Meeks J C, Elhai J, Thiel T, Potts M, Larimer F, Lamerdin J, Predki P, Atlas R
Section of Microbiology, University of California, Davis, CA, 95616, USA,
Photosynth Res. 2001;70(1):85-106. doi: 10.1023/A:1013840025518.
Nostoc punctiforme is a filamentous cyanobacterium with extensive phenotypic characteristics and a relatively large genome, approaching 10 Mb. The phenotypic characteristics include a photoautotrophic, diazotrophic mode of growth, but N. punctiforme is also facultatively heterotrophic; its vegetative cells have multiple developmental alternatives, including terminal differentiation into nitrogen-fixing heterocysts and transient differentiation into spore-like akinetes or motile filaments called hormogonia; and N. punctiforme has broad symbiotic competence with fungi and terrestrial plants, including bryophytes, gymnosperms and an angiosperm. The shotgun-sequencing phase of the N. punctiforme strain ATCC 29133 genome has been completed by the Joint Genome Institute. Annotation of an 8.9 Mb database yielded 7432 open reading frames, 45% of which encode proteins with known or probable known function and 29% of which are unique to N. punctiforme. Comparative analysis of the sequence indicates a genome that is highly plastic and in a state of flux, with numerous insertion sequences and multilocus repeats, as well as genes encoding transposases and DNA modification enzymes. The sequence also reveals the presence of genes encoding putative proteins that collectively define almost all characteristics of cyanobacteria as a group. N. punctiforme has an extensive potential to sense and respond to environmental signals as reflected by the presence of more than 400 genes encoding sensor protein kinases, response regulators and other transcriptional factors. The signal transduction systems and any of the large number of unique genes may play essential roles in the cell differentiation and symbiotic interaction properties of N. punctiforme.
点状念珠藻是一种丝状蓝细菌，具有广泛的表型特征和相对较大的基因组，接近10 Mb。其表型特征包括光合自养、固氮生长模式，但点状念珠藻也是兼性异养的；其营养细胞有多种发育选择，包括末端分化为固氮异形胞以及短暂分化为孢子状厚壁孢子或称为藻殖段的游动丝状体；并且点状念珠藻与真菌和陆生植物具有广泛的共生能力，包括苔藓植物、裸子植物和一种被子植物。联合基因组研究所已完成点状念珠藻菌株ATCC 29133基因组的鸟枪法测序阶段。对一个8.9 Mb数据库的注释产生了7432个开放阅读框，其中45%编码具有已知或可能已知功能的蛋白质，29%是点状念珠藻特有的。序列的比较分析表明该基因组具有高度可塑性且处于动态变化中，有大量插入序列和多位点重复序列，以及编码转座酶和DNA修饰酶的基因。该序列还揭示了编码推定蛋白质的基因的存在，这些蛋白质共同定义了蓝细菌作为一个群体的几乎所有特征。点状念珠藻有广泛的感知和响应环境信号的潜力，这体现在存在400多个编码传感器蛋白激酶、响应调节因子和其他转录因子的基因上。信号转导系统以及众多独特基因中的任何一个都可能在点状念珠藻的细胞分化和共生相互作用特性中发挥重要作用。
