Claverys J P, Prudhomme M, Mortier-Barrière I, Martin B
Laboratoire de Microbiologie et Génétique Moléculaire CNRS-UPR 9007, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France.
Mol Microbiol. 2000 Jan;35(2):251-9. doi: 10.1046/j.1365-2958.2000.01718.x.
Genetic plasticity plays a central role in the biology of the human pathogen Streptococcus pneumoniae. This is illustrated by the existence of at least 90 different capsular types (the polysaccharide capsule has an essential antiphagocytic function) as well as by the rapid emergence of penicillin-resistant (PenR) pneumococcal isolates. Natural genetic transformation is believed to be essential for this genetic plasticity; capsular types can be switched by intraspecies transformation, whereas interspecies transformation is responsible for the appearance, in the PenR isolates, of mosaic pbp genes, which encode proteins with reduced affinity for penicillin. Data on the regulation of competence for transformation in S. pneumoniae, on the control of intra- and interspecies genetic exchange and on the shuffling and capture of exogenous sequences during transformation are reviewed. Possible links between transformation and changes in environmental conditions are discussed, and the adaptive 'strategy' deduced for S. pneumoniae is compared with that of Escherichia coli.
遗传可塑性在人类病原体肺炎链球菌的生物学特性中起着核心作用。这体现在至少90种不同荚膜类型的存在（多糖荚膜具有重要的抗吞噬功能）以及青霉素耐药（PenR）肺炎链球菌分离株的迅速出现。自然遗传转化被认为是这种遗传可塑性所必需的；荚膜类型可通过种内转化进行切换，而种间转化则导致PenR分离株中出现镶嵌型pbp基因，这些基因编码的蛋白质对青霉素的亲和力降低。本文综述了肺炎链球菌转化能力的调控、种内和种间基因交换的控制以及转化过程中外源序列的重排和捕获的数据。讨论了转化与环境条件变化之间可能存在的联系，并将推导得出的肺炎链球菌的适应性“策略”与大肠杆菌的进行了比较。
