Macrorecombination in isolated cell pairs via natural genetic transformation

摘要/摘要： 肺炎链球菌(简称肺炎球菌)是一种主要的全球细菌性人类病原体，可引起 全世界每年约有100万人死于肺炎、败血症和脑膜炎。两种策略 是用来对抗这种感染的。抗生素通常可以治愈这种感染，而疫苗是 用来减少最危险的血清型的循环种群。然而，两者 战略正在以越来越快的速度失败。抗生素耐药菌株不断出现， 在全球传播；疫苗接种效果也受到挑战，因为没有针对性的血清型 根据目前的疫苗配方，疫苗配方不断涌现，并迅速取代目标疫苗。 这些失败的原因是将多个外来基因转移到细菌中，但 产生新的传染性和抗药性毒株类型的机制尚不清楚。传输事件 有两种类型，称为微观重组事件和宏观重组事件。微观事件，涉及 几十到几千个碱基对，与已知的基因属性一致 肺炎球菌中的转化转移。然而，更重要的事件涉及转移 数以万计的核苷酸组成的多个区块，有时都来自一个供体菌株。 这些宏观重组事件很难与任何已知的 基因转移的机制--无论是接合、转导还是转化。这个项目 会使用微流体创造无数的小室(液滴)，攻击者在其中- 靶相互作用可首次在细胞和 分子水平，既通过识别参与细胞，也通过跟踪所有基因交换事件 全基因组规模和200个碱基对的分辨率。 医学上的相关性。大多数致病性链球菌的基因转移机制都是通过 自然遗传转化。遗传转化是遗传灵活性的重要途径 在肺炎球菌中，它被记录为疫苗逃逸、产生和传播的关键 新的耐药基因。因为肺炎链球菌是一种 对DNA摄取的研究，这项工作是关于意外地转移大块DNA的机制 菌株或物种之间的基因将对理解和靶向 革兰氏阳性菌之间许多类似的肽调控基因交换系统 通常与这些细菌致病的能力有关。

Abstract /Summary: Streptococcus pneumoniae (pneumococcus) is a major global bacterial human pathogen, causing ~1 million deaths annually worldwide, due to pneumonia, sepsis, and meningitis. Two strategies are used to combat such infections. Antibiotics can often cure such infections, and vaccines are used to reduce the circulating populations of the most dangerous serotypes. However, both strategies are failing at an increasing rate. Antibiotic resistant strains are continually arising and spreading globally; vaccination effectiveness is also under challenge, as serotypes not targeted by current vaccine formulations are continually arising and rapidly replacing the targeted ones. The cause of these failures is transfer of multiple foreign genes into the bacteria, but the mechanisms that create the new infectious and resistant strain types are unclear. Transfer events are of two types, named as micro- and macro-recombination events. The micro events, involving dozens to several thousands of base pairs, are consistent with the known properties of gene transfer by transformation in pneumococcus. However, more significant events involve transfer of multiple blocks of tens of thousands of nucleotides, sometimes all from a single donor strain. These macro-recombination events were difficult to reconcile completely with any known mechanism of gene transfer - whether conjugation, transduction, or transformation. This project would use microfluidics to create numerous small chambers (droplets) within which attacker- target interactions can be studied and characterized for the first time at both the cellular and molecular levels, both by identifying the participant cells and by tracing all gene exchange events at full genome scale and 200-bp resolution. Medical Relevance. Most pathogenic streptococci share the mechanism of gene transfer by natural genetic transformation. Genetic transformation is an important path for genetic flexibility in pneumococcus, where it is documented as key to vaccine escape and creation and spread of new drug-resistance genes. Because Streptococcus pneumoniae is a model organism for the study of DNA uptake, this work on the mechanism that transfers unexpectedly large blocks of genes between strains or species will have broad impacts on understanding and targeting the many similar peptide regulated gene exchange systems among Gram positive bacteria that are often associated with the ability of these bacteria to cause disease.