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首页> 外文期刊>Journal of bacteriology >Evolution of Cyanobacteria by Exchange of Genetic Material among Phyletically Related Strains
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Evolution of Cyanobacteria by Exchange of Genetic Material among Phyletically Related Strains

机译：通过与植物相关菌株之间遗传物质交换的蓝藻进化。

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The cyanobacterial radiation consists of several lineages of phyletically (morphologically and genetically) related organisms. Several of these organisms show a striking resemblance to fossil counterparts. To investigate the molecular mechanisms responsible for stabilizing or homogenizing cyanobacterial characters, we compared the evolutionary rates and phylogenetic origins of the small-subunit rRNA-encoding DNA (16S rDNA), the conserved gene rbcL(encoding d-ribulose 1,5-bisphosphate carboxylase-oxygenase large subunit), and the less conserved gene rbcX. This survey includes four categories of phyletically related organisms: 16 strains of Microcystis, 6 strains of Tychonema, 10 strains of Planktothrix, and 12 strains ofNostoc. Both rbcL and rbcX can be regarded as neutrally evolving genes, with 95 to 100% and 50 to 80% synonymous nucleotide substitutions, respectively. There is generally low sequence divergence within the Microcystis,Tychonema, and Planktothrix categories both forrbcLX and 16S rDNA. The Nostoc category, on the other hand, consists of three genetically clustered lineages for these loci. The 16S rDNA and rbcLX phylogenies are not congruent for strains within the clustered groups. Furthermore, analysis of the phyletic structure for rbcLX indicates recombinational events between the informative sites within this locus. Thus, our results are best explained by a model involving both intergenic and intragenic recombinations. This evolutionary model explains the DNA sequence clustering for the modern species as a result of sequence homogenization (concerted evolution) caused by exchange of genetic material for neutrally evolving genes. The morphological clustering, on the other hand, is explained by structural and functional stability of these characters. We also suggest that exchange of genetic material for neutrally evolving genes may explain the apparent stability of cyanobacterial morphological characters, perhaps over billions of years.
机译：蓝细菌辐射由与谱系（形态和遗传）相关的生物的多个谱系组成。这些生物中有几种与化石相似。为了研究负责稳定或均一化蓝细菌特征的分子机制，我们比较了小亚基编码rRNA的DNA（16S rDNA），保守基因 rbcL （编码d-核糖1,5-二磷酸羧化酶加氧酶大亚基）和保守性较低的基因 rbcX 。这项调查包括与植物相关的四类微生物：16种微囊藻，6种气管炎，10种 Planktothrix 和12种 Nostoc 。 rbcL 和 rbcX 均可被视为中性进化基因，分别具有95％至100％和50％至80％的同义核苷酸取代。对于 rbcLX 和16S rDNA，微囊藻，气管炎和 Planktothrix 类别中的序列差异通常较低。另一方面， Nostoc 类别由这些基因座的三个基因簇谱系组成。 16S rDNA和 rbcLX 系统发育与群集组中的菌株不完全一致。此外，对 rbcLX 的系统结构的分析表明，该基因座内信息位点之间存在重组事件。因此，我们的结果最好通过涉及基因间和基因内重组的模型来解释。这种进化模型解释了现代物种的DNA序列聚类，这是由于遗传物质交换中性进化基因而引起的序列均质化（连续进化）。另一方面，通过这些字符的结构和功能稳定性来解释形态聚类。我们还建议，将遗传物质交换为中性进化的基因可能可以解释蓝藻形态特征的表观稳定性，也许超过数十亿年。

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