據(jù)每日科學(xué)網(wǎng)日前報(bào)道,，美國(guó)研究人員發(fā)現(xiàn)，線粒體與豐富的海洋細(xì)菌SAR11享有共同的進(jìn)化祖先,，這為研究線粒體這種十分重要的細(xì)胞器的起源提供了重要證據(jù),。
線粒體在形態(tài)、染色反應(yīng),、化學(xué)組成,、物理性質(zhì)、活動(dòng)狀態(tài),、遺傳體系等方面都很像細(xì)菌,，所以人們推測(cè)，需氧細(xì)菌被原始真核細(xì)胞吞噬后,，在長(zhǎng)期互利共生中演化形成了現(xiàn)在的線粒體,。不過(guò)這種內(nèi)生學(xué)說(shuō)缺乏有力證據(jù)。
夏威夷馬諾大學(xué)及俄勒岡州立大學(xué)的研究人員利用多種相關(guān)的計(jì)算機(jī)程序,，將線粒體及SAR11的基因組與多種真核生物的基因組進(jìn)行了比對(duì),，并對(duì)基因組進(jìn)行了非常復(fù)雜而又全面的系統(tǒng)進(jìn)化分析，結(jié)果發(fā)現(xiàn)線粒體與海洋細(xì)菌SAR11有進(jìn)化關(guān)系,。
研究人員表示,，這一發(fā)現(xiàn)激動(dòng)人心，意義十分重大,。夏威夷海洋與地球科學(xué)和技術(shù)學(xué)院海洋生物研究所的研究人員邁克爾認(rèn)為,，從生理學(xué)上講，SAR11更容易依賴(lài)于其他生物,，由于SAR11現(xiàn)在大量存在于海洋中,，因此其祖先在古代海洋中可能也非常豐富，這就增加了其祖先與原始真核生物相接觸的機(jī)會(huì),。
除了發(fā)現(xiàn)線粒體和SAR11之間的進(jìn)化關(guān)系外,，研究人員在以系統(tǒng)進(jìn)化為基礎(chǔ)評(píng)估基因組多樣性的研究中還發(fā)現(xiàn)，豐富的海洋細(xì)菌SAR11具有遺傳多樣性,。研究人員下一步將繼續(xù)研究SAR11的新菌株及基因組,，進(jìn)一步了解其新陳代謝能力以及為什么它們會(huì)在海洋中如此成功地生存。 （生物谷Bioon.com）
doi:10.1038/srep00013
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PMID:
Phylogenomic evidence for a common ancestor of mitochondria and the SAR11 clade
J. Cameron Thrash, Alex Boyd, Megan J. Huggett, Jana Grote, Paul Carini, Ryan J. Yoder, Barbara Robbertse, Joseph W. Spatafora, Michael S. Rappé & Stephen J. Giovannoni
Mitochondria share a common ancestor with the Alphaproteobacteria, but determining their precise origins is challenging due to inherent difficulties in phylogenetically reconstructing ancient evolutionary events. Nonetheless, phylogenetic accuracy improves with more refined tools and expanded taxon sampling. We investigated mitochondrial origins with the benefit of new, deeply branching genome sequences from the ancient and prolific SAR11 clade of Alphaproteobacteria and publicly available alphaproteobacterial and mitochondrial genome sequences. Using the automated phylogenomic pipeline Hal, we systematically studied the effect of taxon sampling and missing data to accommodate small mitochondrial genomes. The evidence supports a common origin of mitochondria and SAR11 as a sister group to the Rickettsiales. The simplest explanation of these data is that mitochondria evolved from a planktonic marine alphaproteobacterial lineage that participated in multiple inter-specific cell colonization events, in some cases yielding parasitic relationships, but in at least one case producing a symbiosis that characterizes modern eukaryotic life.
