Recombination and positive selection contributed to the evolution of Listeria monocytogenes lineages III and IV, two distinct and well supported uncommon L. monocytogenes lineages

• Published in: Infection, genetics and evolution Vol. 11; no. 8; pp. 1881 - 1890
• Main Authors: Tsai, Yeu-Harn Lucy, Maron, Steve B., McGann, Patrick, Nightingale, Kendra K., Wiedmann, Martin, Orsi, Renato H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 01.12.2011; Elsevier
• Subjects: actin; animal pathogens; Animals; Biological and medical sciences; Biological Evolution; Epidemiology. Vaccinations; essential genes; Gene Transfer, Horizontal; General aspects; horizontal gene transfer; Humans; Infectious diseases; Internalins; intragenic recombination; Listeria monocytogenes; Listeria monocytogenes - classification; Listeria monocytogenes - genetics; Listeria monocytogenes - pathogenicity; Medical sciences; Molecular evolution; Molecular Sequence Data; monophyly; Multigene Family; operon; Phylogeny; polymerization; Positive selection; promoter regions; Recombination; Recombination, Genetic; Selection, Genetic; virulence; Virulence genes; Listeria monocytogenes; Molecular evolution; Recombination; Internalins; Virulence genes; Positive selection; Infection; Virulence; Molecular epidemiology; Bacteria; Evolution
• ISSN: 1567-1348; 1567-7257
• DOI: 10.1016/j.meegid.2011.08.001

► Listeriamonocytogenes lineages III and IV form two distinct monophyletic groups. ► Virulence genes evolved by positive selection in lineages III and IV. ► Recombination contributed mainly to the evolution of lineage III isolates. 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.