Comparative Genomics of Emerging Human Ehrlichiosis Agents

Anaplasma (formerly Ehrlichia) phagocytophilum, Ehrlichia chaffeensis, and Neorickettsia (formerly Ehrlichia) sennetsu are intracellular vector-borne pathogens that cause human ehrlichiosis, an emerging infectious disease. We present the complete genome sequences of these organisms along with comparisons to other organisms in the Rickettsiales order. Ehrlichia spp. and Anaplasma spp. display a unique large expansion of immunodominant outer membrane proteins facilitating antigenic variation. All Rickettsiales have a diminished ability to synthesize amino acids compared to their closest free-living relatives. Unlike members of the Rickettsiaceae family, these pathogenic Anaplasmataceae are capable of making all major vitamins, cofactors, and nucleotides, which could confer a beneficial role in the invertebrate vector or the vertebrate host. Further analysis identified proteins potentially involved in vacuole confinement of the Anaplasmataceae, a life cycle involving a hematophagous vector, vertebrate pathogenesis, human pathogenesis, and lack of transovarial transmission. These discoveries provide significant insights into the biology of these obligate intracellular pathogens

Whole genome shotgun sequencing of Brassica oleracea and its application to gene discovery and annotation in Arabidopsis

Through comparative studies of the model organism Arabidopsis thaliana and its close relative Brassica oleracea, we have identified conserved regions that represent potentially functional sequences overlooked by previous Arabidopsis genome annotation methods. A total of 454,274 whole genome shotgun sequences covering 283 Mb (0.44×) of the estimated 650 Mb Brassica genome were searched against the Arabidopsis genome, and conserved Arabidopsis genome sequences (CAGSs) were identified. Of these 229,735 conserved regions, 167,357 fell within or intersected existing gene models, while 60,378 were located in previously unannotated regions. After removal of sequences matching known proteins, CAGSs that were close to one another were chained together as potentially comprising portions of the same functional unit. This resulted in 27,347 chains of which 15,686 were sufficiently distant from existing gene annotations to be considered a novel conserved unit. Of 192 conserved regions examined, 58 were found to be expressed in our cDNA populations. Rapid amplification of cDNA ends (RACE) was used to obtain potentially full-length transcripts from these 58 regions. The resulting sequences led to the creation of 21 gene models at 17 new Arabidopsis loci and the addition of splice variants or updates to another 19 gene structures. In addition, CAGSs overlapping already annotated genes in Arabidopsis can provide guidance for manual improvement of existing gene models. Published genome-wide expression data based on whole genome tiling arrays and massively parallel signature sequencing were overlaid on the Brassica–Arabidopsis conserved sequences, and 1399 regions of intersection were identified. Collectively our results and these data sets suggest that several thousand new Arabidopsis genes remain to be identified and annotated

The complete genome sequence of the \u3ci\u3eArabidopsis\u3c/i\u3e and tomato pathogen \u3ci\u3ePseudomonas syringae\u3c/i\u3e pv. \u3ci\u3etomato\u3c/i\u3e DC3000

We report the complete genome sequence of the model bacterial pathogen Pseudomonas syringae pathovar tomato DC3000 (DC3000), which is pathogenic on tomato and Arabidopsis thaliana. The DC3000 genome (6.5 megabases) contains a circular chromosome and two plasmids, which collectively encode 5,763 ORFs. We identified 298 established and putative virulence genes, including several clusters of genes encoding 31 confirmed and 19 predicted type III secretion system effector proteins. Many of the virulence genes were members of paralogous families and also were proximal to mobile elements, which collectively comprise7%of the DC3000 genome. The bacterium possesses a large repertoire of transporters for the acquisition of nutrients, particularly sugars, as well as genes implicated in attachment to plant surfaces. Over 12% of the genes are dedicated to regulation, which may reflect the need for rapid adaptation to the diverse environments encountered during epiphytic growth and pathogenesis. Comparative analyses confirmed a high degree of similarity with two sequenced pseudomonads, Pseudomonas putida and Pseudomonas aeruginosa, yet revealed 1,159 genes unique to DC3000, of which 811 lack a known function. Includes published article and additional supporting materials

The complete genome sequence of the gastric pathogen Helicobacter pylori

Helicobacter pylori, strain 26695, has circular genome of 1,667,867 base pairs and 1,590 predicted coding sequences. Sequence analysis indicates that H. pylori has well-developed systems for motility, for scavenging iron, and for DNA restriction and modification. Many putative adhesins, lipoproteins and other outer membrane proteins were identified, underscoring the potential complexity of host-pathogen interaction. Based on the large number of sequence-related genes encoding outer membrane proteins and the presence of homopolymeric tracts and dinucleotide repeats in coding sequences, H. pylori, like several other mucosal pathogens, probably uses recombination and slipped-strand mispairing within repeats as mechanisms for antigenio variation and adaptive evolution. Consistent with its restricted niche, H. pylori has a few regulatory networks, and a limited metabolic repertoire and biosynthetic capacity. Its survival in acid conditions depends, in part, on its ability to establish a positive inside-membrane potential in low pH

Role of Mobile DNA in the Evolution of Vancomycin-Resistant Enterococcus faecalis

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Complete genome sequence of Caulobacter crescentus

The complete genome sequence of Caulobacter crescentus was determined to be 4,016,942 base pairs in a single circular chromosome encoding 3,767 genes. This organism, which grows in a dilute aquatic environment, coordinates the cell division cycle and multiple cell differentiation events. With the annotated genome sequence, a full description of the genetic network that controls bacterial differentiation, cell growth, and cell cycle progression is within reach. Two-component signal transduction proteins are known to play a significant role in cell cycle progression. Genome analysis revealed that the C. crescentus genome encodes a significantly higher number of these signaling proteins (105) than any bacterial genome sequenced thus far. Another regulatory mechanism involved in cell cycle progression is DNA methylation. The occurrence of the recognition sequence for an essential DNA methylating enzyme that is required for cell cycle regulation is severely limited and shows a bias to intergenic regions. The genome contains multiple clusters of genes encoding proteins essential for survival in a nutrient poor habitat. Included are those involved in chemotaxis, outer membrane channel function, degradation of aromatic ring compounds, and the breakdown of plant-derived carbon sources, in addition to many extracytoplasmic function sigma factors, providing the organism with the ability to respond to a wide range of environmental fluctuations. C. crescentus is, to our knowledge, the first free-living α-class proteobacterium to be sequenced and will serve as a foundation for exploring the biology of this group of bacteria, which includes the obligate endosymbiont and human pathogen Rickettsia prowazekii, the plant pathogen Agrobacterium tumefaciens, and the bovine and human pathogen Brucella abortus

Genomic insights into methanotrophy: The complete genome sequence of Methylococcus capsulatus (Bath)

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The sequence and analysis of Trypanosoma brucei chromosome II

We report here the sequence of chromosome II from Trypanosoma brucei, the causative agent of African sleeping sickness. The 1.2-Mb pairs encode about 470 predicted genes organised in 17 directional clusters on either strand, the largest cluster of which has 92 genes lined up over a 284-kb region. An analysis of the GC skew reveals strand compositional asymmetries that coincide with the distribution of protein-coding genes, suggesting these asymmetries may be the result of transcription-coupled repair on coding versus non-coding strand. A 5-cM genetic map of the chromosome reveals recombinational ‘hot’ and ‘cold’ regions, the latter of which is predicted to include the putative centromere. One end of the chromosome consists of a 250-kb region almost exclusively composed of RHS (pseudo)genes that belong to a newly characterised multigene family containing a hot spot of insertion for retroelements. Interspersed with the RHS genes are a few copies of truncated RNA polymerase pseudogenes as well as expression site associated (pseudo)genes (ESAGs) 3 and 4, and 76 bp repeats. These features are reminiscent of a vestigial variant surface glycoprotein (VSG) gene expression site. The other end of the chromosome contains a 30-kb array of VSG genes, the majority of which are pseudogenes, suggesting that this region may be a site for modular de novo construction of VSG gene diversity during transposition/gene conversion events