Functional Relatedness of Shigella Genomes

Fifth International Symposium on Recent Advances in Environmental Health Research POSTER SESSION A

PA - 49

FUNCTIONAL RELATEDNESS OF SHIGELLA GENOMES

Donee’ McAllister, Wellington K. Ayensu, Hari H.P. Cohly and Raphael D. Isokpehi

Center for Bioinformatics & Computational Biology, Department of Biology, Jackson State University, Jackson MS 39217, USA

Abstract: Shigella belongs to Gram-negative, non-spore forming, faculative anaerobic bacilli group of bacteria species. These groups of bacteria have common biochemical and antigenic relationship with Escherichia coli. Shigella is found within the genus of gamma proteobacteria within the family Enterobacteriaceae. The fundamental characteristic in disease pathogenesis associated with Shigella is its invasiveness and the capability to colonize human intestinal epithelium. Diseases associated with Shigella species are acquired usually through drinking water contaminated with human feces or food products processed with contaminated water. Resulting diseases from Shigella species are generally referred to as Shigellosis. Symptoms of Shigellosis include diarrhea, fever, abdominal cramps, vomiting, and headaches. Treatment schedules usually involve the use of antibiotics such as ampicillin, trimethoprim, nalidixic acid, and ciprofloxacin, agents that attack growing organisms at the membrane and nuclear levels. There are four species of Shigella. Shigella boydii (with 18 serotypes), S. dysenteriae (13 serotypes) causes deadly epidemics in many developing regions and nations. S. flexneri (15 serotypes) accounts for a third of the cases of Shigellosis in the United States. S. sonnei that has only one serotype accounts for two thirds of all Shigellosis in the United States. Shigella continues to have an important global impact, causing an estimated 1 million deaths and 163 million cases of dysentery annually. The objectives of this study were (i) to generate the genome statistics and status of genomes of Shigella and (ii) to cluster finished genomes of Shigella species based on functional profiles. Six finished genomes and two draft genomes of Shigella were identified. None of the finished genomes had identical genome size. Among the finished genomes, S. flexneri 2a 301 genome had the largest gene count of 4852 while S. flexneri 5 8401 had the smallest gene count of 4390. S. dysenteriae Sd197 has the smallest genome size of 4.56Mb. Shigella sonnei Ss046 had the largest genome size of 5.05 Mb. S. flexneri 5 8401 genome is closer to the genomes of S. boydii and S. sonnei. A correlation coefficient of 0.76 was observed as the minimal relatedness. S. dysenteriae Sd197 formed a distinct cluster from the other Shigella genomes. Shigella dysenteriae type 1 produces severe disease and may be associated with life-threatening complications (PMID: 15880088). The gene complement of S. flexneri 5b is smaller than S. flexneri 2a mainly because the former lacks the SHI-1 pathogenicity island (PAI) (PMID: 16822325); S. flexneri 5b clustered with S. boydii and S. sonnei. The virulence of Shigella species is in the order S. dysenteriae > S. flexneri > S. sonnei (PMID: 16275786). S. boydii is found mainly on the sub-continent of India. S. dysenteriae genome formed a functionally distinct cluster from the other three Shigella genomes. Shigella flexneri 5b genome was more functionally related to S. boydii and S. sonnei than to S. flexneri 2b.

Acknowledgements: U.S. Department of Homeland Security under Grant Award Number 2007-ST- 104-000007 (Bioinformatics in Biodefense Career Development Program); Mississippi NSF-EPSCoR “Innovations through Computational Sciences” Award (EPS-0556308); Research Centers in Minority Institutions (RCMI) – Center for Environmental Health (NIH-NCRR G12RR13459-09). Disclaimer: “The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the funding agencies.