美科學家合成出迄今最簡單生命形式

US scientists have stripped life back to its bare essentials — creating a synthetic microbe with the absolute minimum genetic information needed to grow and reproduce.

美國科學家將生命的多餘部分剔除，只留下最基本的要素，由此創造出一種合成微生物，這種合成微生物擁有生長和繁殖所需的最低限度的基因信息。

The researchers, led by Craig Venter, the genomics pioneer, made Syn3.0, the “minimal synthetic bacterial cell”, as a follow-up to their much publicised creation in 2010 of Syn1.0, the first living cell with DNA (its genome) made from scratch using laboratory chemicals.

由基因學先驅克雷格•文特爾(Craig Venter)領導的研究人員創造了名爲Syn3.0的“最小化合成細菌細胞”，這是他們在2010年創造的曾得到廣泛宣傳的Syn1.0的後續成果。Syn1.0是首個擁有用實驗室化學品從零合成出的脫氧核糖核酸(DNA)的活細胞。

They hope Syn3.0 or its successors will provide a platform to which synthetic biologists can add genes for particular purposes, such as producing drugs or biofuels, though the more immediate aim is to understand better the fundamental biochemistry of life.

研究人員希望，Syn3.0或其後續樣品能提供一個平臺，供合成生物學家加入有特定用途的基因，比如生產藥品或生物燃料的基因，儘管Syn3.0更直接的目標是更好地理解生命的基本生化機理。

The project, published in the journal Science, took four years longer than expected, Dr Venter said, and revealed “surprising” gaps in biological knowledge.

這個項目的研究成果發表在《科學》(Science)期刊上。文特爾博士表示，該項目持續的時間比預期長了四年，揭示出生物學知識中存在“令人吃驚的”空白。

The initial approach was to design a minimal bacterial genome using all the information available from the scientific literature, but that failed. The failure shows that “our current knowledge of biology is not sufficient to sit down and design a living organism and build it”, he said.

這個研究團隊最初的思路是利用科學文獻中提供的所有信息，設計一種最小化的細菌基因組，但這條路沒有走通。文特爾博士說，這次失敗證明“我們目前的生物學知識，不足以讓我們坐下來設計一個活的有機體並將它造出來”。

Instead, the team went back to Syn3.0, which was based on Mycoplasma mycoides, the naturally occurring bacterium, and began the long process of discovering which of its 901 genes were essential for life by finding out what happened when each one was deleted.

後來，該團隊調整了思路，轉而研發基於絲狀支原體的Syn3.0。該團隊展開了漫長的探索，通過逐個剔除再觀察結果的辦法，觀察絲狀支原體的901個基因中有哪些是必不可少的。絲狀支原體是一種天然的細菌。

One by one the unnecessary genes were eliminated until the team, working in California at the J Craig Venter Institute and Synthetic Genomics, its associated company, was left with 473 genes essential for replication and growth.

就這樣，不必要的基因被一個接一個地剔除，最終得到了473個複製和生長所必需的基因。該團隊的研究工作是在美國加州約翰•克雷格•文特爾研究所(J. Craig Venter Institute)及其附屬公司合成基因組學(Synthetic Genomics)展開的。

The DNA encoding these 473 genes, amounting to 531,000 chemical “letters” of genetic code, was then synthesised in the lab and the resulting synthetic genome transplanted into the shell of M capriolum, another bacterium whose own DNA had been removed.

編碼組成這473個基因的DNA，相當於53.1萬個基因代碼化學“字母”。這些DNA隨後在實驗室中被合成出來，合成出的基因組被植入另一種細菌山羊支原體(M capricolum)的殼中，該支原體自身的DNA已被移除。

The synthetic genome took over the biological machinery of the host cell, producing a healthy bacterium that reproduces rapidly in lab cultures and doubles its colony size every three hours.

該合成基因組接管了宿主細胞的生物學運作，產生了一種強健的細菌，該細菌經實驗室培養可迅速繁殖，菌落規模每三小時翻一番。