Dataset Information

An automated approach for the identification of horizontal gene transfers from complete genomes reveals the rhizome of Rickettsiales.

ABSTRACT:

Background

Horizontal gene transfer (HGT) is considered to be a major force driving the evolutionary history of prokaryotes. HGT is widespread in prokaryotes, contributing to the genomic repertoire of prokaryotic organisms, and is particularly apparent in Rickettsiales genomes. Gene gains from both distantly and closely related organisms play crucial roles in the evolution of bacterial genomes. In this work, we focus on genes transferred from distantly related species into Rickettsiales species.

Results

We developed an automated approach for the detection of HGT from other organisms (excluding alphaproteobacteria) into Rickettsiales genomes. Our systematic approach consisted of several specialized features including the application of a parsimony method for inferring phyletic patterns followed by blast filter, automated phylogenetic reconstruction and the application of patterns for HGT detection. We identified 42 instances of HGT in 31 complete Rickettsiales genomes, of which 38 were previously unidentified instances of HGT from Anaplasma, Wolbachia, Candidatus Pelagibacter ubique and Rickettsia genomes. Additionally, putative cases with no phylogenetic support were assigned gene ontology terms. Overall, these transfers could be characterized as "rhizome-like".

Conclusions

Our analysis provides a comprehensive, systematic approach for the automated detection of HGTs from several complete proteome sequences that can be applied to detect instances of HGT within other genomes of interest.

SUBMITTER: Le PT

PROVIDER: S-EPMC3575314 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Publications

An automated approach for the identification of horizontal gene transfers from complete genomes reveals the rhizome of Rickettsiales.

Le Phuong Thi PT Ramulu Hemalatha Golaconda HG Guijarro Laurent L Paganini Julien J Gouret Philippe P Chabrol Olivier O Raoult Dider D Pontarotti Pierre P

BMC evolutionary biology 20121212

<h4>Background</h4>Horizontal gene transfer (HGT) is considered to be a major force driving the evolutionary history of prokaryotes. HGT is widespread in prokaryotes, contributing to the genomic repertoire of prokaryotic organisms, and is particularly apparent in Rickettsiales genomes. Gene gains from both distantly and closely related organisms play crucial roles in the evolution of bacterial genomes. In this work, we focus on genes transferred from distantly related species into Rickettsiales ...[more]

PMID: 23234643

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Project description:BACKGROUND: First pass methods based on BLAST match are commonly used as an initial step to separate the different phylogenetic histories of genes in microbial genomes, and target putative horizontal gene transfer (HGT) events. This will continue to be necessary given the rapid growth of genomic data and the technical difficulties in conducting large-scale explicit phylogenetic analyses. However, these methods often produce misleading results due to their inability to resolve indirect phylogenetic links and their vulnerability to stochastic events. RESULTS: A new computational method of rapid, exhaustive and genome-wide detection of HGT was developed, featuring the systematic analysis of BLAST hit distribution patterns in the context of a priori defined hierarchical evolutionary categories. Genes that fall beyond a series of statistically determined thresholds are identified as not adhering to the typical vertical history of the organisms in question, but instead having a putative horizontal origin. Tests on simulated genomic data suggest that this approach effectively targets atypically distributed genes that are highly likely to be HGT-derived, and exhibits robust performance compared to conventional BLAST-based approaches. This method was further tested on real genomic datasets, including Rickettsia genomes, and was compared to previous studies. Results show consistency with currently employed categories of HGT prediction methods. In-depth analysis of both simulated and real genomic data suggests that the method is notably insensitive to stochastic events such as gene loss, rate variation and database error, which are common challenges to the current methodology. An automated pipeline was created to implement this approach and was made publicly available at: https://github.com/DittmarLab/HGTector. The program is versatile, easily deployed, has a low requirement for computational resources. CONCLUSIONS: HGTector is an effective tool for initial or standalone large-scale discovery of candidate HGT-derived genes.

Project description:The extent of horizontal gene transfer (HGT) among marine pelagic prokaryotes and the role that HGT may have played in their adaptation to this particular environment remain open questions. This is partly due to the paucity of cultured species and genomic information for many widespread groups of marine bacteria and archaea. Molecular studies have revealed a large diversity and relative abundance of marine planktonic archaea, in particular of Thaumarchaeota (also known as group I Crenarchaeota) and Euryarchaeota of groups II and III, but only one species (the thaumarchaeote Candidatus Nitrosopumilus maritimus) has been isolated in pure culture so far. Therefore, metagenomics remains the most powerful approach to study these environmental groups. To investigate the impact of HGT in marine archaea, we carried out detailed phylogenetic analyses of all open reading frames of 21 archaeal 16S rRNA gene-containing fosmids and, to extend our analysis to other genomic regions, also of fosmid-end sequences of 12 774 fosmids from three different deep-sea locations (South Atlantic and Adriatic Sea at 1000 m depth, and Ionian Sea at 3000 m depth). We found high HGT rates in both marine planktonic Thaumarchaeota and Euryarchaeota, with remarkable converging values estimated from complete-fosmid and fosmid-end sequence analysis (25 and 21% of the genes, respectively). Most HGTs came from bacterial donors (mainly from Proteobacteria, Firmicutes and Chloroflexi) but also from other archaea and eukaryotes. Phylogenetic analyses showed that in most cases HGTs are shared by several representatives of the studied groups, implying that they are ancient and have been conserved over relatively long evolutionary periods. This, together with the functions carried out by these acquired genes (mostly related to energy metabolism and transport of metabolites across membranes), suggests that HGT has played an important role in the adaptation of these archaea to the cold and nutrient-depleted deep marine environment.

Dataset Information

An automated approach for the identification of horizontal gene transfers from complete genomes reveals the rhizome of Rickettsiales.

Background

Results

Conclusions

Publications

An automated approach for the identification of horizontal gene transfers from complete genomes reveals the rhizome of Rickettsiales.

Similar Datasets

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