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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Multiple self-splicing introns in the 16S rRNA genes of giant sulfur bacteria
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Multiple self-splicing introns in the 16S rRNA genes of giant sulfur bacteria

机译：巨型硫细菌的16S rRNA基因中的多个自剪接内含子

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摘要

The gene encoding the small subunit rRNA serves as a prominent tool for the phylogenetic analysis and classification of Bacteria and Archaea owing to its high degree of conservation and its fundamental function in living organisms. Here we show that the 16S rRNA genes of not-yet-cultivated large sulfur bacteria, among them the largest known bacterium Thiomargarita namibiensis,regularly contain numerous self-splicing introns of variable length.The 16S rRNA genes can thus be enlarged to up to 3.5 kb. Remarkably, introns have never been identified in bacterial 16S rRNA genes before, although they are the most frequently sequenced genes today. This may be caused in part by a bias during the PCR amplification step that discriminates against longer homologs, as we show experimentally. Such length heterogeneity of 16S rRNA genes has so far never been considered when constructing 16S rRNA-based clone libraries, even though an elongation of rRNA genes due to intervening sequences has been reported previously.The detection of elongated 16S rRNA genes has profound implications for common methods in molecular ecology and may causesystematic biases in several techniques. In this study, catalyzed reporter deposition-fluorescence in situ hybridization on both ribosomes and rRNA precursor molecules as well as in vitro splicing experiments were performed and confirmed self-splicing of the introns. Accordingly, the introns do not inhibit the formation of functional ribosomes.
机译：编码小亚基rRNA的基因由于具有高度的保守性和在生物体中的基本功能，因此成为细菌和古细菌的系统发育分析和分类的重要工具。在这里，我们显示尚未培养的大型硫细菌的16S rRNA基因（其中最大的已知细菌是纳米硫杆菌（Thiomargarita namibiensis））通常包含许多可变长度的自剪接内含子，因此16S rRNA基因可以扩增至3.5 kb。值得注意的是，内含子虽然从未在细菌16S rRNA基因中鉴定过，但是它们是当今最常见的测序基因。如我们的实验所示，这可能部分是由PCR扩增步骤中的偏倚引起的，该偏倚区别于较长的同源物。迄今为止，即使在以前已经报道了由于插入序列导致rRNA基因延长的情况下，构建基于16S rRNA的克隆文库时也从未考虑过16S rRNA基因的这种长度异质性。分子生态学中的方法，可能会导致几种技术出现系统偏差。在这项研究中，在核糖体和rRNA前体分子上进行了催化的报告分子沉积-荧光原位杂交，并进行了体外剪接实验，证实了内含子的自剪接。因此，内含子不抑制功能性核糖体的形成。

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