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Phylogenetic analysis of Shiga toxin 1 and Shiga toxin 2 genes associated with disease outbreaks.

Lee JE, Reed J, Shields MS, Spiegel KM, Farrell LD, Sheridan PP - BMC Microbiol. (2007)

Bottom Line: The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1.The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time.These data could indicate that Shiga toxins are experiencing purifying selection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Idaho State University, 921 South 8th Ave,, Pocatello, ID 83209-8007, USA. james.e.lee@amedd.army.mil

ABSTRACT

Background: Shiga toxins 1 and 2 (Stx1 and Stx2) are bacteriophage-encoded proteins that have been associated with hemorrhagic colitis, hemolytic uremic syndrome and other severe disease conditions. Stx1 and Stx2 are genetically and immunologically distinct but share the same compound toxin structure, method of entry and enzymatic function.

Results: Phylogenetic analysis was performed using Stx1 and Stx2 amino acid and nucleotide sequences from 41 strains of Escherichia coli, along with known stx sequences available from GenBank. The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1. The phylograms showed generally flat topologies among our strains' stx1 and stx2 genes. In the stx2 gene, 39.5% of the amino acid sites display very low nonsynonymous to synonymous substitution ratios.

Conclusion: The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time. These data could indicate that Shiga toxins are experiencing purifying selection.

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Related in: MedlinePlus

stx2 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.1 nucleotide substitutions per site.
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Figure 6: stx2 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.1 nucleotide substitutions per site.

Mentions: The nucleotide phylogenetic tree (Figure 6) and the amino acid phylogenetic tree (Figure 7) showed almost the same topology with short branch lengths for our strains. The obvious dissimilarity of Stx2e, Stx2f and Stx2g is striking in both the alignment and phylogenetic trees and is well supported by the high bootstrap values. Idaho strain I7606 had the most divergent sequence among the strains obtained from the Idaho State Health Department and is most closely related to Stx2d A subunit [38]. The lower bootstrap values in the figures are characteristic of highly similar sequences in the branches. Interestingly, the C. freundii Stx2 grouped with the Stx2d group of elastase activated Shiga toxins [39].


Phylogenetic analysis of Shiga toxin 1 and Shiga toxin 2 genes associated with disease outbreaks.

Lee JE, Reed J, Shields MS, Spiegel KM, Farrell LD, Sheridan PP - BMC Microbiol. (2007)

stx2 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.1 nucleotide substitutions per site.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211750&req=5

Figure 6: stx2 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.1 nucleotide substitutions per site.
Mentions: The nucleotide phylogenetic tree (Figure 6) and the amino acid phylogenetic tree (Figure 7) showed almost the same topology with short branch lengths for our strains. The obvious dissimilarity of Stx2e, Stx2f and Stx2g is striking in both the alignment and phylogenetic trees and is well supported by the high bootstrap values. Idaho strain I7606 had the most divergent sequence among the strains obtained from the Idaho State Health Department and is most closely related to Stx2d A subunit [38]. The lower bootstrap values in the figures are characteristic of highly similar sequences in the branches. Interestingly, the C. freundii Stx2 grouped with the Stx2d group of elastase activated Shiga toxins [39].

Bottom Line: The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1.The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time.These data could indicate that Shiga toxins are experiencing purifying selection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Idaho State University, 921 South 8th Ave,, Pocatello, ID 83209-8007, USA. james.e.lee@amedd.army.mil

ABSTRACT

Background: Shiga toxins 1 and 2 (Stx1 and Stx2) are bacteriophage-encoded proteins that have been associated with hemorrhagic colitis, hemolytic uremic syndrome and other severe disease conditions. Stx1 and Stx2 are genetically and immunologically distinct but share the same compound toxin structure, method of entry and enzymatic function.

Results: Phylogenetic analysis was performed using Stx1 and Stx2 amino acid and nucleotide sequences from 41 strains of Escherichia coli, along with known stx sequences available from GenBank. The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1. The phylograms showed generally flat topologies among our strains' stx1 and stx2 genes. In the stx2 gene, 39.5% of the amino acid sites display very low nonsynonymous to synonymous substitution ratios.

Conclusion: The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time. These data could indicate that Shiga toxins are experiencing purifying selection.

Show MeSH
Related in: MedlinePlus