Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, Freiburg, Germany.
ISME J. 2010 Nov;4(11):1456-69. doi: 10.1038/ismej.2010.67. Epub 2010 May 27.
Chlorophyll d is a photosynthetic pigment that, based on chemical analyses, has only recently been recognized to be widespread in oceanic and lacustrine environments. However, the diversity of organisms harbouring this pigment is not known. Until now, the unicellular cyanobacterium Acaryochloris marina is the only characterized organism that uses chlorophyll d as a major photopigment. In this study we describe a new cyanobacterium possessing a high amount of chlorophyll d, which was isolated from waters around Heron Island, Great Barrier Reef (23° 26' 31.2″ S, 151° 54' 50.4″ E). The 16S ribosomal RNA is 2% divergent from the two previously described isolates of A. marina, which were isolated from waters around the Palau islands (Pacific Ocean) and the Salton Sea lake (California), suggesting that it belongs to a different clade within the genus Acaryochloris. An overview sequence analysis of its genome based on Illumina technology yielded 871 contigs with an accumulated length of 8 371 965 nt. Their analysis revealed typical features associated with Acaryochloris, such as an extended gene family for chlorophyll-binding proteins. However, compared with A. marina MBIC11017, distinct genetic, morphological and physiological differences were observed. Light saturation is reached at lower light intensities, Chl d/a ratios are less variable with light intensity and the phycobiliprotein phycocyanin is lacking, suggesting that cyanobacteria of the genus Acaryochloris occur in distinct ecotypes. These data characterize Acaryochloris as a niche-adapted cyanobacterium and show that more rigorous attempts are worthwhile to isolate, cultivate and analyse chlorophyll d-containing cyanobacteria for understanding the ecophysiology of these organisms.
叶绿素 d 是一种光合作用色素，基于化学分析，最近才被认为在海洋和湖泊环境中广泛存在。然而，拥有这种色素的生物多样性尚不清楚。到目前为止，单细胞蓝细菌 Acaryochloris marina 是唯一被描述的将叶绿素 d 作为主要光色素的特征生物。在这项研究中，我们描述了一种新的蓝细菌，它含有大量的叶绿素 d，是从大堡礁赫伦岛周围的水域中分离出来的（南纬 23°26'31.2"，东经 151°54'50.4"）。16S 核糖体 RNA 与之前从帕劳群岛（太平洋）和索尔顿海湖（加利福尼亚）水域分离出的两个 A. marina 分离株有 2%的差异，这表明它属于 Acaryochloris 属内的不同进化枝。基于 Illumina 技术对其基因组进行的概述序列分析产生了 871 个连续体，累积长度为 8371965nt。它们的分析显示了与 Acaryochloris 相关的典型特征，例如扩展的叶绿素结合蛋白基因家族。然而，与 A. marina MBIC11017 相比，观察到明显的遗传、形态和生理差异。光饱和在较低的光强度下达到，Chl d/a 比值随光强度变化的变化较小，并且缺乏藻胆蛋白藻蓝蛋白，这表明 Acaryochloris 属的蓝细菌存在不同的生态型。这些数据将 Acaryochloris 描述为一种适应特定生境的蓝细菌，并表明更严格的尝试分离、培养和分析含有叶绿素 d 的蓝细菌是值得的，这有助于理解这些生物的生态生理学。
