Israel D A, Salama N, Krishna U, Rieger U M, Atherton J C, Falkow S, Peek R M
Division of Gastroenterology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
Proc Natl Acad Sci U S A. 2001 Dec 4;98(25):14625-30. doi: 10.1073/pnas.251551698. Epub 2001 Nov 27.
Isolates of the gastric pathogen Helicobacter pylori harvested from different individuals are highly polymorphic. Strain variation also has been observed within a single host. To more fully ascertain the extent of H. pylori genetic diversity within the ecological niche of its natural host, we harvested additional isolates of the sequenced H. pylori strain J99 from its human source patient after a 6-year interval. Randomly amplified polymorphic DNA PCR and DNA sequencing of four unlinked loci indicated that these isolates were closely related to the original strain. In contrast, microarray analysis revealed differences in genetic content among all of the isolates that were not detected by randomly amplified polymorphic DNA PCR or sequence analysis. Several ORFs from loci scattered throughout the chromosome in the archival strain did not hybridize with DNA from the recent strains, including multiple ORFs within the J99 plasticity zone. In addition, DNA from the recent isolates hybridized with probes for ORFs specific for the other fully sequenced H. pylori strain 26695, including a putative traG homolog. Among the additional J99 isolates, patterns of genetic diversity were distinct both when compared with each other and to the original prototype isolate. These results indicate that within an apparently homogeneous population, as determined by macroscale comparison and nucleotide sequence analysis, remarkable genetic differences exist among single-colony isolates of H. pylori. Direct evidence that H. pylori has the capacity to lose and possibly acquire exogenous DNA is consistent with a model of continuous microevolution within its cognate host.
从不同个体分离得到的胃病原体幽门螺杆菌具有高度多态性。在单个宿主内也观察到了菌株变异。为了更全面地确定幽门螺杆菌在其自然宿主生态位内的遗传多样性程度，我们在6年间隔后从其人类源患者中采集了已测序的幽门螺杆菌菌株J99的额外分离株。随机扩增多态性DNA聚合酶链反应（PCR）和对四个不连锁基因座的DNA测序表明，这些分离株与原始菌株密切相关。相比之下，微阵列分析揭示了所有分离株之间遗传内容的差异，而这些差异通过随机扩增多态性DNA PCR或序列分析未被检测到。存档菌株中分布在整个染色体上的几个基因座的开放阅读框（ORF）与近期菌株的DNA不杂交，包括J99可塑性区内的多个ORF。此外，近期分离株的DNA与针对另一个完全测序的幽门螺杆菌菌株26695特异性ORF的探针杂交，包括一个假定的traG同源物。在额外的J99分离株中，遗传多样性模式在相互比较以及与原始原型分离株比较时都有所不同。这些结果表明，在通过宏观比较和核苷酸序列分析确定的明显同质群体中，幽门螺杆菌的单菌落分离株之间存在显著的遗传差异。幽门螺杆菌有能力丢失并可能获取外源DNA的直接证据与在其同源宿主内持续微进化的模型一致。
