Comparative genomics of the restriction-modification systems in Helicobacter pylori
Comparative genomics of the restriction-modification systems in Helicobacter pylori
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DOI：
10.1073/pnas.051612298
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发表时间：
2001-02-27
影响因子：
11.1
通讯作者：
Kong, HM
中科院分区：
文献类型：
--
作者：
Lin, LF;Posfai, J;Kong, HM
幽门螺杆菌是一种革兰氏阴性细菌病原体，其基因组较小，为 1.64-1.67 Mb。根据序列相似性，在两种完全测序的幽门螺杆菌菌株 26695 和 J99 中鉴定出了 20 多个假定的 DNA 限制性修饰 (R-M) 系统，占总基因组的 4% 以上。在这项研究中，我们研究了幽门螺杆菌26695中14个II型R-M系统的生化活性。26695中只有不到30%的II型R-M系统具有完全功能，与菌株J99获得的结果相似。尽管近 90% 的 R-M 基因是两个幽门螺杆菌菌株共有的，但这些 R-M 基因的不同组在每个菌株中都具有功能活性。有趣的是，所有菌株特异性 R-M 基因都是活跃的，而大多数共享基因是不活跃的。这与菌株特异性基因是最近通过从其他细菌的水平转移和选择的远功能获得的概念相一致。因此，它们不太可能受到随机突变的损害。我们的结果还表明，幽门螺杆菌在不同菌株中具有极其多样化的R-M系统，并且可以通过不断获得新的R-M系统以及通过灭活和删除旧的R-M系统来维持多样性。
Helicpbacter pylori is a Gram-negative bacterial pathogen with a small genome of 1.64-1.67 Mb. More than 20 putative DNA restriction-modification (R-M) systems, comprising more than 4% of the total genome, have been identified in the two completely sequenced H. pylori strains, 26695 and J99, based on sequence similarities. In this study, we have investigated the biochemical activities of 14 Type II R-M systems in H. pylori 26695. Less than 30% of the Type II R-M systems in 26695 are fully functional, similar to the results obtained from strain J99. Although nearly 90% of the R-M genes are shared by the two H. pylori strains, different sets of these R-M genes are functionally active in each strain. Interestingly, all strain-specific R-M genes are active, whereas most shared genes are inactive. This agrees with the notion that strain-specific genes have been acquired more recently through horizontal transfer from other bacteria and selected far function. Thus, they are less likely to he impaired by random mutations. Our results also show that H. pylori has extremely diversified R-M systems in different strains, and that the diversity may be maintained by constantly acquiring new R-M systems and by inactivating and deleting the old ones.