Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
Infect Genet Evol. 2011 Dec;11(8):1881-90. doi: 10.1016/j.meegid.2011.08.001. Epub 2011 Aug 11.
Listeriamonocytogenes lineages III and IV represent two uncommon lineages of the human and animal pathogen L. monocytogenes, characterized by occurrence of unusual phenotypic and genetic characteristics that differentiate them from the common lineages I and II. To gain further insights into the evolution of lineages III and IV, we amplified and sequenced housekeeping genes (i.e., gap, prs, purM, ribC, and sigB), internalin genes (i.e., inlA, inlB, inlC, inlG, inlC2, inlD, inlE, inlF, and inlH) and the virulence gene cluster containing prfA, plcA, hly, mpl, actA, and plcB for lineages III (n = 7) and IV (n = 4) isolates. Phylogenetic analyses of the sequences obtained along with previously reported sequence data for 40 isolates representing lineages I (n = 18), II (n = 21), and III (n = 1), showed that lineages III and IV represent divergent and monophyletic lineages. The virulence gene cluster as well as the inlAB operon were present in all isolates, with inlF absent from all lineages III and IV isolates. While all lineage IV isolates contained only inlC (in addition to inlAB), lineage III isolates showed considerable diversity with regard to internalin gene presence, including presence of (i) only inlC (n = 2), (ii) inlC and inlGC2DE (n = 3), (iii) only inlGC2DE (n = 2), and (iv) inlC and inlC2DE (n = 1). In addition to evidence for horizontal gene transfer events, among lineages III and IV isolates, in prs, actA, plcB, mpl, inlA, inlB, inlG, inlD, and inlE, we also found significant evidence for positive selection in the hly promoter region and, along the lineages III and IV branches, for actA (including in sites recognized for interactions with proteins involved in actin tail polymerization). In conclusion, lineages III and IV represent two distinct monophyletic groups with contributions of intragenic recombination to the evolution of their internalin genes as well as contributions of positive selection to evolution of the virulence genes island.
李斯特菌属 III 和 IV 谱系代表人类和动物病原体李斯特菌属的两个不常见谱系，其特征是存在不同寻常的表型和遗传特征，使其与常见的 I 和 II 谱系区分开来。为了更深入地了解 III 和 IV 谱系的进化，我们扩增和测序了看家基因（即 gap、prs、purM、ribC 和 sigB）、内化素基因（即 inlA、inlB、inlC、inlG、inlC2、inlD、inlE、inlF 和 inlH）以及包含 prfA、plcA、hly、mpl、actA 和 plcB 的毒力基因簇，用于 III 谱系（n = 7）和 IV 谱系（n = 4）分离株。对获得的序列以及之前报道的 40 个代表 I 谱系（n = 18）、II 谱系（n = 21）和 III 谱系（n = 1）的分离株的序列进行的系统发育分析表明，III 和 IV 谱系代表了不同的单系谱系。毒力基因簇以及 inlAB 操纵子存在于所有分离株中，而所有 III 和 IV 谱系分离株均不存在 inlF。虽然所有 IV 谱系分离株仅含有 inlC（除了 inlAB），但 III 谱系分离株在内化素基因存在方面表现出相当大的多样性，包括（i）仅存在 inlC（n = 2）、（ii）存在 inlC 和 inlGC2DE（n = 3）、（iii）仅存在 inlGC2DE（n = 2）和（iv）存在 inlC 和 inlC2DE（n = 1）。除了在 III 和 IV 谱系分离株中存在水平基因转移事件的证据外，我们还在 prs、actA、plcB、mpl、inlA、inlB、inlG、inlD 和 inlE 中发现了 hly 启动子区域和 III 和 IV 谱系分支中 actA 的正选择的显著证据（包括与参与肌动蛋白尾聚合的蛋白相互作用的位点）。总之，III 和 IV 谱系代表两个不同的单系群体，其内化素基因的进化有基因内重组的贡献，毒力基因岛的进化有正选择的贡献。
