Research in the genomic sciences is confronted with the volume of sequencing and resequencing data increasing at a higher pace than that of data storage and communication resources, shifting a significant part of research budgets from the sequencing component of a project to the computational one. Hence, being able to efficiently store sequencing and resequencing data is a problem of paramount importance. In this article, we describe GReEn (Genome Resequencing Encoding), a tool for compressing genome resequencing data using a reference genome sequence. It overcomes some drawbacks of the recently proposed tool GRS, namely, the possibility of compressing sequences that cannot be handled by GRS, faster running times and compression gains of over 100-fold for some sequences. This tool is freely available for non-commercial use at ftp://ftp.ieeta.pt/∼ap/codecs/GReEn1.tar.gz.

Motivation: The data deluge phenomenon is becoming a serious problem in most genomic centers. To alleviate it, general purpose tools, such as gzip, are used to compress the data. However, although pervasive and easy to use, these tools fall short when the intention is to reduce as much as possible the data, for example, for medium- and long-term storage. A number of algorithms have been proposed for the compression of genomics data, but unfortunately only a few of them have been made available as usable and reliable compression tools.Results: In this article, we describe one such tool, MFCompress, specially designed for the compression of FASTA and multi-FASTA files. In comparison to gzip and applied to multi-FASTA files, MFCompress can provide additional average compression gains of almost 50%, i.e. it potentially doubles the available storage, although at the cost of some more computation time. On highly redundant datasets, and in comparison with gzip, 8-fold size reductions have been obtained.Availability: Both source code and binaries for several operating systems are freely available for non-commercial use at http://bioinformatics.ua.pt/software/mfcompress/.Contact: ap@ua.ptSupplementary information: Supplementary data are available at Bioinformatics online.

Abstract:The ever increasing growth of the production of high-throughput sequencing data poses a serious challenge to the storage, processing and transmission of these data. As frequently stated, it is a data deluge. Compression is essential to address this challenge-it reduces storage space and processing costs, along with speeding up data transmission. In this paper, we provide a comprehensive survey of existing compression approaches, that are specialized for biological data, including protein and DNA sequences. Also, we devote an important part of the paper to the approaches proposed for the compression of different file formats, such as FASTA, as well as FASTQ and SAM/BAM, which contain quality scores and metadata, in addition to the biological sequences. Then, we present a comparison of the performance of several methods, in terms of compression ratio, memory usage and compression/decompression time. Finally, we present some suggestions for future research on biological data compression.

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Motivation: Ebola virus causes high mortality hemorrhagic fevers, with more than 25 000 cases and 10 000 deaths in the current outbreak. Only experimental therapies are available, thus, novel diagnosis tools and druggable targets are needed.Results: Analysis of Ebola virus genomes from the current outbreak reveals the presence of short DNA sequences that appear nowhere in the human genome. We identify the shortest such sequences with lengths between 12 and 14. Only three absent sequences of length 12 exist and they consistently appear at the same location on two of the Ebola virus proteins, in all Ebola virus genomes, but nowhere in the human genome. The alignment-free method used is able to identify pathogen-specific signatures for quick and precise action against infectious agents, of which the current Ebola virus outbreak provides a compelling example.Availability and Implementation: EAGLE is freely available for non-commercial purposes at http://bioinformatics.ua.pt/software/eagle.Contact: raquelsilva@ua.pt; pratas@ua.ptSupplementary Information: Supplementary data are available at Bioinformatics online.

The ability of finite-context models for compressing DNA sequences has been demonstrated on some recent works. In this paper, we further explore this line, proposing a compression method based on eight finite-context models, with orders from two to sixteen, whose probabilities are averaged using weights calculated through a recursive procedure. The method was tested on a total of 2,338 sequences belonging to bacterial genomes, with sizes ranging from 1,286 to 13,033,779 bases, showing better compression results than the state-of-the-art XM DNA coding algorithm and also faster operation.

The imprints left by persistent DNA viruses in the tissues can testify to the changes driving virus evolution as well as provide clues on the provenance of modern and ancient humans. However, the history hidden in skeletal remains is practically unknown, as only parvovirus B19 and hepatitis B virus DNA have been detected in hard tissues so far. Here, we investigated the DNA prevalences of 38 viruses in femoral bone of recently deceased individuals. To this end, we used quantitative PCRs and a custom viral targeted enrichment followed by next-generation sequencing. The data was analyzed with a tailor-made bioinformatics pipeline. Our findings revealed bone to be a much richer source of persistent DNA viruses than earlier perceived, discovering ten additional ones, including several members of the herpes-and polyomavirus families, as well as human papillomavirus 31 and torque teno virus. Remarkably, many of the viruses found have oncogenic potential and/or are likely to reactivate in the elderly and immunosuppressed individuals. Thus, their persistence warrants careful evaluation of their clinical significance and impact on bone biology. Our findings open new frontiers for the study of virus evolution from ancient relics as well as provide new tools for the investigation of human skeletal remains in forensic and archeological contexts.

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