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      Genome sequencing, annotation and comparative genomic analysis of Shigella dysenteriae strain SD1D

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          Abstract

          Background

          Shigellosis is an acute form of gastroenteritis caused by the bacteria belonging to the genus Shigella. It is the most common cause of morbidity and mortality in children. Shigella belongs to the family Enterobactericeae, which is a Gram-negative and rod shaped bacterium. In the present study, we report the draft genome of Shigella dysenteriae strain SD1D, which was isolated from the stool sample of a healthy individual.

          Results

          Based on 16S rRNA gene sequence and phylogenetic analysis, the strain SD1D was identified as Shigella dysenteriae. The draft genome of SD1D consisted of 45, 93, 159 bp with a G + C content of 50.7%, 4, 960 predicted CDSs, 75 tRNAs and 2 rRNAs. The final assembly contained 146 contigs of total length 45, 93, 159 bp with N 50 contig length of 77, 053 bp; the largest contig assembled measured 3, 85, 550 bp.

          Conclusions

          We have for the first time performed the whole genome sequencing of Shigella dysenteriae strain SD1D. The comparative genomic analysis revealed several genes responsible for the pathogenesis, virulence, defense, resistance to antibiotics and toxic compounds, multidrug resistance efflux pumps and other genomic features of the bacterium.

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          Most cited references6

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          Introducing EzTaxon-e: a prokaryotic 16S rRNA gene sequence database with phylotypes that represent uncultured species.

          Despite recent advances in commercially optimized identification systems, bacterial identification remains a challenging task in many routine microbiological laboratories, especially in situations where taxonomically novel isolates are involved. The 16S rRNA gene has been used extensively for this task when coupled with a well-curated database, such as EzTaxon, containing sequences of type strains of prokaryotic species with validly published names. Although the EzTaxon database has been widely used for routine identification of prokaryotic isolates, sequences from uncultured prokaryotes have not been considered. Here, the next generation database, named EzTaxon-e, is formally introduced. This new database covers not only species within the formal nomenclatural system but also phylotypes that may represent species in nature. In addition to an identification function based on Basic Local Alignment Search Tool (blast) searches and pairwise global sequence alignments, a new objective method of assessing the degree of completeness in sequencing is proposed. All sequences that are held in the EzTaxon-e database have been subjected to phylogenetic analysis and this has resulted in a complete hierarchical classification system. It is concluded that the EzTaxon-e database provides a useful taxonomic backbone for the identification of cultured and uncultured prokaryotes and offers a valuable means of communication among microbiologists who routinely encounter taxonomically novel isolates. The database and its analytical functions can be found at http://eztaxon-e.ezbiocloud.net/.
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            Ornithinimicrobium kibberense sp. nov., isolated from the Indian Himalayas.

            A buff-yellow-pigmented bacterium, strain K22-20(T), which was isolated from a cold desert of the Indian Himalayas, was subjected to a polyphasic taxonomic study. Phenotypic and chemical properties of strain K22-20(T) were consistent with its classification in the genus Ornithinimicrobium. The major fatty acids of the strain were iso-C(17 : 1)omega9c (cis-15-methyl 7-hexadecenoic acid), iso-C(15 : 0) (13-methyl tetradecanoic acid), iso-C(16 : 0) (14-methyl pentadecanoic acid) and iso-C(17 : 0) (15-methyl hexadecanoic acid). The G+C content of the genomic DNA was 71 mol%. According to 16S rRNA gene sequence analysis, strain K22-20(T) was closely related to Ornithinimicrobium humiphilum HKI 0124(T) (97.7 %). However, genomic relatedness between strain K22-20(T) and O. humiphilum MTCC 6406(T), as revealed by DNA-DNA hybridization, was 64.5 %. Based on the polyphasic data, strain K22-20(T) (=MTCC 6545(T)=DSM 17687(T)=JCM 12763(T)) represents a novel species of the genus Ornithinimicrobium, for which the name Ornithinimicrobium kibberense sp. nov. is proposed.
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              Genomic analysis of the emergence of 20th century epidemic dysentery

              Background Shigella dysenteriae type 1 (Sd1) causes recurrent epidemics of dysentery associated with high mortality in many regions of the world. Sd1 infects humans at very low infectious doses (10 CFU), and treatment is complicated by the rapid emergence of antibiotic resistant Sd1 strains. Sd1 is only detected in the context of human infections, and the circumstances under which epidemics emerge and regress remain unknown. Results Phylogenomic analyses of 56 isolates collected worldwide over the past 60 years indicate that the Sd1 clone responsible for the recent pandemics emerged at the turn of the 20th century, and that the two world wars likely played a pivotal role for its dissemination. Several lineages remain ubiquitous and their phylogeny indicates several recent intercontinental transfers. Our comparative genomics analysis reveals that isolates responsible for separate outbreaks, though closely related to one another, have independently accumulated antibiotic resistance genes, suggesting that there is little or no selection to retain these genes in-between outbreaks. The genomes appear to be subjected to genetic drift that affects a number of functions currently used by diagnostic tools to identify Sd1, which could lead to the potential failure of such tools. Conclusions Taken together, the Sd1 population structure and pattern of evolution suggest a recent emergence and a possible human carrier state that could play an important role in the epidemic pattern of infections of this human-specific pathogen. This analysis highlights the important role of whole-genome sequencing in studying pathogens for which epidemiological or laboratory investigations are particularly challenging. Electronic supplementary material The online version of this article (doi: 10.1186/1471-2164-15-355) contains supplementary material, which is available to authorized users.
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                Author and article information

                Contributors
                Journal
                Gut Pathog
                Gut Pathog
                Gut Pathogens
                BioMed Central
                1757-4749
                2014
                11 July 2014
                : 6
                : 28
                Affiliations
                [1 ]Microbial Type Culture Collection and Gene bank, CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India
                [2 ]Immunology Laboratory, CSIR-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India
                Article
                1757-4749-6-28
                10.1186/1757-4749-6-28
                4099087
                368e2868-df59-49f4-b0b4-75cabac8cada
                Copyright © 2014 Kaur et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 13 May 2014
                : 2 July 2014
                Categories
                Genome Announcement

                Gastroenterology & Hepatology
                shigella dysenteriae,shigellosis,g + c content,eztaxon,rast
                Gastroenterology & Hepatology
                shigella dysenteriae, shigellosis, g + c content, eztaxon, rast

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