Foster Rachel A, Zehr Jonathan P
Institute of Marine Science, University of California, Santa Cruz, CA 95064, USA.
Environ Microbiol. 2006 Nov;8(11):1913-25. doi: 10.1111/j.1462-2920.2006.01068.x.
Richelia intracellularis is a symbiotic heterocystous cyanobacterium that is capable of forming associations with several genera of diatoms. nifH, 16S rRNA and hetR sequences were amplified and cloned from field populations of Richelia associated with Hemiaulus hauckii (N. Atlantic), with Rhizosolenia clevei (N. Pacific), and from a cultivated isolate of Calothrix associated with Chaetoceros from station ALOHA (N. Pacific). Sequence identity was highest (98.2%) among the 16S rRNA sequences, and more divergent for the hetR (83.8%) and nifH (91.1%) sequences. The hetR and nifH DNA and amino acid sequences obtained from the symbionts associated with the three different diatom genera diverged into three separate lineages supported by high bootstrap values. The data indicate that symbionts in the different hosts are distinct species or strains. Furthermore, three previously unidentified heterocystous-like nifH sequence groups recently reported from station ALOHA in the subtropical Pacific, het-1, het-2 and het-3, were linked to Richelia associated with R. clevei, H. hauckii and the Calothrix symbiont of Chaetoceros sp. respectively.
细胞内利氏藻是一种共生的异形胞蓝细菌，能够与几种硅藻属形成共生关系。从与哈氏半盘藻（北大西洋）、克利夫根管藻（北太平洋）相关的野外群体的细胞内利氏藻，以及从与来自ALOHA站（北太平洋）的角毛藻相关的培养的眉藻分离物中扩增并克隆了nifH、16S rRNA和hetR序列。16S rRNA序列之间的序列同一性最高（98.2%），而hetR（83.8%）和nifH（91.1%）序列的差异更大。从与三种不同硅藻属相关的共生体获得的hetR和nifH DNA及氨基酸序列分化为三个独立的谱系，自展值较高支持了这一点。数据表明，不同宿主中的共生体是不同的物种或菌株。此外，最近在亚热带太平洋的ALOHA站报道的三个先前未鉴定的类异形胞nifH序列组，即het-1、het-2和het-3，分别与与克利夫根管藻、哈氏半盘藻以及角毛藻的眉藻共生体相关的细胞内利氏藻相联系。
