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Fine-scale phylogeographic structure of Borrelia lusitaniae revealed by multilocus sequence typing.

Vitorino LR, Margos G, Feil EJ, Collares-Pereira M, Zé-Zé L, Kurtenbach K - PLoS ONE (2008)

Bottom Line: Uncontaminated cultures as well as infected ticks were included in this study.The results using MLST show that the regional B. lusitaniae populations constitute genetically distinct populations.The study underlines the importance of vertebrate hosts in the geographic spread of tick-borne microparasites.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biologia Vegetal, Centro de Genética e Biologia Molecular, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.

ABSTRACT
Borrelia lusitaniae is an Old World species of the Lyme borreliosis (LB) group of tick-borne spirochetes and prevails mainly in countries around the Mediterranean Basin. Lizards of the family Lacertidae have been identified as reservoir hosts of B. lusitaniae. These reptiles are highly structured geographically, indicating limited migration. In order to examine whether host geographic structure shapes the evolution and epidemiology of B. lusitaniae, we analyzed the phylogeographic population structure of this tick-borne bacterium using a recently developed multilocus sequence typing (MLST) scheme based on chromosomal housekeeping genes. A total of 2,099 questing nymphal and adult Ixodes ricinus ticks were collected in two climatically different regions of Portugal, being approximately 130 km apart. All ticks were screened for spirochetes by direct PCR. Attempts to isolate strains yielded 16 cultures of B. lusitaniae in total. Uncontaminated cultures as well as infected ticks were included in this study. The results using MLST show that the regional B. lusitaniae populations constitute genetically distinct populations. In contrast, no clear phylogeographic signals were detected in sequences of the commonly used molecular markers ospA and ospC. The pronounced population structure of B. lusitaniae over a short geographic distance as captured by MLST of the housekeeping genes suggests that the migration rates of B. lusitaniae are rather low, most likely because the distribution of mediterranean lizard populations is highly parapatric. The study underlines the importance of vertebrate hosts in the geographic spread of tick-borne microparasites.

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Bayesian phylogenetic tree of B. lusitaniae strains based on ospA.The tree was rooted with B. burgdorferi strain B31. Posterior probabilities values are indicated to provide branch support. The scale bar represents 1% sequence divergence. B. lusitaniae samples derived from Grândola are highlighted.
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pone-0004002-g003: Bayesian phylogenetic tree of B. lusitaniae strains based on ospA.The tree was rooted with B. burgdorferi strain B31. Posterior probabilities values are indicated to provide branch support. The scale bar represents 1% sequence divergence. B. lusitaniae samples derived from Grândola are highlighted.

Mentions: Signals of phylogeographic structuring were also found for the individual housekeeping genes and the IGS, but the intrapopulation phylogenies were less resolved (Figures S2, S3, S4, S5, S6, S7, S8, Figure 2). In contrast, the phylogenetic trees of ospA and ospC showed no clear signals of geographic structuring of the B. lusitaniae samples (Figures 3 and 4). For ospC, the lack of geographic structuring may be related to balancing selection and/or recombination. Consistent with this, apart from signatures of positive selection, several recombination events were detected in the ospC sequences using the RDP suite of programs. Recipient and donor strains, position in the alignment and P-values for the individual methods are shown in Table 4. Recombination events will influence the tree topology and may lead to the polytomies that are observed in the ospC tree (Figure 4). No recombination events were detected in ospA using RDP. (The sequences of the IGS, ospA and ospC have been deposited in the GenBank database under accession numbers EF179549 to EF179604.)


Fine-scale phylogeographic structure of Borrelia lusitaniae revealed by multilocus sequence typing.

Vitorino LR, Margos G, Feil EJ, Collares-Pereira M, Zé-Zé L, Kurtenbach K - PLoS ONE (2008)

Bayesian phylogenetic tree of B. lusitaniae strains based on ospA.The tree was rooted with B. burgdorferi strain B31. Posterior probabilities values are indicated to provide branch support. The scale bar represents 1% sequence divergence. B. lusitaniae samples derived from Grândola are highlighted.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2602731&req=5

pone-0004002-g003: Bayesian phylogenetic tree of B. lusitaniae strains based on ospA.The tree was rooted with B. burgdorferi strain B31. Posterior probabilities values are indicated to provide branch support. The scale bar represents 1% sequence divergence. B. lusitaniae samples derived from Grândola are highlighted.
Mentions: Signals of phylogeographic structuring were also found for the individual housekeeping genes and the IGS, but the intrapopulation phylogenies were less resolved (Figures S2, S3, S4, S5, S6, S7, S8, Figure 2). In contrast, the phylogenetic trees of ospA and ospC showed no clear signals of geographic structuring of the B. lusitaniae samples (Figures 3 and 4). For ospC, the lack of geographic structuring may be related to balancing selection and/or recombination. Consistent with this, apart from signatures of positive selection, several recombination events were detected in the ospC sequences using the RDP suite of programs. Recipient and donor strains, position in the alignment and P-values for the individual methods are shown in Table 4. Recombination events will influence the tree topology and may lead to the polytomies that are observed in the ospC tree (Figure 4). No recombination events were detected in ospA using RDP. (The sequences of the IGS, ospA and ospC have been deposited in the GenBank database under accession numbers EF179549 to EF179604.)

Bottom Line: Uncontaminated cultures as well as infected ticks were included in this study.The results using MLST show that the regional B. lusitaniae populations constitute genetically distinct populations.The study underlines the importance of vertebrate hosts in the geographic spread of tick-borne microparasites.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Biologia Vegetal, Centro de Genética e Biologia Molecular, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.

ABSTRACT
Borrelia lusitaniae is an Old World species of the Lyme borreliosis (LB) group of tick-borne spirochetes and prevails mainly in countries around the Mediterranean Basin. Lizards of the family Lacertidae have been identified as reservoir hosts of B. lusitaniae. These reptiles are highly structured geographically, indicating limited migration. In order to examine whether host geographic structure shapes the evolution and epidemiology of B. lusitaniae, we analyzed the phylogeographic population structure of this tick-borne bacterium using a recently developed multilocus sequence typing (MLST) scheme based on chromosomal housekeeping genes. A total of 2,099 questing nymphal and adult Ixodes ricinus ticks were collected in two climatically different regions of Portugal, being approximately 130 km apart. All ticks were screened for spirochetes by direct PCR. Attempts to isolate strains yielded 16 cultures of B. lusitaniae in total. Uncontaminated cultures as well as infected ticks were included in this study. The results using MLST show that the regional B. lusitaniae populations constitute genetically distinct populations. In contrast, no clear phylogeographic signals were detected in sequences of the commonly used molecular markers ospA and ospC. The pronounced population structure of B. lusitaniae over a short geographic distance as captured by MLST of the housekeeping genes suggests that the migration rates of B. lusitaniae are rather low, most likely because the distribution of mediterranean lizard populations is highly parapatric. The study underlines the importance of vertebrate hosts in the geographic spread of tick-borne microparasites.

Show MeSH
Related in: MedlinePlus