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Evolution within Australian Salmonella strains
Mark Bergland, Karen Klyczek, Arlin Toro and Dinitra White
Introduction
Salmonella is a Gram-negative, cylindrical rod of
approximately 2 – 0.5 microns. Salmonella enterica
serovar Typhimurium multiplies in the gastrointestinal tract
of many animal species where it usually persists with out
causing disease, however in humans its growth may
result in gastroenteritis. Six to 48 hours following ingestion
of contaminated food or water, nausea and vomiting often
occur followed by diarrhea. The disease is usually selflimiting in healthy adults, but may be more serious in
children and the elderly with underlying medical
conditions. Modern methods of animal husbandry, food
preparation and distribution has resulted in the increase of Bin 14
gastroenteritis in humans in recent years.
Conclusion
The Salmonella isolates are within a major clone
and are closely related. The distribution of the
single-nucleotide polymorphisms appears to be
clumped (Figure 1). Two genes were identified
in the region with the highest number of SNPs.
These genes appear to be regulatory and they
Salmonella genome map
may important role in evolution.
References
Web sites
Salmonella image
http ://www.idph.state.il.us
Salmonella enterica serovar Typhimurium grows in the
gut of almost all animals, both domesticated and wild. The
S. enterica serovar Typhimurium strain LT2 was isolated
in the 1940s. The complete circular genome 4,857 kb and
is has been reported in Nature 413: 852-457 (2001).
General and genomic information of Salmonella
http ://www.salmonella.org/
http ://www.ucalgary.ca/~kesander/sequences.html
National Microbial Pathogen Data R esource
http ://www.nmpdr.org/
The strains of Salmonella enterica serovar typhimurium
used in this study are isolates from bovine, chicken, emu,
human, porcine, alpaca, feline, snake and goat samples
Enteropathogen Resource Integration Center
http ://www.ericbrc.org/portal/eric/
SNP distribution
in different regions of Australia.
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Methods
Online database for E. coli , Shigella an d Salmonella
http ://colibase.bham.ac.uk/
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Number of SNPs identified
Using the data from the Hu et al (2006) paper, we analyzed
the SNP distribution across the Salmonella genome in
Excel (Neuhauser 2007). We sorted identified SNPs into
bins of 250,000 nucleotides each, and determined the
average number of SNPs in each bin. Genes that were
located in a region with a higher SNP number were
investigated.
Articles
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clumped rather than random.
Honghua Hu, Ruiting Lan, and Peter R. Reeves. 2006. Adaptation
of Multi locus Sequencing for Studying Variati on With in a
Major Clone: Evolutionary Relationships of Salmonella
enterica Serovar Typhimurium. Genetic s. 172(2): 743–750.
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Fig. 1. Chromosomal distribution of SNPs. Bin 1
corresponds to nucleotides 1-250,000, bin 2 corresponds to
nucleotides 250,0001-500,000, etc. The average number of
SNPs in each bin and the variance were calculated, and the
ratio of variance to mean indicates that the distribution may be
The Institu te for Genomic Research
http ://www.tigr .org/tdb/
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Neuhauser, C. 2007 SNPs and hypothesis testing. BioQUEST
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Bin
Note: According to the simulation, the 95% confidence limit for the ration is 2.15, so this ratio does not quite
exceed that value and therefore the null hypothesis (that the distribution is random) cannot be rejected.
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