Comparative Genome Analysis of Helicobacter pylori Strains

DNA macroarrays were used to characterize 17 Helicobacter pylori strains isolated in four geographic regions of Russia (Moscow, St. Petersburg, Kazan, and Novosibirsk). Of all genes, 1272 (81%) proved to occur in all strains and to constitute a functional core of the genome, and 293 (18.7%) were strain-specific and greatly varied among the H. pylori strains. Most (71%) of the latter had unknown functions; the remainder included restriction–modification genes (3–9%), transposition genes (2–4%), and genes coding for outer membrane proteins (2–4%). The Russian H. pylori strains did not differ in genome organization or in the number and distribution of strain-specific genes from strains isolated in other countries.     

Comparative Genomic Analysis of East Asian and Non-Asian Helicobacter pylori Strains Identifies Rapidly Evolving Genes

Helicobacter pylori infection is a risk factor for the development of gastric adenocarcinoma, a disease that has a high incidence in East Asia. Genes that are highly divergent in East Asian H. pylori strains compared to non-Asian strains are predicted to encode proteins that differ in functional activity and could represent novel determinants of virulence. To identify such proteins, we undertook a comparative analysis of sixteen H. pylori genomes, selected equally from strains classified as East Asian or non-Asian. As expected, the deduced sequences of two known virulence determinants (CagA and VacA) are highly divergent, with 77% and 87% mean amino acid sequence identities between East Asian and non-Asian groups, respectively. In total, we identified 57 protein sequences that are highly divergent between East Asian and non-Asian strains, but relatively conserved within East Asian strains. The most highly represented functional groups are hypothetical proteins, cell envelope proteins and proteins involved in DNA metabolism. Among the divergent genes with known or predicted functions, population genetic analyses indicate that 86% exhibit evidence of positive selection. McDonald-Kreitman tests further indicate that about one third of these highly divergent genes, including cagA and vacA, are under diversifying selection. We conclude that, similar to cagA and vacA, most of the divergent genes identified in this study evolved under positive selection, and represent candidate factors that may account for the disproportionately high incidence of gastric cancer associated with East Asian H. pylori strains. Moreover, these divergent genes represent robust biomarkers that can be used to differentiate East Asian and non-Asian H. pylori strains.     

Comparative Genomics of a Helicobacter pylori Isolate from a Chinese Yunnan Naxi Ethnic Aborigine Suggests High Genetic Divergence and Phage Insertion

Helicobacter pylori is a common pathogen correlated with several severe digestive diseases. It has been reported that isolates associated with different geographic areas, different diseases and different individuals might have variable genomic features. Here, we describe draft genomic sequences of H. pylori strains YN4-84 and YN1-91 isolated from patients with gastritis from the Naxi and Han populations of Yunnan, China, respectively. The draft sequences were compared to 45 other publically available genomes, and a total of 1059 core genes were identified. Genes involved in restriction modification systems, type four secretion system three (TFS3) and type four secretion system four (TFS4), were identified as highly divergent. Both YN4-84 and YN1-91 harbor intact cag pathogenicity island (cagPAI) and have EPIYA-A/B/D type at the carboxyl terminal of cagA. The vacA gene type is s1m2i1. Another major finding was a 32.5-kb prophage integrated in the YN4-84 genome. The prophage shares most of its genes (30/33) with Helicobacter pylori prophage KHP30. Moreover, a 1,886 bp transposable sequence (IS605) was found in the prophage. Our results imply that the Naxi ethnic minority isolate YN4-84 and Han isolate YN1-91 belong to the hspEAsia subgroup and have diverse genome structure. The genome has been extensively modified in several regions involved in horizontal DNA transfer. The important roles played by phages in the ecology and microevolution of H. pylori were further emphasized. The current data will provide valuable information regarding the H. pylori genome based on historic human migrations and population structure.     

Genome of Helicobacter pylori strain 908

Helicobacter pylori is a genetically diverse and coevolved pathogen inhabiting human gastric niches and leading to a spectrum of gastric diseases in susceptible populations. We describe the genome sequence of H. pylori 908, which was originally isolated from an African patient living in France who suffered with recrudescent duodenal ulcer disease. The strain was found to be phylogenetically related to H. pylori J99, and its comparative analysis revealed several specific genome features and novel insertion-deletion and substitution events. The genome sequence revealed several strain-specific deletions and/or gain of genes exclusively present in HP908 compared with different sequenced genomes already available in the public domain. Comparative and functional genomics of HP908 and its subclones will be important in understanding genomic plasticity and the capacity to colonize and persist in a changing host environment.     

Comparative proteome analysis of Helicobacter pylori

Helicobacter pylori, the causative agent of gastritis, ulcer and stomach carcinoma, infects approximately half of the worlds population. After sequencing the complete genome of two strains, 26695 and J99, we have approached the demanding task of investigating the functional part of the genetic information containing macromolecules, the proteome. The proteins of three strains of H. pylori, 26695 and J99, and a prominent strain used in animal models SS1, were separated by a high-resolution two-dimensional electrophoresis technique with a resolution power of 5000 protein spots. Up to 1800 protein species were separated from H. pylori which had been cultivated for 5 days on agar plates. Using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) peptide mass fingerprinting we have identified 152 proteins, including nine known virulence factors and 28 antigens. The three strains investigated had only a few protein spots in common. We observe that proteins with an amino acid exchange resulting in a net change of only one charge are shifted in the two-dimensional electrophoresis (2-DE) pattern. The expression of 27 predicted conserved hypothetical open reading frames (ORFs) and six unknown ORFs were confirmed. The growth conditions of the bacteria were shown to have an effect on the presence of certain proteins. A preliminary immunoblotting study using human sera revealed that this approach is ideal for identifying proteins of diagnostic or therapeutic value. H. pylori 2-DE patterns with their identified protein species were added to the dynamic 2D-PAGE database (http://www.mpiib-berlin.mpg.de/2D-PAGE/). This basic knowledge of the proteome in the public domain will be an effective instrument for the identification of new virulence or pathogenic factors, and antigens of potentially diagnostic or curative value against H. pylori.     

Genome sequence of Helicobacter pylori hpEurope strain N6

Helicobacter pylori colonizes about half of the world's population. It is a causative agent of stomach diseases, including malignant tumors. We report the genome sequence of strain N6, which is widely used in H. pylori research and appreciated for its large cell size and high transformation efficiency.     

Sequence,Structural and Expression Divergence of Duplicate Genes in the Bovine Genome

Gene duplication is a widespread phenomenon in genome evolution, and it has been proposed to serve as an engine of evolutionary innovation. In the present study, we performed the first comprehensive analysis of duplicate genes in the bovine genome. A total of 3131 putative duplicated gene pairs were identified, including 712 cattle-specific duplicate gene pairs unevenly distributed across the genome, which are significantly enriched for specific biological functions including immunity, growth, digestion, reproduction, embryonic development, inflammatory response, and defense response to bacterium. Around 97.1% (87.8%) of (cattle-specific) duplicate gene pairs were found to have distinct exon-intron structures. Analysis of gene expression by RNA-Seq and sequence divergence (synonymous or non-synonymous) revealed that expression divergence is correlated with sequence divergence, as has been previously observed in other species. This analysis also led to the identification of a subset of cattle-specific duplicate gene pairs exhibiting very high expression divergence. Interestingly, further investigation revealed a significant relationship between structural and expression divergence while controlling for the effect of synonymous sequence divergence. Together these results provide further insight into duplicate gene sequence and expression divergence in cattle, and their potential contributions to phenotypic divergence.     

Comparative genome analysis of Helicobacter pylori strains

DNA macroarrays were used to characterize 17 Helicobacter pylori strains isolated in four geographic regions of Russia (Moscow, St. Petersburg, Kazan, and Novosibirsk). Of all genes, 1272 (81%) proved to occur in all strains and to constitute a functional core of the genome, and 293 (18.7%) were strain-specific and greatly varied among the H. pylori strains. Most (71%) of the latter had unknown functions; the remainder included restriction-modification genes (3-9%), transposition genes (2-4%), and genes coding for outer membrane proteins (2-4%). The Russian H. pylori strains did not differ in genome organization or in the number and distribution of strain-specific genes from strains isolated in other countries.     

Comparative Analysis of Different Typing Methods for Helicobacter pylori Clinical Isolates

The goal of the present work was to compare different techniques of molecular typing using as an example clinical isolates of Helicobacter pylori obtained from patients in different regions of Russia. DNA-macroarray genome scanning using individual genes was employed to set up our basic classification of isolates that did or did not contain pathogenicity islands. In parallel, DNA of the same isolates was used in the conventional random amplified polymorphic DNA (RAPD) PCR analysis, and the isolates were also genotyped (cagA, vacA, iceA, and babA status) and their proteomic maps were obtained by means of unidimensional SDS polyacrylamide gel electrophoresis (1D-SDS-PAGE) coupled with identification using peptide mass fingerprinting by MALDI-TOF mass spectrometry. A statistically significant correlation (coefficient of correlation r = 0.25, p = 0.005) was observed between the results of genome scanning and 1D-SDS-PAGE. No correlation was found between RAPD-PCR typing and genome scanning.     

Complete Genome Sequences of Two Helicobacter pylori Bacteriophages Isolated from Japanese Patients

Helicobacter pylori causes peptic ulcers and gastric cancer, which lead to significantly higher morbidity in Japan than elsewhere in the world. As bacteriophage (phage) and host bacteria coevolve, the study of H. pylori phages is important to extend understanding of the evolution and pathogenesis of H. pylori. Here we report two complete genome sequences of H. pylori phages KHP30 and KHP40, which were released spontaneously from the most pathogenic East Asian-type isolates from Japanese patients.     

Comparative Analysis between Homoeologous Genome Segments of Brassica napus and Its Progenitor Species Reveals Extensive Sequence-Level Divergence

Homoeologous regions of Brassica genomes were analyzed at the sequence level. These represent segments of the Brassica A genome as found in Brassica rapa and Brassica napus and the corresponding segments of the Brassica C genome as found in Brassica oleracea and B. napus. Analysis of synonymous base substitution rates within modeled genes revealed a relatively broad range of times (0.12 to 1.37 million years ago) since the divergence of orthologous genome segments as represented in B. napus and the diploid species. Similar, and consistent, ranges were also identified for single nucleotide polymorphism and insertion-deletion variation. Genes conserved across the Brassica genomes and the homoeologous segments of the genome of Arabidopsis thaliana showed almost perfect collinearity. Numerous examples of apparent transduplication of gene fragments, as previously reported in B. oleracea, were observed in B. rapa and B. napus, indicating that this phenomenon is widespread in Brassica species. In the majority of the regions studied, the C genome segments were expanded in size relative to their A genome counterparts. The considerable variation that we observed, even between the different versions of the same Brassica genome, for gene fragments and annotated putative genes suggest that the concept of the pan-genome might be particularly appropriate when considering Brassica genomes.     

番木瓜环斑病毒海南分离株全基因组序列分析

番木瓜环斑病毒(Papaya ringspot virus,PRSV)是马铃薯Y病毒属(genus Potyvirus)的成员之一.病毒粒体呈线状,长700～900nm,直径为12.5nm.为单分体正链RNA病毒,由多种蚜虫以非持久方式传播.依寄主范围可划分为P型和W型两种.其中P型株系(PRSV-P)是制约生产的重要病原,除了给番木瓜生产带来严重危害,也会危害葫芦科作物.W型株系(PRSV-W)是危害葫芦科作物的主要病原,虽然和PRSV-P型株系血清学反应密切相关,但不侵染番木瓜.