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Gut bug genomes sequenced

8 March 2010
Appeared in BioNews 548

Scientists have catalogued the genes of microbes living in our gut, information that could be crucial in assessing the impact of microbes on our health. The study, published in Nature, reports the sequencing of 3.3 million microbial genes, a gene set around 150 times larger than the human genome.

The study, by European and Chinese scientists, was 'an amazing feat of data processing', according to Professor Elaine Holmes from Imperial College, London, who was not involved in the research. 'It's basically the biggest sequencing exercise anyone has done so far - it's about 200 times the sequencing effort of the Human Genome Project', said Dr Jeroen Raes of Vrije University in Brussels, a member of the international team.

Scientists from the European MetaHIT (Metagenomics of the Human Intestinal Tract) consortium and the Beijing Genomics Institute in China analysed faecal samples from 124 European adults, including healthy, overweight, obese and bowel disease patients.

This metagenomic approach - taking samples directly from the environment being studied because they are not easily cultured in laboratories - is traditionally challenging, according to Medical News Today. So many genes must be sequenced that it's hard to do quickly. The researchers overcame this by using a high-throughput Illumina genetic sequencer. This is the first time a metagenomics study has used Illumina, according to press reports, as it was previously thought unfeasible.

The sequenced genomes from the samples were compared to known sequences stored in reference databases and the ones known to belong to the human genome were excluded. Around 1,000 to 1,500 bacterial species were found in all 124 adults with each individual carrying 160 of the species. A high proportion, 40 per cent, of these was shared by at least half of the study participants.

The team hope their gut flora gene catalogue will be used as a reference point for future investigations into the genetic links between gut bacteria, lifestyle, including diet, and particular diseases such as Crohn's disease. 'Knowing which combination of genes is necessary for the right balance of microbes to thrive within our gut may allow us to use stool samples, which are non-invasive, as a measure of health', study co-author Dr Peer Bork told the media.

Dr Bork is senior scientist and joint group leader of the Structural and Computational Biology Unit at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, one of MetaHIT research centres.

SOURCES & REFERENCES
A human gut microbial gene catalogue established by metagenomic sequencing
Nature |  4 March 2010
Gut Flora Genes Dwarf Human Genome
Medical News Today |  5 March 2010
Human gut microbes hold 'second genome'
BBC News |  3 March 2010
Revealed: the 160 species living inside our guts
Independent |  4 March 2010
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