正當(dāng)物理學(xué)家苦苦尋找宇宙暗物質(zhì)之際，美國研究人員6月10日報告說,，他們完成了對“生命暗物質(zhì)”的基因組測序,。
1996年，科學(xué)家首次發(fā)現(xiàn)了一種名為“候選門TM6”的細菌,。這種細菌廣泛存在于水環(huán)境中,，卻無法在實驗室中培養(yǎng)，除了其標(biāo)志性的16S基因外,，科學(xué)界對它的生命活動特點幾乎一無所知,。正因此，“候選門TM6”細菌被稱為“生命暗物質(zhì)”,。
美國克雷格·文特爾研究所的研究人員在新一期美國《國家科學(xué)院學(xué)報》報告說,，他們采用能從單個細胞中捕獲基因組的自動化技術(shù)，從一家醫(yī)院休息室的水槽下水管生物膜上收集了TM6細菌,，并使用DNA（脫氧核糖核酸）拼接方法成功重建了該細菌的基因組,。
測序結(jié)果表明，這種細菌無法制造氨基酸,，可能需要寄居在生物膜中或者單細胞微生物內(nèi)部,。不過，目前尚不清楚TM6細菌對人體是否有害,。
研究人員表示,，該研究成果或?qū)⒂兄谂囵B(yǎng)和研究類似微生物，從而進一步了解它們的生態(tài)特征和功能,。（生物谷Bioon.com）
生物谷推薦英文摘要：
Proceedings of the National Academy of Sciences DOI：10.1073/pnas.1219809110
Candidate phylum TM6 genome recovered from a hospital sink biofilm provides genomic insights into this uncultivated phylum
Jeffrey S. McLeana,b,1, Mary-Jane Lombardoa, Jonathan H. Badgera, Anna Edlunda, Mark Novotnya, Joyclyn Yee-Greenbauma, Nikolay Vyahhic, Adam P. Halla, Youngik Yanga, Christopher L. Duponta, Michael G. Zieglerd, Hamidreza Chitsaze, Andrew E. Allena, Shibu Yoosepha, Glenn Teslerf, Pavel A. Pevznerc,g, Robert M. Friedmana, Kenneth H. Nealsona,b, J. Craig Ventera, and Roger S. Laskena
The “dark matter of life” describes microbes and even entire divisions of bacterial phyla that have evaded cultivation and have yet to be sequenced. We present a genome from the globally distributed but elusive candidate phylum TM6 and uncover its metabolic potential. TM6 was detected in a biofilm from a sink drain within a hospital restroom by analyzing cells using a highly automated single-cell genomics platform. We developed an approach for increasing throughput and effectively improving the likelihood of sampling rare events based on forming small random pools of single-flow–sorted cells, amplifying their DNA by multiple displacement amplification and sequencing all cells in the pool, creating a “mini-metagenome.” A recently developed single-cell assembler, SPAdes, in combination with contig binning methods, allowed the reconstruction of genomes from these mini-metagenomes. A total of 1.07 Mb was recovered in seven contigs for this member of TM6 (JCVI TM6SC1), estimated to represent 90% of its genome. High nucleotide identity between a total of three TM6 genome drafts generated from pools that were independently captured, amplified, and assembled provided strong confirmation of a correct genomic sequence. TM6 is likely a Gram-negative organism and possibly a symbiont of an unknown host (nonfree living) in part based on its small genome, low-GC content, and lack of biosynthesis pathways for most amino acids and vitamins. Phylogenomic analysis of conserved single-copy genes confirms that TM6SC1 is a deeply branching phylum.
