Yamamoto Haruki, Uesaka Kazuma, Tsuzuki Yuki, Yamakawa Hisanori, Itoh Shigeru, Fujita Yuichi
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
Center for Gene Research, Nagoya University, Nagoya 464-8601, Japan.
Microorganisms. 2022 Jul 7;10(7):1374. doi: 10.3390/microorganisms10071374.
Acaryochloris is a marine cyanobacterium that synthesizes chlorophyll d, a unique chlorophyll that absorbs far-red lights. Acaryochloris is also characterized by the loss of phycobiliprotein (PBP), a photosynthetic antenna specific to cyanobacteria; however, only the type-strain A. marina MBIC11017 retains PBP, suggesting that PBP-related genes were reacquired through horizontal gene transfer (HGT). Acaryochloris is thought to have adapted to various environments through its huge genome size and the genes acquired through HGT; however, genomic information on Acaryochloris is limited. In this study, we report the complete genome sequence of A. marina MBIC10699, which was isolated from the same area of ocean as A. marina MBIC11017 as a PBP-less strain. The genome of A.marina MBIC10699 consists of a 6.4 Mb chromosome and four large plasmids totaling about 7.6 Mb, and the phylogenic analysis shows that A.marina MBIC10699 is the most closely related to A. marina MBIC11017 among the Acaryochloris species reported so far. Compared with A. marina MBIC11017, the chromosomal genes are highly conserved between them, while the genes encoded in the plasmids are significantly diverse. Comparing these genomes provides clues as to how the genes for PBPs were reacquired and what changes occurred in the genes for photosystems during evolution.
蓝藻绿球藻是一种海洋蓝细菌，它能合成叶绿素d，这是一种独特的能吸收远红光的叶绿素。蓝藻绿球藻的另一个特征是缺乏藻胆蛋白（PBP），藻胆蛋白是蓝细菌特有的光合天线；然而，只有模式菌株滨海蓝藻绿球藻MBIC11017保留了藻胆蛋白，这表明与藻胆蛋白相关的基因是通过水平基因转移（HGT）重新获得的。蓝藻绿球藻被认为通过其巨大的基因组大小和通过水平基因转移获得的基因适应了各种环境；然而，关于蓝藻绿球藻的基因组信息有限。在本研究中，我们报告了滨海蓝藻绿球藻MBIC10699的完整基因组序列，它是从与滨海蓝藻绿球藻MBIC11017相同的海洋区域分离出来的，是一种无藻胆蛋白的菌株。滨海蓝藻绿球藻MBIC10699的基因组由一条6.4 Mb的染色体和四个大质粒组成，总计约7.6 Mb，系统发育分析表明，在迄今为止报道的蓝藻绿球藻物种中，滨海蓝藻绿球藻MBIC10699与滨海蓝藻绿球藻MBIC11017的亲缘关系最为密切。与滨海蓝藻绿球藻MBIC11017相比，它们的染色体基因高度保守，而质粒中编码的基因则有显著差异。比较这些基因组为藻胆蛋白基因如何重新获得以及光合作用系统基因在进化过程中发生了哪些变化提供了线索。
