Complete genome sequence of Haemophilus parasuis SH0165

DraGnET: software for storing, managing and analyzing annotated draft genome sequence data

Background

New "next generation" DNA sequencing technologies offer individual researchers the ability to rapidly generate large amounts of genome sequence data at dramatically reduced costs. As a result, a need has arisen for new software tools for storage, management and analysis of genome sequence data. Although bioinformatic tools are available for the analysis and management of genome sequences, limitations still remain. For example, restrictions on the submission of data and use of these tools may be imposed, thereby making them unsuitable for sequencing projects that need to remain in-house or proprietary during their initial stages. Furthermore, the availability and use of next generation sequencing in industrial, governmental and academic environments requires biologist to have access to computational support for the curation and analysis of the data generated; however, this type of support is not always immediately available.

Results

To address these limitations, we have developed DraGnET (Draft Genome Evaluation Tool). DraGnET is an open source web application which allows researchers, with no experience in programming and database management, to setup their own in-house projects for storing, retrieving, organizing and managing annotated draft and complete genome sequence data. The software provides a web interface for the use of BLAST, allowing users to perform preliminary comparative analysis among multiple genomes. We demonstrate the utility of DraGnET for performing comparative genomics on closely related bacterial strains. Furthermore, DraGnET can be further developed to incorporate additional tools for more sophisticated analyses.

Conclusions

DraGnET is designed for use either by individual researchers or as a collaborative tool available through Internet (or Intranet) deployment. For genome projects that require genome sequencing data to initially remain proprietary, DraGnET provides the means for researchers to keep their data in-house for analysis using local programs or until it is made publicly available, at which point it may be uploaded to additional analysis software applications. The DraGnET home page is available at http://www.dragnet.cvm.iastate.edu and includes example files for examining the functionalities, a link for downloading the DraGnET setup package and a link to the DraGnET source code hosted with full documentation on SourceForge.

Identification of putative virulence-associated genes of Haemophilus parasuis through suppression subtractive hybridization

Haemophilus parasuis is the causative agent of Glässer's disease. Up to now 15 serovars of H. parasuis have been identified, with significant differences existing in virulence between serovars. In this study, suppression subtractive hybridization (SSH) was used to identify the genetic difference between Nagasaki (H. parasuis serovar 5 reference strain, highly virulent) and SW114 (H. parasuis serovar 3 reference strain, non-virulent). A total of 191 clones were obtained from the SSH library. Using dot hybridization and PCR, 15 clones were identified containing fragments that were present in the Nagasaki genome while absent in the SW114 genome. Among these 15 fragments, three fragments (ssh1, ssh13, ssh15) encode cell surface-associated components; three fragments (ssh2, ssh5, ssh9) are associated with metabolism and stress response; one fragment (ssh8) is involved in assembly of fimbria and one fragment (ssh6) is a phage phi-105 ORF25-like protein. The remaining seven fragments are hypothetical proteins or unknown. Based on PCR analysis of the 15 serovar reference strains, eight fragments (ssh1, ssh2, ssh3, ssh6, ssh8, ssh10, ssh11 and ssh12) were found in three to five of most virulent serovars (1, 5, 10, 12, 13 and 14), zero to two in three moderately virulent serovars (2, 4 and 15), but absent in the low virulent serovar (8) and non-virulent serovars (3, 6, 7, 9 and 11). In vivo transcription fragments ssh1, ssh2, ssh8 and ssh12 were identified in total RNA samples extracted from experimental infected pig lung by RT-PCR. This study has provided some evidence of genetic differences between H. parasuis strains of different virulence.

Characterization and comparative analysis of the genes encoding Haemophilus parasuis outer membrane proteins P2 and P5

Haemophilus parasuis is a swine pathogen of significant industry concern, but little is known about how the organism causes disease. A related human pathogen, Haemophilus influenzae, has been better studied, and many of its virulence factors have been identified. Two of these, outer membrane proteins P2 and P5, are known to have important virulence properties. The goals of this study were to identify, analyze, and compare the genetic relatedness of orthologous genes encoding P2 and P5 proteins in a diverse group of 35 H. parasuis strains. Genes encoding P2 and P5 proteins were detected in all H. parasuis strains evaluated. The predicted amino acid sequences for both P2 and P5 proteins exhibit considerable heterogeneity, particularly in regions corresponding to predicted extracellular loops. Twenty-five variants of P2 and 17 variants of P5 were identified. The P2 proteins of seven strains were predicted to contain a highly conserved additional extracellular loop compared to the remaining strains and to H. influenzae P2. Antigenic-site predictions coincided with predicted extracellular loop regions of both P2 and P5. Neighbor-joining trees constructed using P2 and P5 sequences predicted divergent evolutionary histories distinct from those predicted by a multilocus sequence typing phylogeny based on partial sequencing of seven housekeeping genes. Real-time reverse transcription-PCR indicated that both genes are expressed in all of the strains.