Phylogeographic Analysis of Tick-borne Pathogen - Recent Advances and Issues in Environmental Science - page 85

Table 3. Top table shows the genetic distances among and between the MSP1a R1 repeat sequences
reported on each ecoregion cluster.
Ecoregion

Cluster 1 Cluster 2 Cluster 3 Cluster 4

Cluster 1 0.212 0.311 0.319 0.337

Cluster 2 0.199 0.321 0.371

Cluster 3 0.175 0.214

Cluster 4 0.156

Geographical cluster Western USA Eastern USA Mesoamerican+ Caribbean South America

Western USA 0.418 0.399 0.514 0.519

Eastern USA 0.329 0.388 0.501

Mesoamerican+ 0.454 0.455

Caribbean
South America 0.521

Discriminant analysis showed that 74.8% of MSP1a RL sequences were found
associated with one ecoregion cluster only (Figure 3, Table 2). Seven RL sequences
(25% of the total number of RL sequences) were reported exclusively in ecoregion
cluster 1, with 61.2% identical amino acids. Five RL sequences (17.8%) were reported
solely in ecoregion cluster 2 with 64.5% identical amino acids. Twelve RL sequences
(32%) were found only in ecoregion cluster 3, sharing 61.2% of their amino acids.
No RL unique sequences were found in ecoregion cluster 4. The differences in RL
consensus sequences between ecoregion clusters 1 and 2, 2 and 3, and 1 and 3 were
16%, 26%, and 32%, respectively. In contrast to A. marginale MSP1a R1 repeat se-
quences, the RL sequences within each ecoregion cluster did not appear to be under
positive selection as shown by d N /d S indexes of 0.89, 0.79, and 0.77 for ecoregion
clusters 1 to 3, respectively. Mantel's test on RL sequences was 0.87 (P < 0.001) when
applied to ecoregion clusters using only unique sequences. This value dropped to 0.82
(P < 0.001) when every strain in the ecoregion clusters was included in the analysis.
The same test provided a value of 0.27 (P = 0.208) for the distances matrix based on
geographical association of strains. When the MSP1a Rn repeats, located between R1
and RL were analyzed, a total of 30, 9, 17, and 3 sequences were ascribed to ecore-
gion clusters 1-4, respectively. The Rn consensus sequences contained 14 (45.2%),
17 (54.9%), 17 (54.9%), and 24 (77.4%) identical amino acids in ecoregions clusters
1 to 4, respectively. The number of R1, Rn and RL repeat sequences varied between
ecoregion clusters without a clear pattern.

Anaplasma marginale MSP1a Microsatellite Sequences Have Ecoregion-
specific Signatures and Affect Gene Expression in Escherichia coli
The analysis of the MSP1a microsatellite sequences resulted in nine different geno-
types among A. marginale strains (Table 1). The different microsatellite sequences
produced SD-ATG distances of between 19 and 29 nucleotides, but the predominant
distance was 23 nucleotides in all regions (Table 1).
The analysis of MSP1a microsatellite sequences showed phylogeographic clus-
tering of some genotypes (Table 1). However, only three of the eight microsatellite