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arXiv 1801.07585q-bio.GN
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细菌基因组的通用和特异性特征长度

Universal and idiosyncratic characteristic lengths in bacterial genomes

Ivan Junier, Paul Frémont, Olivier Rivoire

摘要:

在凝聚态物理学中,简化的描述是通过在特定的特征长度上粗粒化系统的特征来获得的,该特征长度被定义为典型的长度,超过该长度,一些属性不再相关。从物理学的角度来看,体外DNA因此具有300个碱基对(bp)的特征长度,分子的库恩长度超过其取向的相关性通常会丢失。从生物学的角度来看,体内DNA具有1000 bp的特征长度,这是基因的典型长度。由于细菌生活在非常不同的物理化学条件下,并且由于它们的基因组缺乏翻译不变性,因此是否存在更大的通用特征长度是一个重要的问题。在这里,我们利用公共数据库中大量的完全测序的基因组来研究这个问题。通过分析GC含量的相关性和数百个细菌染色体中基因背景(同线性)的进化保守性,我们得出结论,可以定义约10-20 kb的基本特征长度。这种特征长度反映了参与基因表达协调的基本结构,这些基本结构存在于几乎所有细菌的基因组中。从技术上讲,得出这一结论需要我们实施对大的特异性基因组特征的存在不敏感的方法,这些特征可能与这些基本的通用结构共存。

英文摘要:

In condensed matter physics, simplified descriptions are obtained by coarse-graining the features of a system at a certain characteristic length, defined as the typical length beyond which some properties are no longer correlated. From a physics standpoint, in vitro DNA has thus a characteristic length of 300 base pairs (bp), the Kuhn length of the molecule beyond which correlations in its orientations are typically lost. From a biology standpoint, in vivo DNA has a characteristic length of 1000 bp, the typical length of genes. Since bacteria live in very different physico-chemical conditions and since their genomes lack translational invariance, whether larger, universal characteristic lengths exist is a non-trivial question. Here, we examine this problem by leveraging the large number of fully sequenced genomes available in public databases. By analyzing GC content correlations and the evolutionary conservation of gene contexts (synteny) in hundreds of bacterial chromosomes, we conclude that a fundamental characteristic length around 10-20 kb can be defined. This characteristic length reflects elementary structures involved in the coordination of gene expression, which are present all along the genome of nearly all bacteria. Technically, reaching this conclusion required us to implement methods that are insensitive to the presence of large idiosyncratic genomic features, which may co-exist along these fundamental universal structures.

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