据物理学家组织网报道，生存在日本温泉中的一种嗜热细菌或许可解开高等复杂生物体早期进化的谜团，并可能成为21世纪生物燃料生产的关键。相关研究报告发表在《公共科学图书馆·生物学》杂志上。
分子生物学教授艾伦·兰博维兹介绍说，内含子是进化过程中的一种神秘元素。直到20世纪70年代，各界都普遍认为所有生物体内的基因都是连续的，其由此能组成一个连续的RNA（核糖核酸），并可被翻译成连续的蛋白质。然而，包括人类在内的大多数高等真核生物并未遵循上述猜想。反之，高等生物大部分的基因都是不连续的，其由DNA（脱氧核糖核酸）编码区域组成，中间则由内含子隔开。
为了更好地了解内含子的早期历史，科研人员将此次的研究的重点放在细菌上，因为他们相信细菌是内含子进化的源头。作为唯一已知的增殖原理与高等生物十分相似的细菌，科学家对细长聚球藻（藻青菌的一种）着重进行了研究。
生物化学家格奥尔格·摩尔表示：“我们并不能回溯至10亿多年前去观察早期真核生物中的内含子是怎样增值的，但我们能够探究允许内含子在这些生物中增殖的机理，并尝试推断它们在真核生物中进化的过程。”
在对机理的研究过程中，科学家认定高温在内含子的增殖过程中扮演了关键的角色。如嗜热细菌所处的温泉，就可解开基因组中的DNA链，使内含子能够更轻易地嵌入基因组中。
兰博维兹表示，由于地球在十多亿年前正处于高温环境，且是早期真核生物出现的时段，因此DNA解链的证据对于设想早期真核生物如何增殖来说具有相当意义。这些生物最初或许只含有小部分内含子，但随着时间推移，高温可促使内含子快速地增殖。
而对于细长聚球藻中的内含子进行探索，或许也可为利用嗜热细菌来提升生物燃料效能的研究者提供意外的帮助。嗜热细菌十分善于将纤维素转化为乙醇，但其在基因操控领域却十分棘手。而嗜热内含子的发现，可快速解决这一难题，科学家可借助Ⅱ型内含子进行基因标靶。研究人员目前已经开始探究能否从基因角度设计嗜热细菌，以试图增加纤维素生物燃料的产量。(生物谷Bioon.net)
生物谷推荐原文出处：
PLoS Biol. doi:10.1371/journal.pbio.1000391
Mechanisms Used for Genomic Proliferation by Thermophilic Group II Introns
Georg Mohr1,2,3, Eman Ghanem1,2,3, Alan M. Lambowitz1,2,3*
1 Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America, 2 Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas, United States of America, 3 Section of Molecular Genetics and Microbiology, School of Biological Sciences, University of Texas at Austin, Austin, Texas, United States of America
Mobile group II introns, which are found in bacterial and organellar genomes, are site-specific retroelments hypothesized to be evolutionary ancestors of spliceosomal introns and retrotransposons in higher organisms. Most bacteria, however, contain no more than one or a few group II introns, making it unclear how introns could have proliferated to higher copy numbers in eukaryotic genomes. An exception is the thermophilic cyanobacterium Thermosynechococcus elongatus, which contains 28 closely related copies of a group II intron, constituting ~1.3% of the genome. Here, by using a combination of bioinformatics and mobility assays at different temperatures, we identified mechanisms that contribute to the proliferation of T. elongatus group II introns. These mechanisms include divergence of DNA target specificity to avoid target site saturation; adaptation of some intron-encoded reverse transcriptases to splice and mobilize multiple degenerate introns that do not encode reverse transcriptases, leading to a common splicing apparatus; and preferential insertion within other mobile introns or insertion elements, which provide new unoccupied sites in expanding non-essential DNA regions. Additionally, unlike mesophilic group II introns, the thermophilic T. elongatus introns rely on elevated temperatures to help promote DNA strand separation, enabling access to a larger number of DNA target sites by base pairing of the intron RNA, with minimal constraint from the reverse transcriptase. Our results provide insight into group II intron proliferation mechanisms and show that higher temperatures, which are thought to have prevailed on Earth during the emergence of eukaryotes, favor intron proliferation by increasing the accessibility of DNA target sites. We also identify actively mobile thermophilic introns, which may be useful for structural studies, gene targeting in thermophiles, and as a source of thermostable reverse transcriptases.
