The impact of comparative genomics on infectious disease research

CoryneBase: Corynebacterium genomic resources and analysis tools at your fingertips

Corynebacteria are used for a wide variety of industrial purposes but some species are associated with human diseases. With increasing number of corynebacterial genomes having been sequenced, comparative analysis of these strains may provide better understanding of their biology, phylogeny, virulence and taxonomy that may lead to the discoveries of beneficial industrial strains or contribute to better management of diseases. To facilitate the ongoing research of corynebacteria, a specialized central repository and analysis platform for the corynebacterial research community is needed to host the fast-growing amount of genomic data and facilitate the analysis of these data. Here we present CoryneBase, a genomic database for Corynebacterium with diverse functionality for the analysis of genomes aimed to provide: (1) annotated genome sequences of Corynebacterium where 165,918 coding sequences and 4,180 RNAs can be found in 27 species; (2) access to comprehensive Corynebacterium data through the use of advanced web technologies for interactive web interfaces; and (3) advanced bioinformatic analysis tools consisting of standard BLAST for homology search, VFDB BLAST for sequence homology search against the Virulence Factor Database (VFDB), Pairwise Genome Comparison (PGC) tool for comparative genomic analysis, and a newly designed Pathogenomics Profiling Tool (PathoProT) for comparative pathogenomic analysis. CoryneBase offers the access of a range of Corynebacterium genomic resources as well as analysis tools for comparative genomics and pathogenomics. It is publicly available at http://corynebacterium.um.edu.my/.

Realities and expectations of pharmacogenomics and personalized medicine: impact of translating genetic knowledge into clinical practice

The implementation of genetic data for a better prediction of response to medications and adverse drug reactions is becoming a reality in some clinical fields. However, to be successful, personalized medicine should take advantage of an informational structured framework of genetic, phenotypic and environmental factors in order to provide the healthcare system with useful tools that can optimize the effectiveness of specific treatment. The impact of personalized medicine is potentially enormous, but the results that have so far been gathered are often difficult to translate into clinical practice. In this article we have summarized the most relevant applications of pharmacogenomics on diseases to which they have already been applied and fields in which they are currently emerging. The article provides an overview of the opportunities and shortcomings of the implementation of genetic information into personalized medicine and its full adoption in the clinic. In the second instance, it provides readers from different fields of expertise with an accessible interpretation to the barriers and opportunities in the use/adoption of pharmacogenomic testing between the different clinical areas.

Accurate localization of the integration sites of two genomic islands at single-nucleotide resolution in the genome of Bacillus cereus ATCC 10987

We have identified two genomic islands, that is, BCEGI-1 and BCEGI-2, in the genome of Bacillus cereus ATCC 10987, based on comparative analysis with Bacillus cereus ATCC 14579. Furthermore, by using the cumulative GC profile and performing homology searches between the two genomes, the integration sites of the two genomic islands were determined at single-nucleotide resolution. BCEGI-1 is integrated between 159705 bp and 198000 bp, whereas BCEGI-2 is integrated between the end of ORF BCE4594 and the start of the intergenic sequence immediately following BCE4626, that is, from 4256803 bp to 4285534 bp. BCEGI-1 harbors two bacterial Tn7 transposons, which have two sets of genes encoding TnsA, B, C, and D. It is generally believed that unlike the TnsABC+E pathway, the TnsABC+D pathway would only promote vertical transmission to daughter cells. The evidence presented in this paper, however, suggests a role of the TnsABC+D pathway in the horizontal transfer of some genomic islands.

Analysis of the genome content of Lactococcus garvieae by genomic interspecies microarray hybridization

Background

Lactococcus garvieae is a bacterial pathogen that affects different animal species in addition to humans. Despite the widespread distribution and emerging clinical significance of L. garvieae in both veterinary and human medicine, there is almost a complete lack of knowledge about the genetic content of this microorganism. In the present study, the genomic content of L. garvieae CECT 4531 was analysed using bioinformatics tools and microarray-based comparative genomic hybridization (CGH) experiments. Lactococcus lactis subsp. lactis IL1403 and Streptococcus pneumoniae TIGR4 were used as reference microorganisms.

Results

The combination and integration of in silico analyses and in vitro CGH experiments, performed in comparison with the reference microorganisms, allowed establishment of an inter-species hybridization framework with a detection threshold based on a sequence similarity of ≥ 70%. With this threshold value, 267 genes were identified as having an analogue in L. garvieae, most of which (n = 258) have been documented for the first time in this pathogen. Most of the genes are related to ribosomal, sugar metabolism or energy conversion systems. Some of the identified genes, such as als and mycA, could be involved in the pathogenesis of L. garvieae infections.

Conclusions

In this study, we identified 267 genes that were potentially present in L. garvieae CECT 4531. Some of the identified genes could be involved in the pathogenesis of L. garvieae infections. These results provide the first insight into the genome content of L. garvieae.

Genomic Approaches to the Host Response to Pathogens

The need to better understand host–pathogen interactions has risen with the expansion in genomics and related technologies. This chapter focuses on two aspects of the host response to pathogens where major advances are being made using genomic approaches. The availability of complete genomic sequences of an expanding number of pathogens, the human and mouse genome sequences, and the advent of genome-wide genotyping and gene expression profiling has opened up new avenues of investigation in the field. The genotype of the pathogen plays a major role in the response of the host to infection with more virulent pathogenic strains possessing the capability to interfere with the host immune response. In addition, different individuals in a population can have very different responses to a genetically identical pathogen. Part of the differential response is governed by the underlying genetic differences between individuals. The advent of genome-wide genotyping using single nucleotide polymorphisms or microsatellite markers is leading to major advances in molecular epidemiology. The future impact of genomic approaches on the development of diagnostics and therapeutics is discussed for infectious diseases. This includes defining the basis of genetic susceptibility to infection and system-wide molecular response to a pathogen.

The association of virulence factors with genomic islands

BACKGROUND

It has been noted that many bacterial virulence factor genes are located within genomic islands (GIs; clusters of genes in a prokaryotic genome of probable horizontal origin). However, such studies have been limited to single genera or isolated observations. We have performed the first large-scale analysis of multiple diverse pathogens to examine this association. We additionally identified genes found predominantly in pathogens, but not non-pathogens, across multiple genera using 631 complete bacterial genomes, and we identified common trends in virulence for genes in GIs. Furthermore, we examined the relationship between GIs and clustered regularly interspaced palindromic repeats (CRISPRs) proposed to confer resistance to phage.

METHODOLOGY/PRINCIPAL FINDINGS

We show quantitatively that GIs disproportionately contain more virulence factors than the rest of a given genome (p<1E-40 using three GI datasets) and that CRISPRs are also over-represented in GIs. Virulence factors in GIs and pathogen-associated virulence factors are enriched for proteins having more "offensive" functions, e.g. active invasion of the host, and are disproportionately components of type III/IV secretion systems or toxins. Numerous hypothetical pathogen-associated genes were identified, meriting further study.

CONCLUSIONS/SIGNIFICANCE

This is the first systematic analysis across diverse genera indicating that virulence factors are disproportionately associated with GIs. "Offensive" virulence factors, as opposed to host-interaction factors, may more often be a recently acquired trait (on an evolutionary time scale detected by GI analysis). Newly identified pathogen-associated genes warrant further study. We discuss the implications of these results, which cement the significant role of GIs in the evolution of many pathogens.

The use of genomics in microbial vaccine development

Vaccination is one of the most effective tools for the prevention of infectious diseases. The availability of complete genome sequences, together with the progression of high-throughput technologies such as functional and structural genomics, has led to a new paradigm in vaccine development. Pan-genomic reverse vaccinology, with the comparison of sequence data from multiple isolates of the same species of a pathogen, increases the opportunity of the identification of novel vaccine candidates. Overall, the conventional empiric approach to vaccine development is being replaced by vaccine design. The recent development of synthetic genomics may provide a further opportunity to design vaccines.

A combined computational-experimental analyses of selected metabolic enzymes in Pseudomonas species

Comparative genomic analysis has revolutionized our ability to predict the metabolic subsystems that occur in newly sequenced genomes, and to explore the functional roles of the set of genes within each subsystem. These computational predictions can considerably reduce the volume of experimental studies required to assess basic metabolic properties of multiple bacterial species. However, experimental validations are still required to resolve the apparent inconsistencies in the predictions by multiple resources. Here, we present combined computational-experimental analyses on eight completely sequenced Pseudomonas species. Comparative pathway analyses reveal that several pathways within the Pseudomonas species show high plasticity and versatility. Potential bypasses in 11 metabolic pathways were identified. We further confirmed the presence of the enzyme O-acetyl homoserine (thiol) lyase (EC: 2.5.1.49) in P. syringae pv. tomato that revealed inconsistent annotations in KEGG and in the recently published SYSTOMONAS database. These analyses connect and integrate systematic data generation, computational data interpretation, and experimental validation and represent a synergistic and powerful means for conducting biological research.

Genome-wide analysis of ruminant Staphylococcus aureus reveals diversification of the core genome

Staphylococcus aureus causes disease in humans and a wide array of animals. Of note, S. aureus mastitis of ruminants, including cows, sheep, and goats, results in major economic losses worldwide. Extensive variation in genome content exists among S. aureus pathogenic clones. However, the genomic variation among S. aureus strains infecting different animal species has not been well examined. To investigate variation in the genome content of human and ruminant S. aureus, we carried out whole-genome PCR scanning (WGPS), comparative genomic hybridizations (CGH), and the directed DNA sequence analysis of strains of human, bovine, ovine, and caprine origin. Extensive variation in genome content was discovered, including host- and ruminant-specific genetic loci. Ovine and caprine strains were genetically allied, whereas bovine strains were heterogeneous in gene content. As expected, mobile genetic elements such as pathogenicity islands and bacteriophages contributed to the variation in genome content between strains. However, differences specific for ruminant strains were restricted to regions of the conserved core genome, which contained allelic variation in genes encoding proteins of known and unknown function. Many of these proteins are predicted to be exported and could play a role in host-pathogen interactions. The genomic regions of difference identified by the whole-genome approaches adopted in the current study represent excellent targets for studies of the molecular basis of S. aureus host adaptation.

Novel Genetic Techniques and Approaches in the Microbial Genomics Era

The availability of microbial genome sequences has ushered in the genomics era and has led to numerous technical advancements over the past decade. These advances have been both in the bioinformatics field that has integrated computer-based approaches with biology and in research methods in the laboratory. The advances have assisted scientists in their study of bacterial gene complements and the roles of their gene products in the bacterial life cycle. Assignment of genes as essential to the bacterial cell nominated them as potential targets for antibacterial drugs and spurred attempts to exploit this information and convert it into drugs. At present, these efforts have met with minimal success. There are several possible reasons for these disappointing results including choice of targets and screen designs, compound libraries chosen for screens, and decreased commitment to antibacterial drug discovery by many large pharmaceutical companies. Structure-based approaches could become very effective in the future as methodologies continue to improve.