rhinosporidiosis, a disease of mucous membranes and infrequent of the skin and other tissues of humans and animals. Because it resists culture, for more than 100 years true taxonomic identity of R. seeberi has been controversial. Three hypotheses in a long list of related views have been recently introduced: 1) a prokaryote cyanobacterium in the genus Microcystis is the etiologic agent of rhinosporidiosis, 2) R. seeberi is a eukaryote pathogen in the Mesomycetozoa and 3) R. seeberi is a fungus. The reviewed literature on the electron microscopic, the histopathological and more recently the data from several molecular studies strongly support the view that R. seeberi is a eukaryote pathogen, but not a fungus. The suggested morphological resemblance of R. seeberi with the genera Microcystis (bacteria), Synchytrium and Colletotrichum (fungi) by different teams is merely hypothetical and lacked the scientific rigor needed to validate the proposed systems. A fundamental aspect against the prokaryote theory is the presence of nuclei reported by numerous authors and updated in this review. Moreover, Microcystis's and Synchytrium's ultra-structural and key cell cycle traits cannot be found in R. seeberi parasitic phase. The PCR amplification of a cyanobacteria 16S rDNA sequence from cases of rhinosporidiosis, while intriguing, will be viewed here as an anomaly due to contamination with environmental Microcystis or perhaps as an endosymbiotic acquisition of plastids from cyanobacteria ancestors. Thus, even if R. seeberi possesses prokaryote DNA, this does not prove that R. seeberi is a cyanobacterium. The placement of R. seeberi within the fungi is scientifically untenable. The isolation and the DNA analysis performed in a fungal strain, and the lack of appropriate controls are the main problems of this claim. Further studies are needed to validate R. seeberi's acquisition of prokaryote plastids and other issues that still need careful scrutiny.
西伯鼻孢子菌是鼻孢子虫病的病原体，这是一种发生于黏膜的疾病，在人类和动物的皮肤及其他组织中较为少见。由于它难以培养，100多年来，西伯鼻孢子菌的真正分类地位一直存在争议。最近在众多相关观点中提出了三种假说：1）微囊藻属的一种原核蓝细菌是鼻孢子虫病的病原体；2）西伯鼻孢子菌是中生动物亚界的一种真核病原体；3）西伯鼻孢子菌是一种真菌。回顾有关电子显微镜、组织病理学以及最近来自多项分子研究的数据的文献，有力地支持了西伯鼻孢子菌是一种真核病原体而非真菌的观点。不同研究团队提出的西伯鼻孢子菌与微囊藻属（细菌）、集壶菌属和炭疽菌属（真菌）在形态上的相似性仅仅是假设，缺乏验证所提出系统所需的科学严谨性。反对原核生物理论的一个基本方面是众多作者报告并在本综述中更新的细胞核的存在。此外，在西伯鼻孢子菌的寄生阶段找不到微囊藻属和集壶菌属的超微结构及关键细胞周期特征。从鼻孢子虫病病例中PCR扩增蓝细菌16S rDNA序列虽然很有趣，但在此将其视为由于环境微囊藻污染或可能是从蓝细菌祖先内共生获得质体而导致的异常情况。因此，即使西伯鼻孢子菌拥有原核生物DNA，这也不能证明西伯鼻孢子菌是一种蓝细菌。将西伯鼻孢子菌归为真菌在科学上是站不住脚的。在一种真菌菌株中进行的分离和DNA分析以及缺乏适当对照是这一观点的主要问题。需要进一步研究来验证西伯鼻孢子菌获得原核生物质体以及其他仍需仔细审查的问题。
