Antibacterial gene transfer across the tree of life.
Antibacterial gene transfer across the tree of life.
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DOI：
10.7554/elife.04266
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发表时间：
2014-11-25
期刊：
影响因子：
7.7
通讯作者：
Bordenstein SR
中科院分区：
文献类型：
--
作者：
Metcalf JA;Funkhouser-Jones LJ;Brileya K;Reysenbach AL;Bordenstein SR
尽管水平基因转移（HGT）很普遍，但基因和类群的可转移率存在偏差。奇怪的是，同源 DNA 向古细菌、细菌、真核生物和病毒的独立传递极为罕见，而且常常无法用生态和功能解释。在这里，我们证明细菌溶菌酶家族在不同环境中独立整合到生命的所有领域，在植物和古细菌中产生唯一的糖基水解酶 25 胞壁酶。在热液喷口古菌与细菌竞争者共培养期间，胞壁酶转录上调。此外，重组溶菌酶以剂量依赖性方式表现出广谱抗菌作用。与抗生素抗性基因的细菌转移类似，强效抗菌基因跨通用树的转移似乎赋予了一种超越生态位的适应，克服了所有领域平行 HGT 的障碍。这些发现还首次表征了古细菌中的抗菌基因，并支持在这一尚未充分探索的群体中寻找抗生素。 DOI：http://dx.doi.org/10.7554/eLife.04266.001 生物从父母那里继承了大部分遗传物质，因此基因往往从一代传给下一代——从祖先传给后代。然而，有时 DNA 会通过其他方式从一种生物体转移到另一种生物体。这些事件统称为水平基因转移，在自然界中相当常见。基因在不同物种之间以及不同生物体群体之间传递。例如，赋予抗菌药物耐药性的基因已从一种细菌转移到另一种细菌，其他基因也从细菌“跳跃”到植物或动物。现在梅特卡夫等人。研究了一种最初出现在细菌中的基因，该基因编码一种称为溶菌酶的酶。这种酶会分解细菌细胞的外壳：这是细菌繁殖和分裂成两部分所需的步骤。当梅特卡夫等人。他们寻找溶菌酶基因的亲属，在许多其他细菌物种中发现了该基因的拷贝，并揭示了该基因已在不同细菌之间反复转移。溶菌酶基因家族的成员也至少四次“跳出”细菌并进入其他生物体。梅特卡夫等人。在植物、昆虫、多种真菌和生活在炎热的深海喷口的单细胞微生物（称为古细菌）中发现了相关的溶菌酶基因。一个基因家族在生命之树上如此广泛地传播是以前从未见过的。然而，由于 DNA 是所有生物的共同生物语言，因此所有接受了溶菌酶基因的不同物种很可能会将其用于类似的目的。梅特卡夫等人。表明溶菌酶可用作抗菌分子。古细菌溶菌酶可以杀死多种细菌；当该基因被转移到大肠杆菌中时，只有使溶菌酶基因发生突变使其变得无用的细菌才能生存。梅特卡夫等人。还表明，如果存在细菌，古细菌会产生更多的酶，这使其能够在竞争中胜过这些细菌。这些发现表明，可能有许多水平转移的基因对多种细菌具有抗菌活性。寻找这些基因——尤其是在很大程度上尚未开发的古细菌中——可能会揭示治疗细菌感染的抗生素药物的新来源。 DOI：http://dx.doi.org/10.7554/eLife.04266.002
Though horizontal gene transfer (HGT) is widespread, genes and taxa experience biased rates of transferability. Curiously, independent transmission of homologous DNA to archaea, bacteria, eukaryotes, and viruses is extremely rare and often defies ecological and functional explanations. Here, we demonstrate that a bacterial lysozyme family integrated independently in all domains of life across diverse environments, generating the only glycosyl hydrolase 25 muramidases in plants and archaea. During coculture of a hydrothermal vent archaeon with a bacterial competitor, muramidase transcription is upregulated. Moreover, recombinant lysozyme exhibits broad-spectrum antibacterial action in a dose-dependent manner. Similar to bacterial transfer of antibiotic resistance genes, transfer of a potent antibacterial gene across the universal tree seemingly bestows a niche-transcending adaptation that trumps the barriers against parallel HGT to all domains. The discoveries also comprise the first characterization of an antibacterial gene in archaea and support the pursuit of antibiotics in this underexplored group. DOI: http://dx.doi.org/10.7554/eLife.04266.001 Living things inherit most of their genetic material from their parents, so genes tend to be passed on from one generation to the next—from ancestors to descendants. Sometimes, however, DNA is transferred from one organism to another by other means. These events, collectively called horizontal gene transfer, are fairly common in nature; genes have been passed between different species as well as between different groups of organisms. For example, genes that confer resistance to antibacterial drugs have transferred from one species of bacteria to another, and other genes have also ‘jumped’ from bacteria to plants or animals. Now Metcalf et al. have studied a gene that first arose in bacteria and that encodes an enzyme called a lysozyme. This enzyme breaks down the outer casing of a bacterial cell: a step that is required for a bacterium to reproduce and divide in two. When Metcalf et al. searched for relatives of the lysozyme gene, they found copies in many other species of bacteria and revealed that this gene has been repeatedly transferred between different bacteria. Members of the lysozyme gene family have also ‘jumped out’ of bacteria and into other organisms at least four times. Metcalf et al. found related lysozyme genes in a plant, an insect, many species of fungi, and a single-celled microbe (called an archaeon) that lives at hot, deep-sea vents. A gene family being spread this widely across the tree of life has not been seen before. Nevertheless, as DNA is a common biological language to all living things, it is likely that all the different species that have received a lysozyme gene might use it for similar purposes. Metcalf et al. reveal that the lysozyme could be being used as an antibacterial molecule. The archaeon lysozyme can kill a broad range of bacteria; and when the gene was transferred into Escherichia coli bacteria, only the bacteria that mutated the lysozyme gene to render it useless were able to survive. Metcalf et al. also revealed that the archaeon microbe produces more of the enzyme if bacteria are present, which allows it to outcompete these bacteria. These findings suggest that there may be a number of horizontally transferred genes that have antibacterial activity against a wide range of bacteria. Searching for these genes—particularly in the largely underexplored group of archaea—might reveal new sources for antibiotic drugs to treat bacterial infections. DOI: http://dx.doi.org/10.7554/eLife.04266.002