Molecular-phylogenetic, structural and biochemical features of a cold-adapted, marine ichthyosporean near the animal-fungal divergence, described from in vitro cultures
Molecular-phylogenetic, structural and biochemical features of a cold-adapted, marine ichthyosporean near the animal-fungal divergence, described from in vitro cultures
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DOI：
10.1078/0932-4739-00855
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发表时间：
2002-08-01
影响因子：
2.9
通讯作者：
Landfald, B
中科院分区：
文献类型：
--
作者：
Jostensen, JP;Sperstad, S;Landfald, B
从北极海洋片脚类 Gammarus setosus 中分离出一种迄今为止尚未描述的真核微生物，暂时命名为 Sphaeroforma arctica。基于小亚基核糖体 RNA (SSU-rRNA) 基因的部分序列的系统发育推断，将该生物体与最近建立的鱼孢子纲的 Ichthyophonida 亚支的成员分组。通过 SSU-rDNA 分析，其最接近的亲缘关系是 Pseudoperkinsus Taptis，一种产自伊比利亚半岛的类似 Perkinsus 的蛤类病原体。发现 S. arctica 和 P. Taptis 具有 99.3% 的序列相似性。在所采用的体外生长条件下，生物体表现出连续的营养生长，表现为直径为5-7μm的细胞在源自其亲本细胞的球形壁内稳定增殖。在 12 摄氏度下大约 48 小时后，细胞壁破裂，释放出 120-150 个单个细胞，然后重复该循环。没有观察到出芽、菌丝、变形虫、孢子或有鞭毛的生长阶段。 S. arctica 的线粒体嵴是扁平的。体外培养细胞的细胞壁几乎完全由碳水化合物组成，以N-乙酰半乳糖胺为主要单体，占干重的近70%。多不饱和脂肪酸（主要是二十碳五烯酸和二十二碳六烯酸）约占总脂肪酸的 70%，支持对永久低温下生命的进化适应。我们得出的结论是，S. arctica 是一个新物种，属于原生生物鱼孢子纲中的一个新属。
A hitherto undescribed eukaryotic microorganism, provisionally named Sphaeroforma arctica, was isolated from the arctic marine amphipod Gammarus setosus. Phylogenetic inference based on a partial sequence of the small subunit ribosomal RNA (SSU-rRNA) gene, grouped the organism with members of the Ichthyophonida sub-clade of the recently established class Ichthyosporea. Its closest relative by SSU-rDNA analysis was Pseudoperkinsus tapetis, a Perkinsus-like clam pathogen of the Iberian peninsula. S. arctica and P. tapetis were found to share 99.3% sequence similarity. Under the in vitro growth conditions employed, the organism showed a continuous vegetative growth, manifested as steady proliferation of cells 5-7 mum in diameter within a spherical wall derived from its parent cell. After approximately 48 h at 12 degreesC, the wall ruptured with the release of 120-150 individual cells, and the cycle was repeated. No budding, hyphal, amoeboid, sporal or flagellated growth stages were observed. The mitochondrial cristae of S. arctica, were flattened. The cell wall of cells cultured in vitro was composed almost exclusively of carbohydrates, with N-acetyl-galactosamine as the major monomer, constituting close to 70% of the dry weight. Polyunsaturated fatty acids, mostly eicosapentaenoic and docosahexaenoic acid, constituted approximately 70% of total fatty acids, supporting an evolutionary adaptation to a life at permanently low temperatures. We conclude that S. arctica is a new species belonging to a new genus within the Ichthyosporea class of protists.