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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

stx1 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% are displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.001 nucleotide substitutions per site.
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Figure 2: stx1 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% are displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.001 nucleotide substitutions per site.

Mentions: The phylogenetic trees made from the nucleotide sequences (Figure 2) and the amino acid sequences (Figure 3) were topologically the same with very short branch lengths. Bootstrap replicates in both trees supported the H19/BCL17/I6650 clade and the Shigella dysenteriae/88–1509 clade. The short branch lengths and relatively low bootstrap values can be directly attributed to the low number of informative characters in the analysis.


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)

stx1 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% are displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.001 nucleotide substitutions per site.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: stx1 Maximum Likelihood Nucleotide Phylogenetic Tree (unrooted). Bootstrap values over 50% are displayed. Pipe-delimited strain names indicate identical sequences. Dates and locations of the isolates are shown if available. The horizontal bar shows 0.001 nucleotide substitutions per site.
Mentions: The phylogenetic trees made from the nucleotide sequences (Figure 2) and the amino acid sequences (Figure 3) were topologically the same with very short branch lengths. Bootstrap replicates in both trees supported the H19/BCL17/I6650 clade and the Shigella dysenteriae/88–1509 clade. The short branch lengths and relatively low bootstrap values can be directly attributed to the low number of informative characters in the analysis.

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