More Than 99 Percent of the Microbes Inside Human are Unknown to Science

저자：   업로드：2017-08-25  조회수：

    A new survey of DNA fragments circulating in human blood suggests our bodies contain vastly more diverse microbes than anyone previously understood. What's more, the overwhelming majority of those microbes have never been seen before, let alone classified and named.

    The new survey, which effectively enabled sampling of the whole body, was undertaken by scientists based at Stanford University. These scientists report that by conducting a microbiome census that included both well-studied and previously ignored niches, they were able to show that our bodies contain vastly more diverse microbes than anyone previously understood. What's more, the overwhelming majority of those microbes have never been seen before, let alone classified and named.

    Survey details appeared in the Proceedings of the National Academy of Sciences, in an article entitled “Numerous Uncharacterized and Highly Divergent Microbes Which Colonize Humans Are Revealed by Circulating Cell-Free DNA.” The article describes the Stanford team’s survey technique - massive shotgun sequencing - as well as the scope of sample collection, 1351 blood draws from 188 patients.

    After subjecting the samples to shotgun sequencing, the Stanford team assembled 7190 contiguous regions (contigs) larger than 1 kbp, of which 3761 are novel. According to the scientists, the novel contigs had little or no sequence homology in any existing database.

    “The vast majority of these novel contigs possess coding sequences, and we have validated their existence both by finding their presence in independent experiments and by performing direct PCR amplification,” wrote the authors of the PNAS article. “When their nearest neighbors are located in the tree of life, many of the organisms represent entirely novel taxa, showing that microbial diversity within the human body is substantially broader than previously appreciated.”

    "We found the gamut," said Stephen Quake, Ph.D., a professor of bioengineering and applied physics, a member of Stanford Bio-X and the paper's senior author. "We found things that are related to things people have seen before, we found things that are divergent, and we found things that are completely novel."

    Of all the nonhuman DNA fragments the team gathered, 99% of them failed to match anything in existing genetic databases the researchers examined.

    With that in mind, Mark Kowarsk

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