2012年11月21日 訊 /生物谷BIOON/ --近日，刊登在國(guó)際雜志Molecular Systems Biology上的一篇研究報(bào)告中，來(lái)自杜克大學(xué)的研究者表示,，他們開(kāi)發(fā)出了一種工程化細(xì)菌,，其可以通過(guò)犧牲自己而立于別的細(xì)菌群體的生長(zhǎng),，這同時(shí)也揭示了程序性的細(xì)胞死亡對(duì)于細(xì)菌群體的生存變得具有特殊的優(yōu)勢(shì),。
研究者Linchong You表示，我們使用了一種人工的生物途徑來(lái)檢測(cè)了大腸桿菌發(fā)生程序性細(xì)胞死亡的優(yōu)勢(shì)性,。這種檢測(cè)系統(tǒng)比較具有協(xié)調(diào)性,，使得利它死亡的細(xì)菌的范圍可以增加，因此研究者就可以控制控制程序性細(xì)胞死亡的范圍,，就和不同條件下檢測(cè)利它死亡的范圍一樣,。
程序性的細(xì)胞死亡和細(xì)菌對(duì)壓力效應(yīng)相關(guān),，比如對(duì)氨基酸的饑餓或者競(jìng)爭(zhēng)性分子的存在。然而細(xì)胞為何在沒(méi)有給與細(xì)胞任何優(yōu)勢(shì)的情況下,，細(xì)胞會(huì)選擇死亡的原因,，研究者并不清楚。一些研究者表示,，程序性細(xì)胞死亡使得細(xì)胞為生存的細(xì)胞提供好處,，但是目前到現(xiàn)在，在實(shí)驗(yàn)中并不能檢測(cè)到這種情況的存在,。
本文研究中,，研究者使用人工生物學(xué)方法對(duì)大腸桿菌進(jìn)行工程化操作，使得大腸桿菌細(xì)胞可以進(jìn)行自殺行為以及促進(jìn)其余細(xì)菌群體的生長(zhǎng)繁殖,。研究者引入了一個(gè)基因回路,，其包括兩個(gè)模塊，當(dāng)細(xì)菌面對(duì)抗生素6-氨基青酶烷酸時(shí),，如果“自殺”模塊激活,，其會(huì)導(dǎo)致一些細(xì)菌細(xì)胞死亡破裂,，如果“公共利益”模塊處于表達(dá)激活狀態(tài),，那么一種修飾的β-內(nèi)酰胺酶就會(huì)產(chǎn)生，其會(huì)保護(hù)存活的細(xì)菌細(xì)胞免于抗生素的分解和殺滅,。當(dāng)酶從細(xì)菌細(xì)胞中釋放出以后,，這種保護(hù)作用才會(huì)開(kāi)啟。
研究表示,，有可能在某些情況下,，一些細(xì)菌細(xì)胞的死亡會(huì)對(duì)所有的細(xì)菌群體帶來(lái)益處。研究結(jié)果對(duì)于理解處于壓力條件下細(xì)菌細(xì)胞發(fā)生程序性細(xì)胞死亡的進(jìn)化動(dòng)力學(xué)有很大幫助,，而且為開(kāi)發(fā)新型的抗菌療法具有明顯的應(yīng)用價(jià)值,。（生物谷Bioon.com）
編譯自：Engineered Bacteria Can Make the Ultimate Sacrifice for the Good of the Population
doi:10.1038/msb.2012.50
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A functional selection model explains evolutionary robustness despite plasticity in regulatory networks
Naomi Habib1,2,3,a, Ilan Wapinski4,5,a, Hanah Margalit2, Aviv Regev5,6 & Nir Friedman1,3
Evolutionary rewiring of regulatory networks is an important source of diversity among species. Previous evidence suggested substantial divergence of regulatory networks across species. However, systematically assessing the extent of this plasticity and its functional implications has been challenging due to limited experimental data and the noisy nature of computational predictions. Here, we introduce a novel approach to study cis-regulatory evolution, and use it to trace the regulatory history of 88 DNA motifs of transcription factors across 23 Ascomycota fungi. While motifs are conserved, we find a pervasive gain and loss in the regulation of their target genes. Despite this turnover, the biological processes associated with a motif are generally conserved. We explain these trends using a model with a strong selection to conserve the overall function of a transcription factor, and a much weaker selection over the specific genes it targets. The model also accounts for the turnover of bound targets measured experimentally across species in yeasts and mammals. Thus, selective pressures on regulatory networks mostly tolerate local rewiring, and may allow for subtle fine-tuning of gene regulation during evolution.
