A High-Resolution View of Genome-Wide Pneumococcal Transformation
A High-Resolution View of Genome-Wide Pneumococcal Transformation
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DOI：
10.1371/journal.ppat.1002745
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发表时间：
2012-06-01
期刊：
影响因子：
6.7
通讯作者：
Bentley, Stephen D.
中科院分区：
文献类型：
--
作者：
Croucher, Nicholas J.;Harris, Simon R.;Bentley, Stephen D.
转化是微生物进化的一种重要机制，通过这种机制，细菌可以对临床干预措施做出快速适应；例如，促进疫苗逃避和主要呼吸道病原体肺炎链球菌对青霉素的耐药性产生。为了更详细地描述这一过程，对124株通过体外转化产生的肺炎链球菌的基因组进行了测序并检测了重组事件。这些导入所选标记的重组独立于基因组其他地方的未选择事件，其位置不受供体和受体之间的局部序列相似性或错配修复过程的显著影响。然而，这两种类型的重组有时是镶嵌的，多个不连续的片段起源于同一分子的供体DNA。未选择事件的长度呈指数分布，平均值为2.3kb，这意味着重组是随机分解的，每个碱基的固定概率为4.4×10(-4)BP(-1)。这种重组大小的分布，加上在转移序列中观察到的大插入，表明转化有可能减少细菌基因组的大小，不太可能作为摄取辅助基因组座位的有效机制。
Transformation is an important mechanism of microbial evolution through which bacteria have been observed to rapidly adapt in response to clinical interventions; examples include facilitating vaccine evasion and the development of penicillin resistance in the major respiratory pathogen Streptococcus pneumoniae. To characterise the process in detail, the genomes of 124 S. pneumoniae isolates produced through in vitro transformation were sequenced and recombination events detected. Those recombinations importing the selected marker were independent of unselected events elsewhere in the genome, the positions of which were not significantly affected by local sequence similarity between donor and recipient or mismatch repair processes. However, both types of recombinations were sometimes mosaic, with multiple non-contiguous segments originating from the same molecule of donor DNA. The lengths of the unselected events were exponentially distributed with a mean of 2.3 kb, implying that recombinations are stochastically resolved with a fixed per base probability of 4.4x10(-4) bp(-1). This distribution of recombination sizes, coupled with an observed under representation of large insertions within transferred sequence, suggests transformation has the potential to reduce the size of bacterial genomes, and is unlikely to act as an efficient mechanism for the uptake of accessory genomic loci.